SINGLE AND MULTIPLE BOILER INSTALLATIONS:

If one boiler is being fed, one pump may be used, actuated by the level control mounted on the boiler. A duplex feed unit may also be used with each of the two pumps sized to independently feed the boiler. For the duplex unit, a "Lead- Lag" switch may be used to manually select the lead pump and, if desired, to permit two-pump simultaneous operation when necessary, or an electric alternator can automatically alternate the pumps and provide simultaneous emergency operation.
When feeding two boilers with two pumps, each pump can be sized to feed one of the boilers, being actuated by the water level control on its assigned boiler. A transfer switch may be used with this arrangement, along with necessary cross-over piping, to manually change the boiler-pump relationship. A third pump may be used as standby for either boiler and can be operated manually, or automatically with electric valves, in emergencies.
When feeding two, three or more boilers, two pumps can be used, each individually sized to handle the combined load of all boilers. The second pump acts as a standby and provides double capacity in emergencies. Both pumps feed a common header from which feed lines branch off to each boiler. The level control on a boiler operates the corresponding electric valve in its branch feed line, and an end switch in the valve turns on the pump. A "Lead-Lag" switch or automatic alternator can be supplied for these arrangements. A third pump can be used for standby service.