54093052 a solar water heater workshop manual

8/6/2019 54093052 a Solar Water Heater Workshop Manual

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TEXT BY: Ken Eklund, with David Baylon, Belinda Boulter,Stuart Gustafson, Bruce Lampcov, and Randy SkoogGRAPHICS: Carol ObertonEDITING, LAYOUTAND TYPING: Annie Stewart and Richard Sassaman

Based on the Ecotope/RAIN Solar Workshop Manual of September 1976,by Ken Smith and Lee Johnson, including their substantial revision work.Special thanks to Christopher Mattock of Solar Design and ApplicationsLtd., Vancouver, B.C., for sharing design information and permissionto use the graphics noted below.

(The f a 2Zowing drawings, Z&ted as numbered in the text, are from thepre2imGaaq draft of a book on so2ar water heaters by Chxis Mattockfor B.C. Hydra, and are used with the authors permCssion: the figureor; page 5, and f


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Why Build A Solar Water Heater?How Does A Solar Water Heater Work?Will A Solar Water Heater Save Money?How To Build And Install A Solar Wate r HeaterStep By Step InstructionsMaterial 3Alternative DesignsHow To Site Yol!r Hot W ater SystemYour Collector and the CodeLocation Options and ConsiderationsThe System's PipingActive Systems

1256

1023242736373653

Freeze ProtectionHeat ExchangersCommercial SystemsMaintenanceHot Water ConservationWhat Happens When There's No Sun?Organizing A WorkshopToolsAccessFurther ReadingFeedback

57606466

67697077788081


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Right now we are changing the way we use energy,and the kinds of energy we use. Lately there hasbeen an emphasis on conserving energy, while atthe same time plans are being put forward for massexpansion of production in order to supply energyat our present use levels. We are developingenergy sources-- coal. nuclear, oil shale andsolar in all of its forms (wind, plant fuel,direct, and electricj-- different from thoserecently rel ied upon.The cost of energy has climbed and will continueto increase. This is due mainly to the restrictedsupply of conventional fuels and the high cost ofelectricity from electric generating plantsoperated by heat (thermal plants). Thiselectricity is expensive because of the largeconstruction costs and because only about 40%of the heat energy put in comes out aselectricity.Since we are in an important time of change, wehave the opportunity to make both better use ofenergy and to find better sources.

Better Uses of EnergyWhat is commonly called conservation is reallyan effort to stop the leaks, to eliminate waste.But we can also do an incredible amount ofconserving by eliminating the amount of unusuableenergy we create. We can do this through matchingthe energy source to the most appropriate energyuse, The idea here is that we first determine theminimum amount of energy needed to do a specificjob, and then find an energy source that cansupply the energy needed for the job while losingthe least amount of energy along the way.

Lets say we have two energy sources that cangive us the sam e amount of enerpv-- one cubicfoot of natural gas and one days collectedenergy from one ft2 o f solar collector. (The actuzivalue depends on the month, the geographicallocation, and the position of the collector.)We want to heat our water for washing dishes andbathing.The natural gas burner operates at iOOOF., whilethe solar collector operates at 120F. (onceagain depending on several factors). The gasburner will lose more heat than the collectorbecause the hotter an object is, the more heatit will give off to thz environment. So, eventhough the cubic foot of natural gas containsthe same amount o f energy as the square foot ofcollector will supply per day, we will have toburn more natural. gas to compensate for the heatit gives off to the environment. As you can see,our low temperature solar collector is moreappropriately matched to the job of heating waterthan is the natural gas flame.Another way to better use energy is to decentralizethe process of converting energy into forms fordoing work. This can offer opportunities to usewaste heat and will cut transportation andtransmission costs.Better Sources of EnergyOur present fossil fuels are:1) nonrenewable;2) environmentally harmful in extraction,transportation and use, and3) require expensive and centrally locatedefforts to extract and transport.More desirable sources would :1) be renewable;2) have a low impact on the environment in allphases of production and use;


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3) be converted as closely as possible to thepoint of energy use;4) be labor intensive rather than capitalintensive (make jobs); and5) be controlled by the people who use it.

Solar EnergySolar energv iJJ its various forms can qualifyboth as a better source and a better use of energyin many appl icut ions. Individual, on-sitecollection systems (like ollr water heater) cansupply heat at temperatures adequate for spaceand water heating with simple. direct conversionof light to heat -- without using greatertemperatures than we need for the job.Electricity can be produced by the directconversion of the mechanical energy in windthrough windmills or (in the future) throughquantum conversion, as in photovoltaic cells.lligh temperatures can be supplied by focusingcollectors and by fuels supplied from growingplants. tlowevcr, if we attempt to supply al 1of our energy needs by constructing large, hightemperatu re electrical generation facilitiespowered by the sun, we could run into many ofthe problems associated with our present fossilfuel technology.So how do we begin implementing a better energysolution? Stopping waste is an important stepno matter what else we do. Coupled withconservation, we can begin to take advantage ofthe suns energy. The solar water heating systemdescribed in this manual is a concrete projectthat can supply energy to help reduce your waterheating bill-- the reduction in your bill willshow the contribution to conservation that youare making.

By building and installing the water heateryourself, you will save one-half to two-thirdsthe cost of a high quality commercially availablesystem, and still receive three-quarters of theenergy tha t the best systems can give you. Youwill also gain an understanding of solar energyand of how your system works-- plus the skillsand experience acquired in building and installingit that you can get no other way.

How Does a Solarater Heater Work?First, some basic terms:

Heat: the form of energy whose effect is therel3tive motion of molecules.Temperature: the measure of the degree of theeffect of heat.BTU (British Thermal Unit): the amount of heatneeded to raise the temperature of one pound ofwater one degree Farenheit. (In the metricsystem, heat energy is now measured in Joules.One BTU= 1,055 Joules.)The major rule in heat transfer is the SecondLaw of Thermodynamics: heat will flow from warmerbodies to cooler ones. The greater the temperaturedifference, the greater the heat flow. There arethree pathways for this transfer of heat:1) Convection is the transfer of heat by the massmovement of the heated particles. An example isa cool breeze on a hot day.2) Radiation is a net transfer by electromagneticwaves that will be given off by particles withhigher heat, and absorbed by particles with less


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heat. An example of this-- warming yourself infront of a fire.3) Conduction is the transfer of heat from oneparticle to another by direct contact. An exampleof this is burning your finger on a stove.All solar systems must have som e kind of collectorto catch solar energy (which arrives mainly in theform of light) and convert it to heat. Solarsystems must also have some way to move the heata.nd a way to store it until it is needed. Thereare many different ways to do each of thesethings, but we will focus here on the systemdescribed in this manual.The CollectorTo capture solar energy, our system has a flatplate collector. This consists of an absorberplate that absorbs sunlight and converts it toheat . And since the absorber; plate is hotterthan the surrounding air, we must surround itwith an enclosure that insulates the back andsides of the plate. The enclosure has a clearcover to admit sunlight while keeping theoutside air from cooling the plate.This enclosing box helps prevent heat loss tothe air and to surrounding objects. Our collectorwill still lose heat to convection currents thatform inside the box, to conduction, and toradiation through the glazing. The hotter thetemperatu re inside the box, the I;lore heat itwill lose.Heat is transferred for use or storage by a fluidthat flows across o r through the absorber plate.In our collector, this fluid is a liquid flowingthrough a grid of copper tubes that are fastenedto the plate. The liquid then carries heat off

by the convection current.For the collector to work most efficiently, thefluid should be a lot cooler than the absorberplate. It then has a greater capacity to takeup as much heat as possible from the absorber.No matter what the temperatu re of the liquid, ittakes the same amount of energy to raise it agiven number of degrees. But if the liquid iswarmer, more heat will be lost to the atmosphere.Usually the liquid will be either water oranti-freeze solution. Wate r is a very efficient1 ollector fluid because it takes a relativelylarge amount of energy to heat-- in other words,it has a good capacity for absorbing energy. Butin many situations, a non-freezing collectorfluid must be used. These vary in theirefficiency at absorbing energy.The SystemWe now have a collector panel, but it is only onecomponent in a system needed to make the energyit collects usable. There has to be a way tostore the energy, and also ways to move it around.Storage in our system is an insulated tank thatreceives the heated liquid from the collectoroutlets and supplies cooler liquid to thecollector inlets. It is also the point at whichthe heat is transferred to the household hotwater system.Two basic approaches to transporting the h.eat are:1) those relying on the natural thermal formsfor operation (called passive), and2) those requiring outside energy inputs tooperate pumps and controls ehat move and directthe cooling liquid (called active).


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A) Solar energy passes t.hroughthe glazing and strikes theabsorber plate, where it isconvcrtcd to heat energy./ C) lleat is conducted fromthe absorber panel to thewater. The liquid risesB) The hot absorber plate loses through the absorber pipessome of its energy by COndUCt ion, as it gets hot, and carriesconvection, and radiation. The the heat away.glass and insulation help to cutdown heat loss.

D) The less dense hot water rises to the storagetank. The cooler water falls to the bottom ofthe collector and is reheated.:Iot water is siphoned off the top of the storagetank for use. Cold city water enters thestorage tank when hot water is used.


