solar mounts

8/8/2019 Solar Mounts

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Residential/ CommercialSolar P V installations

Basic information and installation guides for roof mounted systems (Ed Larsen, Building Official)

May-June 2008City of Flagstaff/Project Review Section


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Design and PermitsA building permit is required for a Solar PV or thermal solar system.Staff has prepared a Memorandum (Memo #106; which is periodicallyupdated) on the submittal requirements. These permits are not issuedover-the-counter.If the system is to be connected to the grid (APS utility system), then acopy of the approved interconnect agreement and a licensed contractoris required for the final installation and green tag. For off-grid orbattery systems, a licensed contractor is not necessarily required.If the system is not roof mounted, then the arrays must be protectedfrom the general public. This can be done by establishing racks ateight (8) feet or greater above the ground level or by providing fencingor a skirting system around the underside of the panels to preventcontact with wiring.Permits are not issued over the counter, but require plan review.Simplified drawings are allowed. A one line or block schematic isrequired and a three-line wiring diagram (indicating wiring sizes and allleads) is also required.


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Design and Permits - continuedThere are some minor conflicts between Article 690 of the 2005 NEC and thewiring sizes for various breakers. The inverter specifications should be carefullycompared to the general requirements [i .e., a PV system may only require #10sor #12 AWG wiring on the AC side and the max current (amps) may be 30 orless; however, the designer goes for the maximum size for the panel of a doublepole 40 amp breaker.this requires #8 AWG wiring, ooops!Grounding is important and the use of Weib grounding cl ips to the channelsmakes it easier. One key factor is that the Weib cli ps can only be torqued once,so make sure panel alignment is correct the first time.All of the components of the solar PV system need to be UL listed andmanufactured specifically for solar installations.When combining the metal conduit with plastic or non-metallic boxes (which aresuperior on roof tops or any location exposed to weather), then grounding lugswith interconnections between the ends of the conduit needs to be used bonding requirements.


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Permit applicationThe applicant must include a copy of the APS i nter-connection agreementfor grid tied systems.

A regular residential or commercialbuilding permit application is alsorequired. The residential permit willonly include fees for the electricalitems. The City of Flagstaff does notdo a technical review for gooddesign, so the applicant must makesure that the efficiency for the systemhas been reviewed and discussed with

the designer.A licensed contractor is required for thegrid connection systems.


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Other drawings required

Both a one-line block diagram is required showing the critical components of the solar PV system (right) and a three-line drawing which indicates thesizes of conductors, fuses, disconnects, breakers, etc. These are the samerequirements for APS or the Utility company.


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Calculation worksheetThe calculationworksheet (whichcan be obtainedfrom BrooksEngineering (orother solar PVwebsites) allowsthe designer toquickly match theinverterinformation, the PVpanelspecifications,temperature & wiring sizes for theentire system. Itwill help even theplan reviewer notediscrepancies orpotential problems(recommended,but not requiredfor submittal).


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Solar definition basics*Definitions from Brooks Engineering

PV Cell The basic photovoltaic (PV) device that is the building block of PVmodules. The cell is a thin wafer of silicon which changes light into electriccurrentPV Modules - one solar cell produces 0.5 volts and 36 cells are connectedtogether to charge 12 volt batteries, pumps and motors. The new standard is 72cells per module for 24 volts and operating at about 30 volts. The module is thebasic building block of systems. The PV cells are connected in series and/orparallel and encapsulated in an environmentally protective laminateIntegrated PV Modules are often constructed to look like materials normallyfound in construction i.e., shinglesPV Array A group of panels that comprises the complete direct current PVgenerating unit. (Sometimes referred to as a string).


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Residential InstallTypical roof topinstallation uses arack mountingsystem, panels setin arrays or

strings (multiplepanels) andconduit forinterconnection of panels. Shownhere are Sharp

170s. A cell ormodule is a singlesilicon unit andgenerators 0.5volts.


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Day one of installationThe layout crew wil lmeasure the surfacearea of the roof andmust check the exactlocation of the roof framing membersbeneath. Since thepanels add atributary load of between 3-5 psf, thisextra dead load isminimal and shouldnot require astructural engineer.However, the racksystem requires thatthe anchors areembedded into theroof framing, not justthe sheathing.


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Track system and mounts

This standoffs or spacers of this Pro-Solar system is attached using 5/8 diameter, 3 long lag bol ts through the metal roofing, OSB and penetratingthe 2-1/8 wide TJI top chord webs. The holes are pre-marked and drilled.Henrys 9000 gutter and flashing sealant is used to prevent roof leakage.


