How do I size a generator?

When sizing a generator it is important to take into consideration the running loads and the starting currents. For example, the running current of a 3 phase 10 HP induction motor will be approximately 13 Amps, however the starting current will be between 3 and 9 times the running current i.e. 39 to 117 Amps.

What are the requirements for a generator set?

They also must satisfy high “magnetizing current” draws (kVAR), or transient conditions from electrical equipment. Normally, a generator set is furnished with a generator which matches the engine output capability.

What are the NFPA guidelines for installing a generator?

Based on this testing and the requirements of NFPA 37, Sec 4.1.4, the guidelines for installation of the generators listed above are changed to 18 in (457 mm) from the back side of the generator to a stationary wall or building (C).

How deep should a generator be?

Prepare a rectangular area approximately 5 in (127 mm) deep (A) and approximately 6 in (152 mm) longer and wider (B) than the footprint of the generator. Verify the surface where the generator will be mounted is compacted, leveled, and will not erode over time. A concrete pad can be poured if desired or required. Figure 3-3.

How are engine and generator capacities considered in a generator set?

Capabilities of both engine and generator are considered individually and collectively when selecting generator sets. Engines produce brake horsepower (or kilowatts) while controlling speed or frequency.

How to choose a generator set?

Always investigate to ensure the selected generator set will meet application requirements. The way an engine is configured can affect the size of genset needed. The load acceptance behavior of an engine also depends on the type of air supply to the combustion system. Maximum engine power may be airflow restricted.