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The system we recommend wherever it can be usedis a passive natural flow system called athermosiphon. It is less expensive than anactive system because it requires no pumps orcontrols to make it work. Because it is lesscomplex, it is easier and cheaper to maintain.The driving force behind the thermosiphon isconvection. Colder water in the bottom of thestorage tank sinks to the bottom of the collectorpanels. As it does this, it pushes up thewarmer water (which is lighter) in the panel.This water will rise into the storage tank,creating the circuit demonstrated-__ ---.-- - -_ below.

ar atester ve Money?

To analyze an invcstmcnt in solar energy, severalimportant vari lhles must be consider-e. :1) The cost of the system.2) l!lc cncrgy gcncratcd (saved) by that system.3) The cost o f that energy at present.-1) The cost of that energy in the future.5) The interest rates and inflation rates

;ISSOCated with the investment.

Using these variables, a payback period can becomputed. The payback period is the number ofyears of energy savings required to cause thesystem to break even, and return in energy savingsthe invested capital plus interest.In general, if this payback period Js less thanthe life of the collectors (20 years), then theinvestment is justified. Payback analysis is a1 ife cycle cost procedure that gives economiccomparisons based on a common set of assumptionsabout the future. Different assumptions yielddifferent results.

The Economics of Solar Hot WaterThe use of solar panels for water heating presentsone of the most cost effective means of using flatplate solar collector technology in theNorthwcstclimate. This is largely because the demand forhot water is fairly uniform year round, and theflat plate collector can be used in late spring,summer and fall to produce virtually all the hotwater required by a residence.The variation in costs, however, makes carefulselection of a collector more critical. Ingenera 1 , a durable collector without costly frills[such as selective surface coatings, sophisticatedglazing configurations or other amenities) has aneconomic payback period of eight to 12 years. Theextras have their place, but generally it is asunnier climate that provides their justification.These more expensive systems when used for waterheating have payback periods of 12 to 20 years.Table 1 summarizes the payback periods associatedwith a system similar to the one built in thisworkshop.


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Table 1Cost Payback for Solar Water Heaters--

Co1 lector- ---Paybackcost $/kWh Period(years)

do-it-yourself $600 .006 7.9Ecotope collector.___________ ------.-em---.----- -------contractcr-installed $1500 .015 14.5Ecctope collector

.--------__----- -- ------- ---------standard kit $1000 .OlO 11.2collector system

____-_ --- ____- ---_--------v--T-------standard systemcontractor-installed $2000 ,020 17.2

Assumption: 15-year loan at 10%; fuel costdoubling by 1984; 7% inflationrate/year; current cost ofelectricity $ .017/kW h.

The annual savings will vary substantiallythroughout the region, depending on amount ofhot water use, locality, and the other fuel used(i.e. natural gas, electricity) for heatingwater. In the Pacific Northwest, savings may bebetween $50 and $100. In areas where electricityis expensive and the climate is sunny, such asCalifornia, the annual savings could be as highas $200 each year.The economics of solar water heating are alsoimproved by the U.S. federal tax credits. Youmay write off 30% of the cost of your collectoron your income taxes.

These payback periods will vary-- if you are notborrowing the money, if you reduce your hot waterusage, if you insulate your hot water tank, or ifyour electricity cost differs from those assumed(which is likely). The paybacks represent acomparison. If you change these assumptions,it will reduce your payback period for alloptions. For instance, if you do not borrowmoney to pay for the system, then you willcut the payback periods in half.

We will now begin describing how to build andinstall a flat plate solar collector. Directionsfor building the collector are specific becauseit can be used in different types of installations.But installation can vary tremendously dependingon climate, site, money and a number of otherthings. So we have tried to give an idea ofdifferent considerations and solutions, theiradvantages and disadvantages, along with specmaterials and details for the options we havedeveloped . Active systems are discussed in alater chapter.

ific

These collectors are designed to be constructedand installed by people with general buildingskills, using ordinary tools from readilyavailable materials at reasonable cost. Thismeans tin effilast aand ifmanual.

hat the collectors cannot be the ultimateciency and durability. But they willlong time if care is put into buildingmaintenance is done as prescribed in this

Develop sment has been done on the basis ofexperience with the collectors, on both collectorconstruction and installation, and freezeprotection systems. We hope you will share your


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aideat; and experiences with us. Theres a form atthe back of this manual for you to give us feedback

Materials PurchaseWe have done our best to give you a completematerials list for collector construction.Installation varies too much for us to givecomplete directions or a specific materials list.But we have identified special items andmanufacture rs so that you can find them. Thematerial quantities in the collector instructionsare for one panel (except for paint).The section on piping lists items basic to anysystem. The freeze protection discussion givesa fairly specific idea of what is needed forthe option you choose.To build and install these collectors, you willbe buying la rge quantities of copper tubing andplumbing supplies and glass. Try to get themwholesale--shop for good prices. Be especiallycareful when you buy glass. Prices vary greatlyand the unwary m ay be taken. If you have troublegetting materials and hardware a t reasonableprices, consider forming a buying club with yourneighbors so you can buy wholesale.Wherever possible, use recycled materials. Tanks Iglass, even wood and pipe can be found for freeor almost nothing. The design may have to bemodified to take advantage of recycled materialssuch as tempered glass. If you use recycledmaterials be sure they are in good condition.

Collector Design and ConstructionOur panels have undergone a lot of development.

We changed from steel pipe to copper tubing tomake use of easier soldering connections and toincrease hea t conductions. We tried various waysof binding the tubes to the plate: thermal masticdid not hold up well and solder bonds brokebecause cop per expands more than steel. We havealso found corrosion at the solder joints. Wenow wire the tubes to the plate.The insulation has been changed from Styrofoamtmto fiberglass batts. The fiberglass is cheaper,more available, and does not evaporate in highheat as the Styrofoam was found to do.The glazing detail has been changed to make useof new materials. Instead of caulk thatdeteriorates rapidly, we are now using butylglaziers tape, which is very easy to installand holds up well. We arc now experimentingwith some new inner glazings and methods ofapplication, But the general approach is stillthe same: to build a box with standard sizelumber that is strong enough to support itself.A separate cover is used to make the collectormore easily transportable (two lighter piecesrather than one heavy piece) and to facilitateservicing the collector plate.

To make the collectors as durable as possible,be sure to prime and paint them carefully. Ina workshop setting two coats of exterior latexare the only feasible treatment. In both casespressure treated wood should be considered.

Glazing: Some NotesGlazing is the transparent or translucent materialused to cover the solar collector. Thisglazing can be rigid like glass, semi-rigid like


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fiberglass-reinfo rced plastic (Kalwall ,I Filon,Lascolite), or thin, flexible film-likepolyethylene, polyester (Mylar), and polyvinylfluoride (Teflon, Tedlar).Glazing primarily must allow light rays from thesun to enter the collector, and prevent heat fromleaving. Hence, the two most important featuresto consider are maximum transmission of solarradiation (i.e., short-wave or ultraviolet) andminimum loss of heat radiation (i.e., thermal,long-wave or infrared). Other important factorsare the useful life of the material, the easeof installation, and cost.Two influences on the ability of the material tolet light through (solar transmissivity) arereflection and absorption of light rays by theglazing material. Reflect ion should be kept toa minimum, It is important that the glazingr?ateri.al accept both direct radiation from thes.un and a large percentage of diffuse light fromthe whole sky.Diffuse light is especially important in aclimate with relatively few completely cleardays (like the Maritime Northwest). Fiberglasshas a comparatively high reflectivity (especiallyof diffuse radiation), while glass and polyvinylfluoride have lower reflectivity.Absorption of light rays by the glazing materialcan be caused by impurities in the material, butit is most often due to changes in the materialschemical structure. Exposure to ultravioletrays, air pollution and heat can cause thesechanges. Materials most likely to change arepolyethylene, acetate, Mylar and vinyl. Glassis almost completely unaffected by these problems.Glazing-grade fiberglass is usually treated to

withstand ultraviolet exposure. If you use it,make certain it has been factory-treated in thisway.Most common glazing materials are poor reflectorsof thermal radiation, although some (like glass)can absorb the hot infrared rays and re-radiatepart of them to the interior. Glazing usuallydoes not keep heat in by reflecting it, but bysuppressing the convection of air currents. Twolayers of glazing are commonly used because airtrapped between the two layers is not allowed toconvect in the small space between them. Theair space thus acts as insulation and goes a longway toward preventing heat losr. Three layersof glazing can be effective in very cold ciimates.but the added 1 ayer will also reduce lighttransmission and raise the cost of the collector.IVe have already mentioned that some glazingmaterials have greatly reduced transmijsivityafter pro longed exposure to light, heat orpollution. Many also physically deteriorateeither because of ultraviolet radiation ormechanical stress.Glass, although resistant to the elements, is verysusceptible to breakage by hail, birds, orvandalism. Tempered glass can reduce this probler,considerably. Fiberglass is very vulnerable tosurface erosion unless it is specially treated.Fiberglass will also sag under heat expansion andsnow loading unless it is corrugated to addrigidity.Films can stretch or becom e distorted, creatingstress and. breakage. Polyethylene, though cheap,has a very short lifetime and will virtuallydisintegrate when exposed to weathering. Acrylicplastics, though very break resistant, expand toomuch to be desirable in a solar collector that


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Table 2Qualities of Glazing Materials