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Racks and vertical supportsThe front rails willhave small restrainingclips to hold the front of each panel. Thevertical uprights [shownbehind the rail] willelevate the panel to thedesired angle for thespecific latitude of theproject. The clips areadjustable from side-to-side. For the verticalsupport legs (once cutto the correct length)also allow the installerto adjust the tilt of thelegs. This system willbe set @ 35 degrees(optimal for Flagstaff)


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Racks and vertical supports

Although installation could be done by oneindividual, a multi-crew installation makesholding the rails to the vertical supports mucheasier. These rails are aluminum and easy tocut and hold in place.


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Racks and connectionsThe spacing between thesolar PV arrays is critical.As the sun moves to themaximum height (azimuth)during the summer monthsto a lower height during thewinter months, the panelsmust not shade each other.Partial vertical shading willonly short circuit part of apanel; but horizontalshading will stop electricalproduction for the entirepanel and thus the array.The spacing needs to be

done during the designphase and prior to anyinstallation. The legs getminor adjustments usingflat washers to keep thebars level.


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Racks and connectionsThe alum. C channelshaped rails are connectedtogether and must have agrounding bond betweenthe rails. Charlie issecuring a pre-drilledconnector that will snugglyclamp two twenty footsections together. Abonding scrap, using a lockwasher straddles the twochannels and is tighteneddown. The Weeb splicersare used as the groundingis not sufficient with just

the ProSolar splice kit.


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Rack installation - continued

The installer works to keep the legs and rails plumb. Care is given during the setup stage toprevent having to disassemble or make major adjustments once the panels are installed. This systemhas a total of 33 Sharp 170 watt panels or a maximum production of 5.61 Kwh. The layout and rackinstallation took 2-1/2 days to complete (prior to installing any panels).


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First Panels going upThe first panel goes in andthe installers check theracks for plumb andalignment. There will be atotal of eleven (11) panelsper array. The Sharp 170watt panel being used hereis guaranteed for 25 years.The open current voltageis 43.2 volts, the Maxpower is 34.8 volts, theMax current is 4.9 ampsand the model efficiency is13.1% The panels weigh37.8 pounds each and are

62x32-1/2x1-3/4 insize. (array configurationdepends upon themaximum size of 600Volts, DC)(Price of panels for this installationwas approximately $725 each)


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Panel install continues

Panel arrays must be kept at the same angle (when the roof plane changes) to keep the voltage production the same. Someadjustments may be required; Kelly, Drew and Chuck arekeeping the first panel square prior to tightening the lags.


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Conduit & ConductorsConduit sizing is covered by Article 690 & 230 of theNEC (City of Flagstaff is using 2005 NEC). The boxesmust be grounded; so there are several keyconsiderations in using plastic boxes (weather proofingfor snow and water) with metal conduit. The metalconduit here uses grounding lug end connectors and

jumper wires (sized per Code) to keep the groundingand bonds of the conduit, rails, panels and boxesconsistent. This is all connected to a groundingterminal in the box adjacent to the inverter. Sizing of the wire should be based upon the panel voltagerequirements.

The proposed system would allow standard 12 gaugewiring; however, going to the next larger size (10

gauge) is more efficient and doesnt cause voltage lossto heat because the gauge is marginal or undersized.Because this is a metal roof installation, THWN 90 highheat wiring and insulation were used.


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Wiring & Connections1

2

3

4

Photos: #1, wire spoolracks with 10 gaugewiring and color codedmake the pulling of wireseasier. #2, the DC switchwith grounding and lugterminals are used toconnect the arrays to theinverter (this is a Sun Boy6000). #3, junctionboxes and conductors areelevated above the roof deck to prevent dammingof leaves and debrisduring rain and snow

storms. #4 The conduitis held up from thedecking with artificialdecking blocks (pre-drilled) and caulking;string line keeps systemaligned.


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More electrical

The inverter needs to be shaded and out of the weather. For this roof top installation, the SunnyBoy 6000 is mounted under an overhang. The inverter weighs 145 pounds and comes with aspecial mounting bracket. The owner here wanted the entire system secured and used a plywood backer that was supported by three vertical studs and secured with 12, evenly spaced 3 deck screws to hold the weight. The entire mounting board was painted prior to installation.

Electrician checks groundingbetween conduit in plasticboxes.


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Misc. connections1 2

3 4

The solar panels comepre-wired with a maleand female plugsystem. The panels are

active or capable of producing DC voltagethe minute the sun lighthits the panel.

Photos: #1 , solar cell junction box at back of panels; #2 cabling forpanels is carefullytucked into the rackchannels [care toprevent crimping of connectors under paneledges]; #3 lighteningarresting systeminstalled in junction boxahead of inverter; #4 ,conduit down to photovoltaic meter at groundlevel.


