Service manual

MSE Series Electric Boilers – Installation and Service Manual

Sequence of Operation

Thermostat (T1) closed - Thermostat creates a Heat Demand resulting in a boiler target based on the

outdoor reset settings. The boiler pump (Pump1) operates.

DHW Aquastat (A1) closed - DHW Aquastat creates Setpoint DHW Demand and activates external

pump relay. The external pump relay causes the following actions:

1) Power for the boiler pump (Pump1) is broken. Pump1 does not operate.

2) Power for the DHW pump (Pump2) is made. Pump2 operates.

3) Setpoint DHW Demand creates a boiler target based on the higher requirement of the

outdoor reset and reset override setting.

Figure 7 – Wiring diagram illustrating use of an External Relay to control pump operation

5.5 CONTROLLER MOUNTING

The BC-1 controller mounts on the controller mounting plate in the control chamber using a sheet metal

screw. The LCD and buttons should visible and accessible from the front of the boiler casing. To remove

the controller: 1.) remove the front casing panel, 2.) pull off the black plastic top cover of the controller, 3.)

unscrew the sheet metal screw, 4.) lift the controller slightly out of the rectangular cutout in the mounting

plate, 5.) pull off the Molex connector while simultaneously holding down the tab on the left side.

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Pump 2

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