Glazing Material:shortwave longwave* relative

transmission transmission f environmental cost**c% of total! (% of total) stabilityRigid:

w1nJov RI"" a?%- -varies 3-8. excellent medium-l/8 wirh lend if not highcontent broken______________________ --e-_----7- -.-- ----------------tempered glass similar to 3-a, excellent highwindok breakageglass resistant____________ ---B-e-------.-------- __-__---___- e---macrylic -- l/A about 855 3% pmi+ hlCh(Plexlglas5l------~___--- ____ _______ -_-_---VW-----.--------- _.------__Acrllyte FM as?, 3% good+ high(douhlr sl,lnned

acyllrlSemi-Rlqid:

regular fIberglass about 70% 6-l% poor mediumflat - 15 m:l---- _______ ____ ____ - __________ --------m-----e-----pol)T:nyl flillll.IJc- -9: -8% fair medium-ccm1rJ it,rruf.it c.4 highf.hcrglass--30 mil(FI 1~. Larcoll lel

Films:polvcth>Icqe 70-88% 7n-RIIO. roe:, 1OW4 ml1 (6 !nonths)________________ ___- ____- ---- -----0-e ------------po1yestcr about 85% 1 1 6 - 3 ? 18 pd lOk-5 ml; mechanically; medium

(Mylar1 good II\resistance-______________________^___I -__-__----_--~~~-~~~~--poly\~nyl fluoride 90-94: 43% Tzflcvl: lov-4 ml1 excellent medium(Teflon. Tedlar) Tedlar:mechanicall!poor ; good U\resistance

*Longwav? transmission is onl!, one of several measures of ho* wella material keeps hear from escaping. None of these really gives acomplete picture. This measure *as chosen for slmpllcity and consistency.**Cost varies greatly with source of supply.

tAcrylics have a high coefficient of linear thermal expansln!A. Acrylitewill expand abour l/E in a 4 panel wit h a 20 temperature rise.

9may get hotter than 100 F.The way a glazing material is attached to theframe will have a considerable effect on its lifespan. Glass must be mounted perfectly level, andproperly bedded to allow for its expansion andcontraction.Large, unsupported sheets of rigid m aterials tendto be fragile. They are also most difficult toseal properly. Thin films, on the other hand,must be carefully protected from wind flap andtearing. They should be evenly clamped withstrips of wood or metal, or reinforced ifstapled. Tedlar works best when shrink-fitted ata high temperature and clamped with a mechanicalbond such as a channel and locking strip. (Thisis a commercia l process.)Cost will probably play a part in your choice ofglazing, although it should be balanced againstthe expected lifetime of the material.If you are using two layers of glazing, as werecommend, you will have different considerationsfor each layer. While the need for maximumtransmissivit]? of solar radiation remainsconstant, the inner layer should also be chosenspecifically for minimum transmission of thermalradiation. Although the inner layer m ust stillbe resistant to changes from ultraviolet raysand heat, it will be protected from most othersources of damage by the outer layer, and can bemuch thinner. The outer layer should be chosenespecially for good weathering ability and strength.


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Materials

one 8 2x6, standardtwo 8 2x6, standardone tube ofBui lder s Adhesive8 - #10x2/, flathead,galvanized wood screwsone 4x8 sheet 3/8CDX plywood$ lb. 6d galvanizedcommon nai 1s12 of lx4 molding(it need not be clean fir--use any kinll of 1x,1)6 - (1 0x22 fwoodscrcws lathcad

L gallon exterior latexpaint -- or if time permits,an enamel primer

1.1

lnstructlonsSTEP ONE: Build BoxCut two 45 pieces of 2x6 to form frame ends.The other two 8 pieces form the sides.Form the pieces into a 4*x8 rectangle, !&I deep.Make sure the comers are square and join themwith Builders Adhesive, then screw to secure.Apply Builders Adhesive around one edge ofthe frame. Set the plywood sheet on top(this will be the bottom of the box) and nailaround the edges using 6ds to secure.Turn the box over.Cut three 45 lengths of 1x4 to form braces.Apply Builders Adhesive to ends and bottoms ofbraces. Place them across the inside bottom ofthe box at 23$ intervals.Screw at sides and nail from the bottom.

Figure 1

1.2 Paint box inside and out. If time permits, it isbest to prime with enamel prim er and then paintwith exterior latex or enamel. Otherwise, use 2coats of latex. Pressure treated wood can also beused for longer life.

1001s

:ape measure:ri- square; hand saw;;aw horseslrill and bitscrewdriver ; hammer:aulk gun

Measure twice, cut once!

paint brush


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three 10 lengths of lx3Fir

zlueten #8x1$ galvanizedFlathead woodscrews4d finish nailspaint from Step 1.3

STEP THREE: Side and Paintthe Glazing FrameThe purpose here is to side the glazing frame to make acover for the box. The comple ted cover should fit snugyet come off easily.

3.1 Cut two pieces of fir to the length of the frameplus 3/4.Cut one piece to the width of the frame plus l&.Cut one piece to the width of the frame.3.2 Set glazing frame built in Step 2 onto the collectorbox. Drill pilot holes in side pieces.Screw and glue side pieces to the frame as shownin Figure 4. Put finish nails between screws tostrengthen.

3.3 Paint completed cover.

Figure 4

crosscut saw, table,radial arm orcircular saw

bit E drillscrewdriverhammer

paintbrush


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2 ft2 of R-11 foilbackediberglass insulationIf only 16 width is avail-dble instead of 24, cut 6pieces to length. Cut 2in half to fill the boxes.)

:wo 8 1x20* corrugatedgalvanized steel roofing10 - #6& galvanized;heet metal screws

vinegar, galvanized metalpreparation or a weaksolution of muriatic acid

one pint flat blackename 1, high quality, hightemperature (recommend:Rustoleumt, or Sherwin-Williams industrial flatblack)*

4.1STEP FOUR: Install Insulation-Cut fihm-assW2&1and fit itbetween the1x4 supportsinstalled inStep 1.1.Foil side up!

STEP FIVE: Screw Collector SheetsTogether, Etch and Paint5.1 Cut the steel sheets to 88% long and trim width tofit in the box when joined (about 44 -45) . Scrapsmay be saved for use in Step 13.5 2 Punch holes 9. apart at lap.Screw sheetstogether.

5.3 Etch topsurface ofgalvanizedmetal. Applyvinegar, allowto stand, thenbrush or scrub.Rinse and dry.5.4 Paint absorber sheet. The lighter the coat applied,the better the heat absorption characteristics.

utility knifegloveslong sleeve shirt

tape measuretin snipsmetal punch or powerdri 11; tape measure;screwdriverutility brush

paint brush or spraypainting equi-pment(compressed or airless)


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r

three 20 sections of2 rigid copper tubing,Type M

flux14 - 3/4x3/4x+ coppercopper tees(15 if the collector is tobe used in a bank)

STEP SIX: Cut Pipe and Fit Tees6.1 Cut two 89 lengths from each 20 section of coppertubing (that is, make 6 lengths). Cut and ream theinside of all cuts as shown in Figures 7 and 8.

Figure iYou should have three 62 remainders.Take one of these and cut it into two 27 lengths.Clean and flux couplings and join each 27 piecewith a 62 remainder to make two more 89 lengths.You should now have a total of eight 89 lengthsto be used as risers.Refer to the section on Piping (page 46) and planthe layout of the piping now. Use a 3/4-to-$reducing elbow at the blind corner of the grid.Use tees at inlet and outlet corners.

6.2 Clean and flux tees and elbows.Fit them to the tubing ends.

tape measuretubing cutter withreaming blade (or usea pocket knife)

medium gauge steel wo(utility brush forapplying flux


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7 of 3/4 rigid coppertubing, Type M for manifoldflux

one roll of 50-50 soldernot acid core(2 lb. of solder is more thanenough for 2 collectors --usually enough for a wholeinstallation)

.f

Fi

STEP SEVEN: Cut Nipples to Connect Teesand Form Manifold; Solder Pipes

7.1 Place wipes from Step 6 in every other valley ofthe corrugated sheet. Measure between tees to checknipple length -- usually 4 3/4 works perfectly,allowing for socket distance inside tees. cut,clean, ream and flux 4 3/4 nipples and fit intotees to form manifold. (See Figure 9 in Step 8)

7.2 When all of the tubing grid is completely assembled,and with the 3 pipe still lying in all the valleysof the corrugated sheet, solder all end joints.After the end joints have set, slide the twocoupling joints clear of the absorber plate sothey can be soldered.7.3 Clearly mark the grid and plate to assure exactreassembly, by cutting an identifying mark on the

absorber plate and filing a shallow mark on a copperT. The bottom of the panel and its locationrelative to the other collector should be identified.To solder, heat fitting at joint with inner core of flameuntil solder melts when touched to it. Be sure not tooverheat the joint -- if the solder boils, it is too hot!Allow solder to flow into the crack between fitting andpipe. Check joint. Do all joints on the same fittingwith the same heating. Use a minimum of solder. If youfeed too much, it will run into the pipe and restrictwater flow. Dont move joint before solder sets. in, 201quickly pour on water.

ape measureubing cutter wearning blade ith

ropane torcheveral damp rags

ilein snips


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flux; solder3 of 3/4 rigid coppertubing, Type Mtwo 3/4x3/4 copper malethread adapters (sweat fit)two 3/4 capsone valve, 3/4 bronzeone hose adapterone roll Teflon pipe sealtape

STEP EIGHT: Test for Leaks8 l Cut four 9 pieces. Ream and clean ends.Flux and solder to open end of corner tees.8.2 Solder thread adapters to two diagonally oppositecorner nipples. Solder caps to remaining corners.8.3 Using Teflon pipe sealer, attach 3/4 valveto one corner and hose adapter to the opposite corner.Attach hose and pressure test for leaks. If thereare leaks,drain completely, heat joint at leak andadd solder ,

Figure 9

tape measuretubing cutter withreaming bladepropane torch; rags12 adjustable wrenchor large pipe wrenchor large channel-lockpliersgarden hosetwo gallon bucket


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one or two 3/4 coppersweat fit capsfluxpaint from Step 4

one roll 16 gauge copperlockwire(galvanized or stainlesssteel will also work)

STEP NINE: Prepare Grid to Put in BOX9.1 Remove valve, adapters, and caps from thecorners by heating the adapte r sweat joint andpulling off.9.2 Refer to Piping section and determine the precise

layout of the installation. Determine the positionof the inlets and outlets to the grid. Shortenand cap the corner nipples which will not be used.9.3 Clean all flux from the pipe grid.Rough the surface with steel wool. Paint thegrid with a brush or spray application.

