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BOILER PUMP OPERATION (
The boiler pump contact operates when:
• A heat demand is present and parallel piping (Mode 1, 3, 5) is used. Parallel piping requires the boiler pump to
operate even while the burner is off in order to provide heat to the system.
• While the burner is firing and primary / secondary piping (Mode 2, 4, 6) is used. Primary / secondary piping reduces
standby losses by isolating the boiler from the system while the burner is off.
• During external direct drive operation (mode 7), the boiler pump contact closes whenever there is a heat demand.
• After the burner shuts off the boiler pump remains on to purge heat from the boiler to the system.
• During a DHW demand the boiler pump contact is closed unless DHW priority is selected. During DHW priority, the
boiler pump contact is off.
BOILER PUMP PURGE (
After the burner is shut off, the control continues to operate the boiler pump for a period of time. The length of time that the
boiler pump continues to run is based on the Pump DLY setting. Once the burner turns off, the control keeps the boiler pump
running for the time selected. This setting allows purging of any excess heat out of the boiler after the boiler is shut off. This
also helps to prevent the water in the boiler from flashing into steam after the boiler is shut off.
When Pump DLY is set to OFF, there is no purging. When Pump DLY is set to ON, the pump runs continuously. When on is
selected and the control is configured for outdoor reset, the pump continues to run even during Warm Weather Shut Down.
EXERCISING
If the boiler pump has not operated at least once every 70 hours, the control turns on the output for 10 seconds. This mini-
mizes the possibility of the pump seizing during a long period of inactivity.
Section B: Setpoint Operation
When either mode 1 or 2 is selected, the water temperature is controlled based on a fixed setpoint. The setpoint
temperature is set using the BOIL TARGET item in the Adjust menu.
HEAT DEMAND (Dem 1)
A heat demand is required whenever heat is required for the setpoint load. A heat demand is generated when a voltage
between 24 and 120 V (ac) is applied across the CD (common demand) and the Ht D (heat demand). Once voltage is
applied, the control turns on the Dem 1 segment in the display. The control closes the pump contacts, which starts the
boiler pump and the control turns on the boiler pump segment in the display.
If the operating sensor is 1/2 of the differential below the BOIL TARGET, the control then closes the Stage 1 contact. The
boiler target temperature is set using the BOIL TARGET item in the Adjust menu. If the operating sensor reaches 1/2 of
the differential above the BOIL TARGET setting, the boiler burner is shut off. The pump contact remains closed until the
heat demand is removed and Pump DLY setting expires.
8
Model SF-10 Control Instructions Manual
)
DLY)
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