Where pump sizes are relatively small (up to 7.5 horsepower), the generator shall be sized to start and run both pumps and serve all other loads at the station. When the pump sizes are 10 horsepower or larger, the generator shall be sized to start and run one of the pumps and serve all other loads at the station. The necessary interlocks shall be provided to prevent the lag pump from starting and running when the station is on standby generator power. The lag pump shall be capable of starting and running, however, if the lead pump fails to start. The transient voltage dip shall not exceed 20 percent.

Generator sizing calculations shall be furnished for review by the WSSC. (Design Guideline DG-08 § 18.1, dated August 2006)