STEP TEN: Attach Pipe Grid toAbsorber Platelo.1 Place pipe grid on absorber plate.Punch holes no more than 1, apart on either sideof 1, pipes every 6.10.2 Insert wire and fasten the pipe to the absorberplate. Since the wire is lightweight,use minimal force.

propane torch

pipe cuttersolder equipment

medium coarse steelwool ; spray paint gearor paint brushes

metal punchhammer

wire cutterspliers


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STEP ELEVEN: Cut Notch for PipeLocate inlet and outlet locations by laying absorber/grid over the box. Mark sides of notch with tri-square. Mark bottom of notch at 2.Cut notches in the box for cold water inlet andhot water outlet nipples. Save wood notch cutoutsfor re-use.Cut notches in sides of the cover to match notchesin the box. These need to be 3/4 deep.

six #8x1? galvanizedroundhead screws 12.1

STEP TWELVE: Screw Absorber PlateInto Box

Place absorber plate tubing grid assembly into the boxPunch pilot holes in every fourth valley of the plateand 1x4 supports. Screw elate to su~aorts

ri -square:nci 1rill or brace with18 bit; crosscut saw;4 wood;od rasp chisel;hammer;

metal punchhammer


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caulk and gluewood notches from Step 10nailsmetal scraps from Step 5

cover bui It in Steps 2 and 38 of 48 wide !i or 1 milTeflon glazing30 of lx1/8 neoprenesponge weatherstrippingone box 3/S staplesone box 9/16 staples(both heavy duty)fiber strand tape3M H463 adhesive transfertape, 3/8 wide

.3.?-3.2

14.1

STEP THIRTEEN: Seal NotchesRefit and glue wood notches. Caulk area around inlet

Icaulk gunand outlet pipes to stop heat loss and water hammer and tin snipsinfiltration.

Flatten sheet metal scraps fromStep 5 and cut to make two l$x6strips. Nail strips over woodnotches to hold in place.At this point, you may want tomove colZectors to place ofinstallation.

STEP FOURTEEN: Install Inner G-lazing(Optional)Apply adhesive transfer tape around glazing frame.Apply Teflon glazing to it, pulling tightly andsticking it first at midpoints of opposite sides, thensmoothing toward corners while still stretching tightlyand avoiding ripples. Now cover edges with fiberstrand tape for reinforcement. Staple through thistape with shorter staples (3/8), then apply neoprenegasket and staple it with the longer staples (9/16).

Figure 13

I

Figure 12

3ui Id ing stapler


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!5 of 21Tx31 L-flashing:or get 5 flat and bendit yourself)

30 of Y butyl glazing tape2 sheets of 48x48 doublestrength glassor 48x98 Lascolitetm orFilon fiberglassglazing material4 plastic mirror clips4 brass screwsone tube of sili.cone caulk

STEP FIFTEEN: Install Outer Glazing-5.1 Set cover onto collector box.

Cut a 48 length of flashing. (If bending ityourself, clamp to a table and bend as shown inFigure 14.)

tape measureti.n snips

Place 2 leg of flashing over lower edge ofglazing frame.15.2 Lay glazing tape on flashing and on top of theglazing frame where glazing will rest. (Hint: pressdown on paper backing with one hand while pulling upwith the other.)15.3 Lay glass onto frame, leaving l/8 spacein the center between the two sheetsof glass. Make sw-e it rests onthe glazing tape at aZZ edge points.Secure bottom edge of glasswith four mirror clips. Use brass screws instead ofplated screws which come with mirror clips.15.4 Run a bead of sealant between glass sections.

Ii


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flashing from Step 15

si iicone caulk

20 butyl glaziers tape14 - #6 x Z/4 brass orhot dip galvanizedroundhead woodscrews

STEP SIXTEEN: Install Flashing16.1 Cut one 56 length and two 96 lengths of flashingfor upper end and sides. Bend flashing to the angleshown in Figure 13. Prepare flashing by cuttingnotches to match notches in cover sides and make

overlapping corners at the top as shown inFigures 16 and 17.

Figure 16clip sharp corners of flashing to avoid nasty cuts!Apply silicone sealant or roofing compound to thejoint to seal it

16.2 Punch sixteen l/8 holes in the sides of theflashing (the 3 flashing leg). Holes shouldbe l? from the top and 18 apart.16.3 Apply butyl glaziers tape 1% from the edge ofthe glass. Place flashing in position and screwflashing to the sides of the cover.Apply a dot of silicone or butyl caulk to eachhole before inserting the screw.

tape measuretin snips

caulk gun

metal punchhammer

screwdriver

r -T


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8 - l;i x 1% hot dipgalvanized lag screws:en I;ii. d. x qo .d . washers)utyl or silicone caulk

STEP SEVENTEEN: Screw Cover to BoxInstall the glazing -- especially if using glass -- asclose to the installation location as possible.If collectors must be moved, remove the cover to make,the weight more manageable.

17.1 Drill & hole in the side flashing l+ii from the top,two on each side.Screw cover to box sides.Seal as in Step 16.3.drill1, bitsocketsratchet / I

17.2 Cover exposed wood in notch slots with caulk.

.&cs+-==- h

This list is for one collector. aterials


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Double the quantities as necessaryfor two collectors.f Lumber:3 8 2x6 #2 fir1 4x8x3/8 CDX plywood32 llx2 clear fir (two 10; one 12)30 lx3 clear fir (three 10 pieces)12 l~4~ fir (need not be clear fir,

but must be knot-free)Building supplies:

1 tube silicone caulk1 quart marine resin glue, plastic(recommend: Wi lholdl)1 tube Builders Adhesive32 ft2 R-11 fiberglass insulation, foilback,24 wide (if only 16 width isavailable, cut to widthwith utility knife)25 2x3 L-shaped flashing(or get 5 flat and bend it yourself)2 8 sections, galvanized steel roofing,corrugated , thinnest gauge available1 pint flat black high quality, high tempera -ture enamel paint (recommend:Sherwin-W illiams wrought iron flatblack or Rustoleum t,)+ gallon exterior latex paint(or enamel primer, if time permits)

Miscellaneous and specialty supplies1 quart vinegar or galvanized metal prepara-tion or weak solution of muriatic acid2 sheets 48x48 double streng th glass (option:48x98 Lascolitetm or Filontm fibe r-glass glazing material)81inear Teflon film, 1 mil, 48 wide (at least)1 roll % butyl glaziers tape1 roll cellophane tape

Hardware supplies: \$ lb. 4d finish nailsk lb. 66 nails, galvanized14 #10x2$ flathead woodscrews12 #6x3/4 flathead woodscrews10 #8x1% flathead woodscrews

6 #8x1+ galvanized roundhead woodscrews10 #6x& sheet metal screws14 #6x3/4 brass or hot dip galvanizedroundhead woodscrews4 brass screws sized to replace screwsthat come with mirror clips1 roll wire 22 gauge stainless steel or16 gauge copper or galvanized4 plastic mirror clips1 box 3/8 heavy duty staples1 box g/16 heavy duty staples

30 fiber strand tapePlumbing supplies:

3 20 sections $ rigid copper tubingType M10 3/4 rigid copper tubing, Type M14 3/4~3/4x+ copper tees(15 if used in a bank)3/4-to-L+

