Within this booklet, you will find electrical load information, plus an outline of generator surge capability, fuel pipe
Sizing Guide
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GENERATORS
Generator Sizing Guide General Information
Important Notice This booklet is designed to familiarize estimators and installers with proper sizing guidelines for residential and commercial generators. The information is not comprehensive, nor does it replace or supercede any material contained in any of the written documents shipped with the equipment. This booklet should only be used in conjunction with the Owner’s Manual, Installation Manual and other technical documents shipped with each product. Always read all accompanying documentation carefully before attempting to install any generator, transfer switch or related equipment. How to Use this Booklet Within this booklet, you will find electrical load information, plus an outline of generator surge capability, fuel pipe sizing, liquid propane tank sizing, and UPS / generator compatibility. The final pages are perforated for easy removal and can be photocopied to create additional Onsite Estimating Sheets for use with individual jobs. Safety Information Proper sizing of the generator is crucial to the success of any installation and requires a good working knowledge of electricity and its characteristics, as well as the varying requirements of the electrical equipment comprising the load. When analyzing the electrical load, consult the manufacturer’s nameplate on each major appliance or piece of equipment
to determine its starting and running requirements in terms of watts, amps and voltage. When choosing the generator output for commercial or industrial applications, select a rating that is approximately 25% higher than the peak load (for example, if the load is about 40 kilowatts, select a 50 kW genset). A higher rated generator will operate comfortably at approximately 80% of its full capacity and will provide a margin of flexibility if the load increases in the future. For safety reasons, Siemens recommends that the backup power system be installed, serviced and repaired by a Generac Authorized Service Dealer or a competent, qualified electrician or installation technician who is familiar with applicable codes, standards and regulations. It is essential to comply with all regulations established by the Occupational Safety and Health Administration (OSHA) and strict adherence to all local, state and national codes is mandatory. Before selecting a generator, check for municipal ordinances that may dictate requirements regarding placement of the unit (setback from building and/or lot line), electrical wiring, gas piping, fuel storage (for liquid propane or diesel tanks), sound and exhaust emissions. If you have a technical question regarding sizing or installation, contact Siemens Technical Service Center toll free at 800-844-0029 during normal business hours (8 a.m. to 5 p.m. CST).
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Generator Sizing Guide Table 1 – Motor Load Reference
AC and Heat Pumps Running Load Description 1 Ton (12,000 BTU) 2 Ton (24,000 BTU) 3 Ton (36,000 BTU) 4 Ton (48,000 BTU) 5 Ton (60,000 BTU) 7.5 Ton (85,000 BTU) 10 Ton (120,000 BTU) 10 Ton (120,000 BTU) 15 Ton (180,000 BTU) 15 Ton (180,000 BTU) 20 Ton (240,000 BTU) 20 Ton (240,000 BTU) 25 Ton (300,000 BTU) 30 Ton (360,000 BTU) 30 Ton (360,000 BTU) 40 Ton (480,000 BTU) 40 Ton (480,000 BTU) 50 Ton (480,000 BTU) 50 Ton (480,000 BTU)
Hp 1 2 3 4 5 7.5 5 Hp (x2) 10 Hp 7.5 Hp (x2) 15 Hp 10 Hp (x2) 20 Hp 25 15 Hp (x2) 30 Hp 20 Hp (x2) 40 Hp 25 Hp (x2) 50 Hp
Running kW 1 2 3 4 5 7.5 10 10 15 15 20 20 25 30 30 40 40 50 50
Amps at 240V 1ø 5 10 15 20 25 37 49 49 74 74 98 n/a n/a n/a n/a n/a n/a n/a n/a
Starting Load Amps at 208V 3ø 3 7 10 13 16 24 33 33 49 49 65 65 82 98 98 131 131 163 163
Amps at 480V 3ø 1 3 4 6 7 11 14 14 21 21 28 28 35 42 42 57 57 71 71
Starting kW 3 6 9 12 15 17 15 20 17 30 20 40 50 30 60 40 80 50 100
LR Amps at 240V 1ø 25 50 75 100 125 188 125 250 188 375 250 500 625 375 750 500 1000 625 1250
LR Amps at 208V 3ø 17 33 50 67 83 125 83 167 125 250 167 333 416 250 500 333 666 416 833
LR Amps at 480V 3ø 7 14 22 29 36 54 36 72 54 108 72 144 180 108 217 144 289 180 361
General Residential Running Load Description Refrigerator, Sump Pump, Furnace, Garage Opener Freezer, Washer, Septic Grinder General 1 Hp Well and Septic Lift Pump
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Starting Load
Hp 0.5
Running kW 0.5
Amps at 120V 1ø 4.9
Amps at 240V 1ø 2.5
Starting kW 1.5
LR Amps 120V 1ø 25
LR Amps 240V 1ø 13
0.75 1 2
0.75 1 2
7.4 9.8 19.6
3.7 4.9 9.8
2.3 3 6
38 50 100
19 25 50
Generator Sizing Guide Table 2 – Non-Motor Load Reference
General Residential Running Load Description Electric heat per 1000 ft.2 Heat pump elements per 1000 ft.2 Dryer Hot tub Range oven Hot water Stove top per burner General receptacles per 1000 ft.2 Lighting per 1000 ft.2 Blow dryer Dishwasher Microwave Toasters
kW 12 7 5.5 5 5 4.5 1.5 1 0.75 1.25 1.5 1 1
Amps at 120V 1ø n/a n/a n/a n/a n/a n/a n/a 8.3 6.3 10.4 12.5 8.3 8.3
Amps at 240V 1ø 50 29 23 21 21 19 6 n/a n/a n/a n/a n/a n/a
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Generator Sizing Guide Table 3 – Surge Capability
Siemens Liquid Cooled Generators Operating at
