Sizing Guide for Water Heater

7/31/2019 Sizing Guide for Water Heater

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Engineering Data Document 5067G

Sizing Increments = No. of Units x TF x FR x CWUnit Type Factor (TF)

Unit Type Factor

1 Bedroom Apt. 1.02 Bedroom Apt. 1.5Hotel/Motel Room 1.3Coin-Op. Washing Machine 0.5

Shower Flow Rate Factor (FR)

Flow Rate Factor

2 gpm 0.673 gpm 1.04 gpm 1.35 gpm 1.7

Inlet Cold Water Temp. Factor (CW)

Water Temp. Factor40oF 1.050oF 0.960oF 0.870oF 0.75

This Sizing Guide provides asimple method of accuratelydetermining the correct heater/storage tank combination forapartment and condominiumcomplexes, hotels and motels. Byproviding a variety of heater andtank combinations, the Sizing

Guide allows the system designerto optimally utilize existingequipment and boiler room floorspace. Sizing is based on servicewater heating recommendations ofthe American Society of Heating,Refrigeration and Air ConditioningEngineers.

Note: This is a guide and thesystem designer should considerall load demands and heat lossescarefully.

Useful sizing equation: BoilerOutput (BTU/hr) = 500 x GPM flowthrough boiler x temperature rise(F) through boiler.

Selecting the appropriate waterheater/storage tank combination isa three-step procedure:

1. Use the table on this page todetermine the total number ofsizing increments in theinstallation.

For sizing information onservice hot water forcommercial laundry seedocument number 5010,Laundromats and CommercialLaundries. Calculate thosedemands separately, add toany other domestic hot waterrequirements in the facility.

2. The graphs on pages 3 and 4provide various combinationsavailable based on theinformation from Step 1. Graphs1, 2 and 3 are for interior andexterior installations.

3. The system designer cancombine the information from

Steps 1 and 2 with theperformance and dimensionaldata from documents 2044,2045 and 2046 to select theoptimal water heater and storagetank to complete the installation.

Sizing Guide for

Domestic Volume Water Heaters

Sizes 175,000 - 5,000,000 BTU/hFor Apartment and Condominium Complexes, Hotels and Motels


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Apartments Examples

NOTE: Any combination of water heater and storage tank can be used as long as they cross the sizingunit line. Whenever the combination falls on the size line, the larger unit should be installed.

New 66 Unit Apartment Complex

44 1 Bedroom 1 Bath Units


5 Coin-Operated Machines

3 GPM Shower Heads

50F Inlet Cold Water Temperature

Graph 2 provides thefollowing possiblecombinations of water

heater and storage tank(Specify Model IWInstantaneous wheneverthe system does notinclude a storage tank).

Total Sizing Increments = [Number of Apartment Units x TF] x

FR x CW

= [(44 x 1) + (22 x 1.5) + (5 x 0.5)]

x 1 x 0.9

= 71.55

Size 1010 No TankSize 715 120 gal. TankSize 600 230 gal. Tank

Size 500 380 gal. Tank

If the existing tank needsto be replaced, as well as

the water heater, thefollowing combinationscould be used:

Existing 100 Unit Apartment Complex

(with a 120 gallon storage tank)



4 GPM Shower Heads


Water heater to be placed outdoors.

Size 1200 380 gal. TankSize 1010 535 gal. Tank


Total Sizing Increments = [Number of Apartment

Units x TF] x FR x CW

= [(66 x 1) + (34 x 1.5)] x 1.3 x 0.9

= 136.9

Existing Hotel with 1000 gallon Storage Tank

145 Hotel Rooms4 GPM Shower Heads


Total Sizing Increments = Number of Hotel Units x TF x FR x CW

= 145 Hotel Units x 1.3 x 1.3 x 1

= 245

Graph 3 shows that asize 2000 heater utilizingthe existing 1000 gallon

storage tank can beinstalled.

New Hotel

315 Hotel Rooms4 GPM Shower Heads


Graph 3 provides thefollowing possiblecombinations of water

heater and storage tank:

Hotel Examples

Size 5000 800 gal. TankSize 4500 1500 gal. Tank


Total Sizing Increments = Number of Hotel Units x

TF x FR x CW

= 315 Hotel Units x 1.3 x 1.3 x 0.9

= 479.1


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STORAGE TANK CAPACITY (IN GALLONS)

1825

1670

1430

1200

1010

850

715

600

500

500 100 150 200 250 300 3

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SIZING INCREMENTS

Graph 2SIZING INCREMENTS 45 - 300

INDOOR

AND

OUTDOOR

SIZES

200015001000800650535230

119 380IW*

*(IW) Instantaneous heaters with no tank

SIZING INCREMENTS


50 10 15 20 25 30 35 40 4

230

119

82


INDOOR

AND

OUTDOOR

SIZE

S500

400

325

250

175


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MODEL

5000 I

200150 250 300 350 400 450 500 550 600

15001000800

535 2000

SIZING INCREMENTS

INDOOR

AND

OUTDOOR

SIZE

S


4500 I4500 E

4050 I4000 E

3500 I

3600 E

3050 I3200 E

2450 I2800 E

2000 I2200 E

IW*

I = Indoor E = Outdoor*(IW) Instantaneous heaters with no tank

800.900.9276 Fax 800.559.1583 (Customer Service, Service Advisors)

20 Industrial Way, Rochester, NH 03867 603.335.6300 Fax 603.335.3355 (Applications Engineering)

1869 Sismet Road, Mississauga, Ontario, Canada L4W 1W8 905.238.0100 Fax 905.366.0130

www.Laars.com Litho in U.S.A. Laars Heating Systems 0810 Document 5067G

Sizing Guide for Water Heater

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