(: if to be used in-a bank)copper elbow2 3/4 copper sweat-to-3/4 maleNPT adapter2 &I copper coup 1 ngs2 3/4 copper caps1 3/4 bronze globe valve1 hose adaptersmall can of flux, not acid(or use lsolder in flux)1 roll SO-SO solder, not acid core(+ lb.) (this is more than enough for 2 col-lectors, usually enough for a whole

installation)small roll Teflon tape pipe thread sealer


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The collector weve just shown you how to buildhas been the subject of much development and,recently, of a lot of study. It is being testedin the U.S. Departmen t of Energy collectortest program. It is also a component in thethermosiphon system whose performance is beingstudied as part of our water heater researchproject funded by the National Center fo rAppmFria te Technology. If the collector israted favorably by DOE, the design may qualifyfor loans, credits, and other good treatmentproducts of the solar industry receive. Ouraim, though, is not to link do-it-yourselftechnology to a few standard designs, but tooffer a proven example of it that gives aquality alternative to buying a commercialsystem.Keep in mind that the collector weve justshown you is only one design-- though aproven one. It can be used as a basis fora solution to water heating that usesmaterials you have available or that meetsa specific design requirement you have.There are many opportunities for improvementin details, and for substitution of componentmaterials in the basic flat plate collector.A few ideas will be discussed here to showyox what can be done.A minor modification that simplifies theworkshop collector and allows for a cleanerlooking installation is the running of theinlet and outlet pipes through the back ofthe collector. The pipes are made to runat an angle toward the top of the collectoras shown opposite. This detail eliminates the

complexity of making cuts in the box and coversides and shelters the pipe from exposure.Another modification is to change the absorberplate. One popular alternative has been to usealuminum roofing sheets with grooves on 8 centers.The G risers of the grid fit into the groove andare held in place by wire. Fewer risers are usedbecause of the wider spacing, thus reducing cost.Efficiency is lost because the aluminum has ahigher therma l conductivity than steel and is inbetter contact with the riser, It is importantto have a layer of paint between the copper andaluminum, and to use stainless steel lockwirebecause of potential corrosion problems.Another option with the absorber plate is to buyone that is commercially malde. Often if group


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orders are made they can be bought for a priceequal to or cheaper than the cost o f the do-it-yourself. However, if you are building athermosiphon system you will have to find out ifthe plate you are buying will work, because mo stcommercial absorbers are designed for pumpedsystems that can have higher flow resistance.Another thing to consider is that the absorberplate size may require a modified box size.The glazing is another componen t that can beexperimented with. Although the double-strengthglass used in the collector described is widelyavailable, highly transparent and relatively cheap,it also has a tendency to break-- which is a realproblem in areas subject to hail or other highimpact fallout. Tempered glass is much tougherand can often be bought cheaper as factory secondsthan regular double-strength glass, and work finefor solar collectors. These sheets come instandard sizes-- generally 28x76, 34x76 and46x76) and cannot be cut, so a collector usingthem will have to be made to fit.It is often suggested that sealed , double-paneinsulating glass windows be used to give instantdouble glazing to the collector. Two things arelikely to happen. The first is that the seal islikely to leak and allow water in between theglass panes, causing fogging. (Drill ing ventholes in the edge might solve this.) The secondis that the inner pane of glass may shatter dueto high thermal expansion obstructed by the edgeseal.The other glazing option is to use a solar-gradefiberglass. These can be lighter and cheaperthan glass and are unbreakable, though theirtransmissivity tends to be lower than glass and

may decrease as time passes. In areas with a lotof sun this wili not be a great problem. Thismat-m-ial_..---A --A comes in a..--LWU fOlrnS-- fiat and corrugated ~If flat sheets are used,its rigidity can begreatly increased by bowing it with curvedendpieces. If this is not done, fiberglass maysag onto the absorber plate under snow or athigh temperatures. If corrugated sheets areinstalled, a special piece of material calledwiggle board I must be used to seal the ends asshown in the figure below.

In using either type of fiberglass, the edge isbedded on a bead of silicone caulk, nailed downand flashed for weather protection.The size and shape of the box can be changed toaccommodate a different glazing material or


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absorber plate or to meet a special situation asshown on page 43. When changing the box size,care must be taken not to waste lumber. Forinstance, if a 76 length is used to take advantageof low-cost tempered glass seconds, the sides canbe cut out of one 14 2x6 with less waste than ifcut from two 8 2x6s. Generally speaking, if thesame area is contained in smaller boxes, morematerial will be used. So build the largest sizeyou can, while still keeping a manageable sizefor handling.The collector design in the instructions uses 2x6sides to take advantage of self-insulation andto make a collector that will support its ownweight. It is possible to make the whole co llectorfrom plywood-- if carefully planned, a smallersize collector box may be made from one sheet ofplywood. Strength and durability will only beobtained if reinforcing nailer strips and glueare used. (Plywood edge grain does not offermuch of a hold to nails or screws.) Because theabsorber plate and glass are heavy, the collectormay have to be supported by the mounting stand,which may reduce savings obtained by using lesswood in the collector.The collector box does not have to be built withwood, though that is usually the material that iseasiest for most people to work with. Sheetmetal can also be used if the skills and toolsare available. Another approach would be to usestandard steel framing pieces to form the sidesof the box, allowing the box to be bolted together.The major design problems here are to be sure theabsorber plate and pipes do not touch the box,and to insulate the sides as well as the back ofthe box. The most feasible insulating materialis polyurethane foam. Care must also be taken toproperly prime and paint the metal to prevent rust.

Rigid insulation board can be used, but it ismore expensive than fiberglass batts. One- inchpolyurethane foil-back board is possibly the bestmaterial available at this time. As withfiberglass, be sure to put the foil up. Ifunfoiled board is used, put on a layer ofaluminum foil. Styrofoam t, has proven itself tobe incapable of withstanding temperatures higherthan 200 F, which occur when the collector isstagnated (not cooled by water flow). This mayoccur if the collector isnt covered when itsnot working. Never put loose fill insulation ina collector; it will wander all over the collectorand is likely to absorb moisture.This book focuses on flat plate collectors withparallel-tube fluid channels. There are manyother designs available, from flat platecollectors with serpentine fluid channels tobatch-type heaters such as bread boxes and roofponds. Some of these are referenced in theFurther Reading section.


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The prime consideration in the siting of a solarhot water heater is the availability of sufficientsun1 ight. The greatest amount of this energycomes from the direction of the southern sky(if your s o ar heater is in the northernlatitudes). Of course, everything is reversedif you are locatil?g south o f the equator. Priorto making other design decisions, a site surveywill show you whether there is enough sun toproceed.The Site SurveyWalk around your site and become familiar with theobvious obstructions to the sun. At this time,it is valuable to make note on a pad of the typesof obstructions and their ownership (e.g., aneighbors house due south or deciduous treeson the sites property that might block the sunwhen in full leaf). If you number these comments,these numbers can be used to mark your Sun PathChart.Once you have a good idea o f potential obstructions,you should walk around the site or crawl carefullyaround your roof while imagning yourself to be asolar collector panel. Think of yourself waiting

anxiously for enough sun to keep you as warm aspossible during every month of the year, thinkingsomething like, "Here I am freezing on this roof(or down here on the ground) waiting for the sunto come out from behind tha t evergreen tree."Remem ber that in the winter the sun is much lowerin t?le sky than in the summer, and that you aretrying to maximize your warmth evenly throughoutthe year. When you think you have found the bestof several possible locations for available sun,ask yourself, "What would it be like here?"Is the collector far away from where the heat willbe needed? Long runs of pipe will make all ofyour hard-earned heat get lost in transit. Willit be very difficult to mount on the roof? Willbaseballs from the local playground keep hittingit? After you have considered all the things thatmight get in your way-- and you still think thisis the right place-- it is time to plot theskyline on the Sun Path Chart. (See Fig. 20.)


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Sun Path ChartThe Sun Path Chart shows the suns locationduring different times of the day and year.It is used to determine what the potentialblockages to light from buildings and terrainwould be at the proposed solar collectionlocation. The chart is made by projecting thesuns apparent motion onto a sheet of paper.Figures 21 and 22 show how this is done. Thechart included with this manual is for 48north latitude. Seattle and Spokane, as wellas Fargo, ND, Duluth, MN, and Quebec City arevery close to this. Sun charts for otherlatitudes in the U.S. are available in The SolarGuide and Calculator. (See Further Reading. )The position of the sun in the sky (or anyobject, for that matter) is located by measuringtwo angles that describe it in terms of itsrelation to true south and the horizon. Theseangles are called the solar azimuth and thesolar altitude.Along the bottom of the sun path chart runs thesolar azimuth, the measurement of an objectsposition in degrees of arc relative to true south.True south points directly to the South Pole.Objects are-measured in terms of their positionrelative to true south, because the sun ishalfway through its trgvel across the sky whenits azimuth angle is 0 (true south). (Pig. 23)

Figure 22


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at Figure 20

bW"AUG APRIL 21

20

, IO0

\ !/ I/\ I I O01200 1054 go0 75O 60 45O 30 15 0 15 30 45 60 75 90 1050 1204- wcnzt EAzTE cl-f Angle from True South tfaetz Wr3J-cC~7(Azimuth)


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Sun Path ChartThe solar altitude runs up the sides of the sunpath chart. It is the angle of an object inrelation to the horizon. The sun is at itshighest altitude when its azimuth angle is O,which occurs at midday as noted above. (Fig. 24)The arcs on the sun path chart are marked w iththe dates on which the sun would trace this pathacross the sky, with the highest arc on June 21(summer solstice), and the lowest arc onDecem ber 21 (winter solstice). Solar time isshown by the numbered and dotted lines. Notethat the suns azimuth angle is Oo and itsaltitude angle is maximum at 12:00 for all timesof the year. (The standard time at some locationswithin a time zone can differ with the solar timeby as much as l& hours.)