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Connection to Service panelFeed breaker may notexceed 20% of the panelservice size. This case,the house service was200 amps, this l imits thebreaker to 40 amps;max. output for thissystem is 25 amps.During final inspection, itwas determined that thewiring size (10 gauge)needed to be a doublepole 30 amp fuse orincrease the wire size to#8s for the 40 ampbreaker. Breaker waschanged.


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Conduit from roof to panel

Since this panel is exterior to the house (open to the environment), the panel needs tobe connected through the bottom of the existing service panel. The bare copper wire isconnected to the service panel grounding lug and uses the existing UFER to completethe ground.


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MeteringA digital AC power production meter is installedafter the lock out junction boxfor the system. The UtilityCompany (APS) wants thislock out accessible withoutgoing into a fenced backyard.The meter must be read oncea year and the informationsent to the Utility Companywithin 15 days.

The safety requirement for themetering is to prevent thecustomer from back feeding the grid system. If thisdisconnect wasnt there andAPS had to work on the lines,then the lines could be hot even though air-breakers hadbeen tripped


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Panel labels

Note: More warning labels are requiredadjacent to the inverter and DC disconnectat the roof location. Once APS or theutility company authorizes the connectionto the grid, a secondary digital meter wi thremote reading capability will be added tothe service panel. During a light usageday and with full sunlight, the servicepanel meter will run backwards.

APS (servering the Flagstaff Area) willrequire the owner of the system to readthis meter once a year and report the totalPV generating quantities. Now that theapplicant is in a generator capacity, a logor notebook is probably going to beneeded!


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More details


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Key remindersIf a solar panel is partially shaded vertically, then it only reduces the panel production by thepercentage of cells shaded; however, shading the top or bottom of a panel horizontally will

short out the entire panel and reduce the electricity produced.One of the leaders in authoring the Article 690, National Electric Code Bill Brooks of BrooksEngineering, LLC [[email protected]; 707-332-0761] provides an excellent seminar throughAZBO. Excellent source of information.[http://www.solarenergy.org/workshops/solarindustry.html]Factoid: silicon or sand is the 2 nd most abundant material on the plant!When sunlight hits the ground, each square meter (approximately 10 square feet) of earth iscapable of producing 1000 watts. The basic formula is P=V*I (v=voltage and I = intensity orcurrent).Factoid: Temperature affect voltage, so voltage increases as temperature drops and isreduced when it gets hotter. Light affect current (intensity) or the amperes.Photo voltaic systems are somewhere between 10-15% efficient (without intensifiers). Solar

water heaters (thermal systems) are 40% or greater in efficiency.One silicon solar cell produces 0.5 volts. Electricity is produced when light knocks looseelectrons from silicon atoms. The freed electrons have extra energy or voltage. Cells never

run out of electrons.


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Common Problem AreasInsufficient conductor ampacity and insulation wiring is undersizedfor the load or the insulation type is not designed for hot locations.Roof tops often exceed 90 (F) degrees.Excessive voltage drop DC (direct current) loss because of longdistances to inverter.Unsafe wiring methods inexperience by the installerLack of or improper placement of over current protection anddisconnect devicesUse of unlisted or improper application of listed equipment (i.e., AC inDC use)

Lack of or improve equipment or system groundingUnsafe installation and use of batteriesImproper mounting and connection of equipment and racks


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Completed panel array

From the street side, this roof top solar panel generating system (5.61 Kwh) awaits the Cityinspection and green tag. Once that it completed, APS is scheduled to replace the service panelmeter with a bi-direction digital meter and approve the installation for operation. Then during thepeak months, the owner hopes to run the meter backwards as it generates more than used.


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Now what everyone wants!!!

Click the picture on the left to see the meter in normal operation. Click thepicture on the right to see what happens when the inverter kicks in and you areon solar power!!!


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Commercial Applications

Key considerations for Commercial jobs is a factor of sizing. Per the NEC, systems over 600 amps require adesign professional (Arizona State Registrant) to beinvolved.

The following example was for a new commercial grocerystore; New Frontiers and the system is rather large at

35 Kwh production


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New Frontiers 35 Kwh system(May 2008)

This system usesmultipleconverters andseveral largearrays of solarmodules (panels)to produce thedesiredelectricity


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New Frontiers array over shedroof (May 2008)


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New Frontiers roof mountedportion

The rackingsystem for thisinstallation islaid flat on thebuilt up roofingsystem. Caremust be takento interconnectthe panelsbefore they arelowered and

connected.Obviously,maintenance toan interior panelis morecomplex.


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New Frontiers another view

The electricalboxes (at ends of panel arrays) andconduit withconductors for theconnections tothe inverterbank(s) aresnaked through aroof mounted and

protected conduit(shown in theforeground).


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Photo voltaic meter and APS dis-connect switching box

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