Comply with NEMA ICS 2 and UL 508. NEMA ICS 6, Type 12. 120-V ac, using integral control power transformer. Overload relay in each phase. Switches lead pump to lag main pump and to two-pump operation.
Switches lead pump to one lag main pump and to three-pump operation.
Unit suction and discharge pressure gages. Sounds alarm when backup pumps are operating. Unit suction and discharge pressure gages. Protect flanges, pipe openings, and nozzles. Verify that each pump is free to rotate by hand and that pump for handling hot liquids is free to rotate with pump hot and cold.