Figure 24

tv NOONIII I

700i-l

RL-i -kf24&B ] i- , -71 1--r- ; ;j-l / 500i_1,-

31

LO jq- qg. 1105 IW 135 150 vw5- ,,xJ- 195. Zld U5. 240. .?55 Z?O ,?n5- m

123 IUJ ,I,- Is- D- I>- .xJ- 15 0 15 30 4Y 60 75 9P IC5 IZC.f t+.-


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The skyline that you see when standing at thecollector site is plotted on the sun path chartso that you can determine which objects willblock the sun and when they will. To plot theskyline, you must locate each object in terms ofits azimuth and altitude angles. We willdescribe here how to plot these two angles, andgive an example of how a tree would be plottedon the chart. (See figure 31.)First, stand where you want to put in yourcollectors, face south, and pick the highestpotential obstruction to the sun in your view.The altitude angle of the object can be measuredwith either a transit, or more simply, with aprotractor and a plumb bob. (Fig. 26)

Treat the 90 marking on most protractors as 0Count the number of degrees between the stringand your 0 to find the degrees above thehorizon (altitude). For our example, the topof the tree has an altitude angle of 45O. Makea note o f the altitude angle so it can be usedlater for the plot.

The azimuth angle is measured with a compass.Compasses are made so that all objects aremeasured in terms of north instead of south.Therefore we will h&ve to first measure theobjects location ill terms of true north (thedirection of the North Pole), then convert thatnumber to a south azimuth angle. (Perhaps whensolar compasses are made they will have the redneedle pointing to the south!)

Figure 27 ,


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To find the location of the object with respectto true north:1. Point the direction-of-travel arrow towardthe object. (See figure 27.)

The magnetic needles north end either pointsfarther east than true north (east deck ination)or farther west (west declination). Thedeclinations for locations in the United Statesare m arked on the m ap below. Seattlesdeclination is 22O east.2. Turn the dial until the North reading linesup with the needle pointing to magnetic north. Magnetic Declinath Adjustment

Figure 283. Read and note the bearing from the dialdirectly over the direction-of-travel arrow.The compass (Fig. 28) indicates that the treeis 160 east o f magnetic north.4. Convert the magnetic bearing to a true bea ring.As you've probablv guessed by now, there are twokinds of north, magnetic north (the direction acompass needle points in) and true north (thedirection of the North Pole). Magnetic north andtrue north are not the same in most locations.Since the magnetic field varies and moves slowlyover the earths surface, it is necessary toknow the difference for your locale betweenmagnetic and true north (called the declination).

DELLINATION-3 .W

Once you know your declination, you can calculatethe true bearing from the magnetic bearing in thefollowing way: when magnetic bearing is east oftrue north (that is, when you are west of the Oodeclination line shown on the map) subtract thedeclination from the magnetic bearing to producethe true bearing. When the magnetic bearing iswest of true north (when youre east of Oo), addthe declination to find the true bearing. (Fig. 29)


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For our example, since Seattle is 22 east, thetrue bearing is:160 - 22 = 138

( de~~~~~:fon) (b~~~~g)

The tree is therefore 138 east of true north.To find the azimuth, simply subtract 180 fromthe true bearing.138O - 180 = -42

( t~e~~fn~hl CCOIl~~l~OIlj (eas;t;fjbearing

Note: if you obtain a negative number, yourreading is east of true south. A positivenumber is west of true south. (Fig. 30)

iNI Figure 30

Now we have it! The tree has ar azimuth angleof 420 east of true south. Now we can plot thetree (or your particular obstruction) on thesun path chart. To do this, mark the point onthe chart represen ted by the altitude and azimuthangles (42O east, 4S-- that is, the top of thetree). The rest of the tree can be sketched in,or you may measure directly other points of theobstruction the same way the top was measured.Go through this procedure for all obviousobstructions, and then fill in every lS of solarazimuth to complete the skyline. Now you willhave to determine whether or not this representstoo much shading.Not all the areas on the sun path chart are asvaluable for solar heat as others. This ispartly due to the greater amounts of atmospherethat low-angled sunlight must pass through, andpartly due to the particular climate of your area.An example of this latter effect would beconsistent morning fog that would make aneffective shadow covering the early morning(easterly) area of the chart. A detailed analysiscould be done hour-by-hour using The Solar Guideand Calculator (see Further Reading) andinformation about your local weather patterns.A more simplified approach follows here.The area in Figure 31 outlined by the heavy linecontains virtually all of the energy in a clearsky. So, if your skyline does not come up intothis area, you need not be concerned with shadowingof your collector. If it does come into this area,then try to get an idea of the percentage of thearea obstructed. The lower section (Area A) contains40% of the energy and the upper section (Area B)contains 60% of the energy.


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38/85

Qrientation of the CollectorSince hot water is used fairly evenly throughoutthe year, we will want to pick a collector tiltthat will give tne best year-round performance.This is approximately equal to the latitude,in Seattle roughly 45O-48O. This assumes thatno reflector is incorporated into the design,as with this workshop.Reflectors can be used to considerableadvantage if the collector location canaccommodate them. The reflector can result inincrease in collection of sunlight by thecollector surface. This increases output fora relatively small addition to the system cost.For a good discussion of this, see EnhancedSolar Energy Collection Using Reflector-Sola rThermal Collector Combinations, byMcDaniels, et al., the University of Oregon.(See the bibliography and figure 32.)

Figure 32

PermitsInstallation of a solar water heater is subjectto regulation by building, zoning and plumbingcodes. The regulation process typically involvespresenting drawings of the system with a feepayment, receiving a permit, and having thework inspected to see that it complies with theCode. The building authority has the power toforce a non-compliance project to be modifiedor torn out, though usually only payment ofthe permit fee is demanded.Although legally required, the permit processis ignored by many do-it-yourselfers. Thisapproach works fairly well where the projectis inconspicuous and/or non-controversial.Even if the project will invite inspection,if the permit might be denied or burdened byconditions some people find it to a tacticaladvantage to build first and get a permitlater.If there is opposition by neighbors or thecommunity, a Code violation can be the basisfor removal of the water hea ter. Based on theinformation given here, together with what youknow about the enforcement of the codes inyour area and attitudes toward solar collectorsin your neighborhood, you should make your owndecisions about whether or not to get a permitbefore building.Building CodesMost building codes do not specifically mentionsolar hot water systems. Their only requirementis that the installation be mounted securely andthat the roof be able to support it. Roofs areusually required to support at least 25- 30pounds per square foot at any point on the roof,


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but some points will be able to supportconsiderably more. The panels in this manualweigh about 10 pounds per square foot when full,excluding any support structure. The storage tank(if 60 gallons) when full weighs about 600 poundswithout its frame. Building inspectors may notbe too concerned about this issue, but for safetyssake, you should be. Read the Installationsection thoroughly, and plan your system so thatit will distribute t.he load stress on your roofsafely.

Zoning OrdinancesZoning ordinances are of concern because they maycontain minimum clearance requirements betweenstructures and property lines. For example, ifthe clearance requirement for a side yard is 10feet, and an installation is made closer to theproperty 1 nes , it is in violation. In onerecent case this was the grounds for forcing thecollectors to be removed when a neighbor obiectedto the glare. (Solar Age 3 (3) Marih, 19785 Forany ground installation near a property line, therequirements for the site concerned should bechecked. This is usually administered by theBuilding Departm ent as part of the permit process.

Plumbing Codes and Proposed Collector CriteriaPlumbing codes and proposed regulations dealingspecifically with solar systems have a lot ofbearing on the installation of solar hot waterheaters. Technically, any change in the watersupply in a house requires a permit in mostareas. A major point of concern is thatpoisonous antifreeze not contaminate water thatcomes out of household outlets. (See the manualsection on Freeze Prorection.) The plumbingcode is administered by the Building Departmentin most places and operates in the same way.

iePatio

Permanently installing the collectors you havebuilt is the most challenging aspect of puttinga working system together. The major considerationsare collector and tank location, safe and durablemounting and weatherproo fing details to protectthe system and your building, integrating thesystem into your regular water supply, andprotection of the system from freezing.Each situation is very different in its requirements,so it is not possible to give a specific plan,Instead, we have given a good deal of informationon these issues to provide you with the backgroundnecessary to install properly in your case. Itis highly advisable to read this en tire sectionand think about the system as a whole be fore youbuild your collectors, since you may wish tomodify the collector design. It may also behelpful to turn back to the full system schematicon page 46 for reference as you read.The first step will be to decide where to put thetank and the collecto rs. This decision isaffected by solar exposure, structural requirements,and whether you want to build a thermosiphon or apumped system. Then you will have to plan how topermanently install these components to withstandwind, rain, snow and gravity. Part of this processwill be planning where pipes will run- bothbetween the storage tank and the collectors andfrom the water supply to the point of hooking withthe hot water system. Finally, freeze protectionshould be considered at this point because it may


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influence your basic choice on whether or not touse a pumped (or active) system, and the tankposition requirements in a thermosiphon s:stem.A frequent question is whether or not the collectorsshould be installed on a stand that allows thetilt angle to be changed to follow the sunschanging altitude. The gain in collector outputif the angle is changed four times a year can beas high as 10% to 20%. However, the capabilityis difficult to build into the system.The first problem comes from trying to developa durable, leakproof plumbing connection thatcan flex to accommodate the change of position.A high-temperature silicone hose is probablythe best solution. The second problem liesin building a mounting stand that allows thecollector to move, but fastens it securelyenough to withstand wind.Wood used in collector and tank support standsmust be protected against the elements.Especially if the stand is attached to the roofit is wise to build it with pressure treatedwood. At the very least it must be wellfinished and maintained.There are basically two options for thelocation of a solar hot water heater:freestanding on the ground or roof-mounted.Either of these locations may be used for athermosiphon or a pump-type system.

