Gerry 2015 MacBookColor of Water

Choosing the Right BoilerQuestions to be asked before choosing the boiler:

Good for cast iron:What is the heat load of the building?

What is the heat capacity of the connected radiation?

Is it more or less than than the building heat load?

What is the radiation made up of: baseboard, cast iron radiators, air handlers?

Is it a steam or hot water boiler?

Good for modcon:

Depends…

Proper Boiler SizingEvery contractor worries about undersizing, but few give a thought to oversizing…

Is bigger always better?

If the boiler’s too small, my customer will be cold and unhappy

at the worst possible time. The boiler will run without stopping.

If the boiler’s too big, what’s the worst that can happen?

Nobody ever complains they are too warm, right?

Boiler Short-Cycling

Higher fuel usage

Boiler stops working at the worst possible time

Reduced component lifetime/Boiler needs parts all the time

Boiler fails after a few years and must be replaced

Cast Iron vs ModCon BoilersWhich one is more likely to short-cycle? ModCon boilers are smaller and can down-fire to a fraction of the full input. Shouldn’t that help? Maybe. Or not…

+ Cast iron boilers have (6x) more water and more mass to absorb heat at start up.

- They have only one level of heat input – full.+ They cool down more slowly.

Causes of Boiler Short-Cycling

Boiler btu input is much higher than the heat loss of the building.

Water flow through the boiler is restricted by pipe design, pipe

size or lack of circulator capacity.

Many small heating zones

+ ModCon boilers control btu input from high-fire through low-fire as the water

temperature gets near the target.

- They heat up and cool down quickly.

Radiators & Other Heat EmittersModern hydronic systems can have many types of radiation to provide heat throughout

a structure, including baseboard, convectors, radiators, hydro air coils, radiant, etc.

Heat emitters receive heat from the hot water circulating through the piping and deliver heat to the areas where they are installed. 150-180˚

150-180˚

120-160˚

DOs AND DON’Ts OF SIZING REPLACEMENT BOILERS

For Steam

Do size according to the installed radiation load. Be sure to make appropriate allowance for additional piping and pick-up.

Don’t size based on a heat loss.

Use the existing boiler size and firing rate as a guide and/or cross-reference only.

For Hot Water

Do size based on a heat loss if the system is copper baseboard. OK to size a copper baseboard system based on the lineal footage of installed radiation.

Do size according to the installed radiation load if the system is cast iron radiation. Be sure to make appropriate allowances for additional piping and pick-up.

Use the existing boiler size and firing rate as a guide and/or cross-reference only.

TECHNICAL TIDBITS

Piping and pick-up factors for I = B = R Rated Boilers: Hot Water = 1.15 Steam = 1.33

1 Boiler Horsepower = 33,475 BTUH

1 Lb. Steam (212°F) = 970.3 BTU

1 Sq. Ft. of Steam = 240 BTUH

1 Sq. Ft. of Water = See Table Below

HEAT EMISSION BASED ON ROOM TEMPERATURE OF 70°F

Avg water temp in radiation… 150 160 170 180 190 200 210 215 Heat emission BTUH/sq. ft… 110 130 150 170 190 210 230 240

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Room Name§ Feet of Copper

Baseboard ElementNumber of

CI Radiators# of Tubes or Columns

Number of Sections

Cast Iron Height

Cast Iron Width

Feet of CI Baseboard

EDR*/Section or /Foot from Chart Total

12345678910111213141516171819202122232425

= Total Feet of Copper BB Element TOTAL EDR == Element x 600 BTUH§ (@180˚) EDR x 150 BTUH† (@170˚) =

§Water temperature other than 170˚ see capacity chart † For water temperature other than 170˚, see EDR Output Chart

*EDR = Square feet of Equivalent Direct Radiation

(Enter #T for Tubes or #C for Columns)

RadiationMeasuringSheet

Room by Room Calculation

Block Calculation

Peerless Heat Load Quick Enter Sheet.xls

f Peerless Heat Load Quick Enter SheetDATE

JOB NAME

WHOLESALER __________________________ CONTRACTOR ft ft ft ft sq ft sq ft sq ft sq ft sq ft sq ft ft sq ft sq ft sq ft

# Room Name Room Room Exp. Ceil North East / South Skylight SE / SW Floor Floor Exposed Standard Patio Loss GainLength Width Wall Height Window West Area Edge Ceiling Doors Doors BTUH BTUH

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

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Construction & Insulation Factors ("R" Value / Inches of Insulation) {0"=R3, 2"=R7, 3.5"=R12, 6"=R20, 9"=R30, 12"=R40}Circle below all factors that apply: Glazing

** Exposed Wall 0" / 2" / 3.5" / 6" ** Glass Door sgl/dbl **Cold Floor Perimeter 1" / 2" Heating Temp. ( O F Outside) ** ** Ceiling 0" / 3.5" / 6" / 9" / 12" ** Skylight sgl/dbl ** Standard Doors Y / N Cooling Temp. ( O F Outside) **

** Cold Floor Area 0" / 3.5" / 6" / 9" / 12" ** Glass sgl/dbl _______ Air Change / Hour .5 / 1.0

All Areas with ** are needed in order to complete load calculation

PEERLESS® BOILER – Basic Hydronics

Water enters through the eye.Vanes “slap” the water – adding velocity.Discharge side turns velocity to pressure.

