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BOILER CONTROL: INTERNAL WIRING & OPERATION
A. CONTROL OVERVIEW
The Series PFC™ boiler control is one of the primary
safety devices for the boiler. It controls:
• Ignition sequence
• Temperature Limits
• Circulators
• Gas Flow
• Setpoints
• Domestic Hot Water Priority
• Fan Speed
• LWCO
B. AVAILABLE CENTRAL HEAT MODES
Table 8.1: Series PFC™ Central Heat Modes
Central
Heating
Mode
Mode Description
Mode Operation
0
Fixed Setpoint
– Demand initiated by T/TT closure.
– User selected fixed setpoint.
– When demand is present, the boiler targets CH setpoint and
operates based on the Supply temperature hysteresis.
– Not for space heating. Used for combustion testing.
1
Outdoor reset with
Thermostat
– Demand initiated by T/TT closure.
– Setpoint is calculated based on the Outdoor temperature and CH
demand period to improve fuel usage and boiler efficiency.
– Setpoint Boost function for long CH demand periods.
– When demand is present, the boiler targets calculated CH setpoint
and operates based on the Supply temperature hysteresis.
– When the Boost Function is active and CH demand is not present,
CH setpoint decreases back to the calculated setpoint.
2
Outdoor reset with
Permanent Demand
– Demand initiated by control logic. Always present.
– Setpoint is calculated based on the Outdoor temperature to improve
fuel usage and boiler efficiency.
– Boiler targets calculated CH setpoint and operates based on the
Supply temperature hysteresis.
– When CH demand is not present, calculated setpoint decreases gradually.
3
Fixed Setpoint with
Permanent Demand
– Demand initiated by control logic. Always present.
– User selected fixed setpoint.
– Boiler maintains CH setpoint and operates based on Supply
temperature hysteresis.
– Not for space heating.
4
Analog Input Control of
Setpoint
– Demand initiated by an analog input of 1.5 Vdc or higher.
– Demand will be removed when the voltage drops below 1 Vdc.
– Boiler setpoint is controlled by an analog input signal provided by a
Building Management System or controller.
– Setpoint modulation occurs between 2 and 9 V.
– Setpoint range is 60°F (15.5°C) to 185°F (85°C).
5
Analog Input Control of
Power Output
– Demand initiated by an analog input of 1.5 Vdc or higher.
– Demand will be removed when the voltage drops below 1 Vdc.
– Boiler fan speed (power output) is controlled by an analog input
signal provided by a Building Management System (BMS) or
controller.
*While accessible via the Installer menu, CH Modes 4 and 5 are not functional with the Series PBC™ boiler.
NOTE: Hysteresis is similar to differenctial.
8. BOILER CONTROL: INTERNAL
WIRING & OPERATION