FreestandingGround mounting may be chosen to provide easierorientation and installation of the collectorindependent of the house. It provides easy accessfor maintenance, inspection and disassembly. Afreestanding water heating system should be mountedonly where there is uninterrupted solar exposureat ground level.Some disadvantages to mounting a collector atground level include glare off the collector,and vandalism. Glare may not be a problem fromyour point of view, but it can certainlyantagonize your neighbors. Youll also want tobe sure your system sits within the setback1 mitations on your lot.If mounting a thermosiphon system at ground level,you will need a stand for the collectors (asshown in figures 33 and 34), a stand and insulatingcover fo r the storage tank, and piping to thedomestic water system. If .the system uses a pump,only a collector stand and piping are requiredfor installation, since the tank (which still mustbe insulated) can be located inside the buildingshell. (Fig. 35)

Figure 33


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-wExcess Capacities for Gable-Type Roofs--


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There are two kinds of load your roof must support:the live load and the dead load, The dead loadrefers to the weight of the roof itself, andanything that will be a permanen t fixture on theroof- including the collector panels and tank.Besides this, the roof must also be able tosupport a live load- such temporary loads assnow, rain, wind, and people. If you add thepresent dead 1oa.d (about 10 lbs ./ft2) to thelegal minimum live load capacity (about25 lbs./ft2) and subtract the total from thestructural capacity of the roof, tile remainderwill be the excess capacity available for thewater heating system. These are the weightsper square foot shown in the table opposite.If your roof is a properly engineered truss-typebuilt with 2x4 s, it can support an excess loadof 10 pounds per square foot.While checking the roof, you should note if thereare signs o f rot or insect damage. Rotting maybe found where there is an unventilated atticspace or a leaky roof. Damaged wood will giveto pressure on its surface or show discoloration.Don't add any load to a roof with damaged structure.

RAFTER Unbraced Span LengthSIZE 4' 6' 8' 10 12'

2x4" 76 14 don't add a 1o;d

2x6 198 78 28 don't add load

2x8 319 170 84 41 23

2x10 465 244 144 87 49All figures in pounds per square foot.

a/'

/ A&&- -tktW r,


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If the roof is in good shape and has an excesscapacity of at least 10 pounds per square foot,it can hold the relatively heavy workshop co llectorsdescribed in this m anual. Care must be taken toinsure that large amounts of snow are not allowedto build up on the collectors, which couldoverload the structure.A thermosiphon tank containing 60 gallons ofwater weighs about 600 pounds. Even with aproper cradle,20 ft2 area, the load is spread over only awhich applies a load (when theenclosing structure weight is added) of from35 to 50 pounds per ft2, It is thereforeadvisable to put the tank over a verticalcolumn brace that runs to a bearing wall.Additional braces may be added, Somesample solutions are shown in figures 40 and

Figure 40 Figure 41

In these situations it was desirable and possibleto place the tank above the collectors. If thisis not possible for either safety or aestheticreasons, then there are other options. One is toplace the tank on the same level as the collectorsand use a thermic diode (see the Piping section) toprevent back-siphoning. The other option is toput the tank below the collectors and use a pump(Fig. 42, also see section on Active Systems). Ifthe tank is placed on the ceiling joists, it iscrucial to put it over a bearing wall if theirsize is less than 2x8. (Fig. 43)

Figure 42 Figure 43

Roof Mounting StandOnce the support requirements are thought out,there are other design details to consider. Astand may have to be built for the collectors toassure proper slope and orientation. The relationof collectors to tank in a thermosiphon systemmust be planned to assure proper fluid flows. Aweatherproof enclosure wili have to be built fora tank that is located outside the roof. Finally,you must consider how water is going to be brought


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to the rooftop level, and where the pipes willrun.After a careful design is drawn out, the way inwhich it will be implemented must be planned.Stands for collectors and tank should be builtbefore they are brought up onto the roof.Safety lines on heavy objects and extremeprecaution are advisable.

An alternative to mounting the collectors abovethe roof is to build them into the roof. Thisis most easily done when bming a new house,but can also be incorporated into an existing roofwith a bit more work. The insulation and absorberplates fit in between the rafters; the glazing isinstalled much like a skylight, with full flashingrunning under the shingles using liberal amountsof roof goo. Great care is required to preventleaks.

Attaching Collectors to the RoofIf the roof angle and orientation are good,the collectors can be mounted directly to theroof structure. They must be held slightlyabove the roof surface to avoid water damage toboth roof and collectors. At the same time,they must be firmly attached to the raftersformi:lg the roof s structure.There are two basic ways to support and tie downthe collectors. One is to raise the collecto rswith brackets that are bolted into the rafters.The collectors can either be attached directlyto the brackets or can be bolted to horizontalrunners that rest on the brackets. (Fig. 44)Another way to tie down the collectors is toput nailers across the rafters and bolt thecollectors to them. This is essentially thesame thing as using runners on brackets.However, the nailer must be sloped to allowdrainage of upstream water and also be sealedto prevent leakage in the roof and rot in thenailer. The procedure is to coat the placewhere the nailer is going to go with plasticroof cement (thick roof goo) , nail the nailerin place to the rafters, then coat the upstreamedge with a thick coat of goo.

IMPORTANT Before planning the mounting system,refer tb the sktion on "Piping."

Tank SupportsIn cases where obtaining a proper angle requiresthat the collectors be tilted up off the roof,a sturdy mounting stand will have to be built.It should be constructed so that:


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1) It supports the collectors at the properangle.2) It is sturdy and firmly tied to the raftersso that it will withstand strong winds,3) It will not impede the flow of water off theroof or cause a leak.If the roof slope faces south or if it is almostflat, the solution is fairly straightforward.It is somewhat difficult to give detailedinstructions for a stand for every roof angle,because the variations in sites possible woJldmake any instructions meaningless.

Figure 45

member in contact with the roof should be treated;structural members should be angled slightly sothat water can drain from this gutter.If the slope of the roof faces east or west, t.hedifficulty of obtaining proper orientation,structural safety and architectural compatibilityis far greater, and the difficulty increases withthe slope of the roof. In these cases, a groundinstallation should be seriously considered. Butif the roof is the only feasible place, thecollectors can be modified to accommodate thesituation, as shown in figure 46. The strategyhere is to build thinner collectors that are placedon the slope of the roof in ranks spaced far apartenough to avoid shadowing. (See Fig. 473

Figure 46Figure 45 shows a stand made from 2x4s that cando the job in many situations. In building anystand, we recommend that its structure and anypart of the panels be lifted a few inches fromthe roof surface with a nailer to avoid waterabsorption and wood rot, plus water collectionon the roof. The upstream side of any support

The collectors should be placed on whichever sideof the roof receives the most sun. For i.nstance,in a region of frequent early-morning fogs thecollectors should be placed on the west slopeto take mid-day and afternoon sun. If morningand afternoon are equal they can be placed where

they will achieve the degree of visibility (or


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invisibility) that you desire- or on both slopesto collect some sunlight all day.

Figure 47

Standard tempered glass shower doors that canoften be purchased cheaply as seconds com e inwidths that could be used on a thinner collector-34 x 76. The collector box should be designedto be long (as in figure 46) in order to avoidthe increased cost of box materials that wouldoccur if the 60 ft2 of collector area werecontained in more individual collectors.If the collector is modified in this way it willhave a long side for a bottom edge. Pleaseremember that the bottom edge is made with theglazing lapped over the flashing.

Supporting StructureIn a thermosiphon system, the tank may be locatedeither on the exterior of the roof (Fig. 48) orunder it in a space higher than the top of thepanels (Fig. 49). When possible, the interiorlocation is recommended. If the ,tank must beplaced outside, we think the housing should befully sided.and flashed, making it both moreattractive and better p rotection for the tank andthe roof.

Figure 48 Figure 49

Once again, because of the diversity of situations,we cannot attempt to give specific instructions onhow to build a support stand. Any stand andenclosure should:1) Be anchored to the rafters and be able towithstand winds;2) Distribute the weight of the tank evenly tothe structure below;3) Not cause leaks or rain collection on the roof;4) Insulate the tank against heat loss and freezing;5) Shelter the tank and its insulation from water;6) Be architecturally attractive, or at least innocuou!

Materials for Mounting ,45\


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Sizing Your SystemThe average Am erican household uses 15 gallons of hotwater per person per day. A system using two of thecollectors described in these instructions will heat orpreheat a 60-gallon storage tank to usable temperature(130o-1400 F) once a day for eight to nine months of theyear in most North American climates. If your wateruse is much more than this, you will need more collectorarea and a larger storage tank.The section on Hot Water Conservation may help you t0assess your hot water usage. You may even find a wayto avoid building a larger system.

ReflectorsRather than add more collector area, you should considerenhancing the performa nce of the collectors you have bybouncing m ore light into them with a reflector. Awell-positioned one can add up to 30% more useful heatto the system during the winter.Before you put one up, build a model. This is necessaryboth to set the reflector at the proper angle to focuson your collectors and to predict where the reflected1 ght will go in the sum mer. Consider whether the lightwill bounce into a neighbors windows or will beabsorbed by shingles, curtains, or a house that istrying to stay cool. Use a flashlight to simulate thesun. With a sun path chart as a guide, you should beable to duplicate the angle o f the sun at differentseasons to test the reflectance path at those times.There are many ways to build a reflector. The simplestis to glue foil to a properly angled surface in frontof the collector with roofing compound. In some cases,the surface can be the roof (if its flat). If aspecial surface is used, be sure it is weatherproofand we1 1 -anchored.