It uses centrifugal force.

How Do Circulators Work?

The wider the impeller, the more flow.The larger the diameter or pitch, the more velocity & pressure.Increase the speed - more flow and pressure.

It’s a “circulator” not just a pump.It creates pressure differential.

Pressure differential creates flow.Enough pressure differential

= enough flow.

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PEERLESS® BOILER – Basic Hydronics

Sizing Circulators – What is Feet of Head?

1 PSI = 2.31’ head pressure

12 PSI 2.31’ = 27.72’

Keep radiation pressurized

on upper levels

Static head (from PRV): Pressure needed to fill system to highest point, typically 12 PSIFriction head: Pressure needed to overcome friction loss in piping

Pump head: Amount of pressure the pump can produce (PSI 2.31)

vs

Atmospheric Pressure

100’

43.3 psi

pos pr

neg pr

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Number'of'Baths

Number'of'Bedrooms

Wired'for'Priority

Wired'for'Non5Priority

2 5,100 10,4001'5'1½

3 5,100 10,400

2 5,100 10,400

3 6,100 13,0002'5'2½

4 7,000 14,300

5 10,400 20,500

3 7,000 14,300

4 8,200 17,3003'5'3½

5 10,400 20,500

6 11,000 21,500

Add'to'Heat'Load

Sizing'Additional'Boiler'Load'for'DHW

PEERLESS® BOILER – Basic Hydronics

Water flow carries the heat from the boiler to the radiation. If we know how many btus of heat are needed, we can convert them into gpm using the universal hydronics formula.

gpm = btuh/(∆T x 500)

Sizing Circulators - Flow Needed

Formula

Btu (British Thermal Unit) = heat required to raise 1 pound of water by 1 degree Fahrenheit

Btuh = btus created or used per hour

∆T = change in temperature

1 gallon of water = 8.31 pounds

60 minutes (as in gpm) = 1 hour (as in btuh)

Convert pounds and minutes to gallons and hours8.31 x 60 = 498.6 (round to 500)

BTUH / ∆T x 500

Example

180˚ - 160˚ = 20˚ ∆T (typical for heating systems)

Using formula:

63,000/(20 x 500) = ? gpm

63,000/10,000 = 6.3 gpm

To calculate flow for a zone circulator, calculate how many mbh the zone

requires and divide by 10,000.

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PEERLESS® BOILER – Basic Hydronics

For residential cast iron boilers with zone valves, measure the length of only the longest run.The circulator has to overcome the resistance in that run. The shorter runs are easier.

In our example all the runs have the same length.

Sizing Circulators – Feet of Head Restriction

To convert measured length of longest run to feet of head:

Multiply measured length x 1.5 (factor to account for all the fittings)

Multiply that number x .04

Example:90 ft x 1.5 = 135

135 x .04 = 5.4

Or

90 x .06 = 5.4

Measured length =

90 ft

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PEERLESS® BOILER – Basic Hydronics

Our sample heat loss was 63 mbh, which would make the MI85-04 a good choice.

6.7 gpm is required. Our longest run of 90 feet requires 5.4 feet of head.

The Taco pump curves show that a model 007 has more than enough capacity.

Sizing Circulators –Cast Iron Boiler Example

X

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PEERLESS® BOILER – Basic Hydronics

Sizing Circulators – Modcon Boiler Example

The PF210 requires more flow and head capacity than standard Taco 00 series provides even with a 25˚ ∆T.

Taco model 2420 is a good match for the PF210.

X

XX

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PEERLESS® BOILER – Basic Hydronics

Maximum Btus for Pipe SizeUsing 20˚ ∆T from the universal hydronics formula, the

two tables below show the maximum water floe and maximum btu capacity for each size steel or copper pipe.

Example for boiler piping on PF210:

PF210 heating capacity = 195 mbh = 19.5 gpm

From the tables – 1¼” pipe is too small at 16 gpm max

1½” pipe has enough capacity at 25 gpm max

The boiler loop on the PF210 should be piped with 1½"

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