Since every installation is different, we canon1.y give you an idea of the essentials youllneed to put the panels up.

Quantity1 30 to 40 gallon tank(The life of a new tank is about six yecrs.You can use a recycled hot water tank, pressuretested with threads cleaned and tapped.Sometimes recycled boilers are available; theyare better because the steel is much thicker.)111 or more

13

pressure relief valve, 180 psiwith long probefloat-type air vent(such as Amtrol #700)% Petes Plugs(To take temperature; see thesection on Access)3/4 silcock for draingate valves, size to fit houseinterface lines

unspecifiedquantity 3/4 galvanized close nipplesand galvanized Tsunspecifiedquantity 3/4 copper tube (rigid,Type M), copper sweat elbowsand copper TsLumber to build a stand for tank, collectors,and a tank enclosure if its required.(We recommend pressure treated wood forexposed structural elements.)Nails and other hardware as your designrequires.\


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The piping system is the transport link betweencollectors forming the collector bank, betweenthe collector bank and storage, and from storageto the water supply system. It is essentialthat you have a well-thought out plan, includingthe number and placement of inlets and outlets,before you even begin building the collectors.A major problem in the plumbing of a hot watersystem is: keeping the heat in! In planning yourpipe routes, both in the collector loop and thewater supply loop, try to run them inside theheated space as much as possible. For a roof-mounted system, run the pipes under the roofsurface rather than on top of it.his protectsthe pipes from weather extremes and allows youto use cheaper insulation on them.The roof puncture is sealed with a roof jackmade for 2 stock. The pipe is shoved throughthe stretchy collar !tlith its neoprene pipeinsulation jacket on as shown on page 24.

Figure 59Link to StorageThe first step is to find a point for the coldwater supply. This caii be as near to the storagetank as you can find it. For example, on a two-story roof system, tap into the cold water systemon the second floor rather than the basement ifpossible. The cold water supply line does nothave to be insulated until it is taken outsidethe heated space; both in the attic and outsideit must be insulated.Next, plan how to get the hot water from thestorage tank down to the point of entry into yourhot water system. This entire line will have tobe insulated (as should all hot water lines) toprevent heat loss.

Your solar system will be set up for either Bypass : A bypass system should be built to


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preheating or direct use.

Storage to Conventional System1) Preheat System: If used for preheating thehot water output from the solar storage tank willgo into the cold wa ter supply line on theconventional hot water heater as shown infigure 51.

( (Figure 51 1

you should know that if you have a gas water heater,preliminary studies indicate that solar preheatingmay save you less energy than if you have anelectric heater. This is because the efficiencyof a gas heater depends on having cold water toheat-- if the water is preheated, more of thehigh temperature gas heat goes off --instead of into the water tank. =3 waste heat,Electric waterheaters do not have this problem because theheat range is more specific to the job.

allow for operation of the conventional waterheater system without the solar collection circuit.(In order to avoid restricting the lines, allvalves used in the lines should be gate valves.)The cold water line into the water tank isequipped with a valve (A in the figure opposite)to shut it off when solar hot water is being used.The solar hot water line also has a valve (C inthe figure) to allow A to be opened withoutflooding the solar system with cold water. Thelow point on this line needs to be equipped witha shut-off plug. The cold water line to the solarstorage tank must also be equipped with a shut-offvalve and drain plug, but the line does not haveto take off at the tank as shown in this example.

Direct Use System2) Direct Use System: If solar hot water is useddirectly, you will still need to make previsionsfor shutting off the water supply to the collectorsystem. It is also essential that a temperingvalve such as a Watts 70 A be put in to avoidscalds from overheated water (temperatures as highas 180 F can occur in the storage tank on full_- -sun days)shown in

. Thefigure

The balance valve shown in the sketch (Fig. 52) is


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used to match cold sqply pressure to the pressurefrom the collector, which will be lower due toa pressure drop through the solar system.

Fluid PassageIn order to get a thermosiphon effect, itmust be possible for cold water to fall outof the bottom of the storage tank to the bottomof the collectors, and to rise as it is heatedthrough the collectors and output line into thetop of the storage tank. This cannot happenunless the bottom of the storage tank is higherthan the bottom of the collectors and the inputpoint on the storage tank is slightly higherthan the top of the collectors.llsually a thermosiphon is set up so thet thebottom of the storage tank is higher than thetop of the collectors, as shown in figures 33 E 34.The reason is to prevent backsiphoning, whichcan happen when the collector is colder than thestorage tank, and if water in the collector ishigher than some water in the tank. In thissituation, the heavier cold water in the collectorwill disFlacc hot water in the tank, pushing itout of the top of the tank back into the panelwhere it will be cooled.If the take-out point on the storage tank isplaced 12 above the top of the collectoroutlet, backsiphoning will be prevented. Heightsabove two feet will result in reduced flowrates and efficiencies.Backsiphoning can also be prevented throtlgh theuse of a device called a thermic diode (shownin figure 53) . This is a valve that will openthe channel during collection periods but close

it at other times and prevent reverse flow. Thoughthe effec t is similar to a check valve, it isoperated by temperature rather than p *essure andcan work in a thermo siphon. Check valves offertoo much flow resistance to be used in this kindof system. If a thermic diode is used, it ispossible to Lave an effective thermosiphon withoutputting the tank above the collectors, though theonly device available commercia lly at this timecosts over $100.

BlockagesIn the thermcsiphon loop it is vital that the linesrun steadily downhill from the tank to the co$lector.If the 1i::e should have a high point where ai!:can collect, an airlock may be formed that willstop the flow in the system, as in figure 54.If a high point is unavoidable, it is important toput an air b leed valve at that point.


51/85


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beyond this the flow resistance in the headersbecomes too high, and the linear expansion ofthe copper at high temperatures can breakconnections between panels.

Joining Panels to Form a BankPosition properly: The headers must rise aminimum of % for every 4 feet. This is toassure that the fluid can rise unimpeded frominlet to outlet (important in a thermosiphan),and to al low the fluid to drain from the inletpoint (important in both thermosiphon andpumped systems). Be sure to plan for this risewhen planning and assembling the collector banksupports . Check the rise with a carpenters levelJoin collectors: Plumbing unions make the bestconnection and assure that the collectors arelined up accurately. Hoses may also be used,allowing more flexibility in position andeasier movement of collectors, but are not asdurable. If hose is used, high tempera turesilicone is recomme nded.Before securing collectors, move them s,lightlyapart and solder the halves of a bronze union toadjacent headers, Move the collectors back intoposition and screw the unions to form amechanical connection. Recheck the rise andsecure the collectors to their supports.If two or more banks are used in a system,they can be connected in parallel as shown infigure 56. This also suggests how to deal withan obstruction like a dormer.

Figure 56

Drain and Temperature Measuring HardwareThere must be a drain valve at the low point (inlet)to the collectors to allow for draining the collectorloop and storage tank. The valve should be a standardsilcock with a hose thread. If you wish to be ableto drain the collectors without draining the tankyou will have to put a gate valve in the line comingfrom the bottom of the tank.It is also helpful in checking the system performance(and fun!) to put ir. scme gear that allows j-02 to,take tempera tures at different points in the system.9f most interest are the tempera tures at the inflowtank and outflow to the collector, and thetemperature of the water coming from the storagetank into the hot water system. You wi.11 probablynot want to climb onto your roo f to check thepoints at inflow and outflow, but if you have aground installation or are doing it fordemonstration purposes it will be well worth theeffort. And any system can have an easily accessible


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probe po-int on the solar hot water line beforeit flows into the house system.The device used to take temperatures is calleda Petes Plug. It is a brass fitting with aneoprene seal that allows a dial thermometerwith a l/S probe to be inserted into the pipe.The thermometer should have a range fromoo--2200 F. Figure 57 gives a sample plumbingdetail to show how inflow and outflowhardware and drain could be put together.

Lam showing use of.ple Plumbing Detail IT to integratePetes Plug

L Figure 57

0 3/4 copper tubing@ 3/4 x 3/4 x 3/4 T@ 3/4 nipples48

3/4 to l/2 female thread adapter& ;/;:;,f,,;fr; ;;;;ock

square foot the operating temperature increasesand efficiency decreases. If it climbs much


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InsulationThe lines in the collector loop and the linesconnecting storage to the water system mustbe insulated. Where the lines are outside, thebest insulation to use is 1 thick neoprenepipe jacke t such as Armaflexpainted with a coating to prot lim . It must bect it fromultraviolet light and weather; it can beslipped over the pipe during assembly or cutand glued back together with a special contactcement. Cement and protective paint will beavailable from the insulation dealer. Ifyou cannot find these items locally, order themfrom the sources in the lAccessf section.Where the pipe is well-protected from the elements,it can be insulated with strips cut from standard3% fiberglass batts tha t are stapled around thepipe. This is a bit harder to install than foamjacket, but is much cheaper and gives at leastthe same insulating value. Fiberglass wrap isnot as good.

StorageThe storage tank is the digestive tract of yoursolar system. It is here that the heat from yourcollectors must move into your dr

54093052 a solar water heater workshop manual

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