21 750-265
Fig. 6. Burner demand priority control.
CH Loop Demand and Rate
The CH (Central Heating) Demand and Rate source
compares a selected input sensor to a setpoint.
Burner demand will exist if the sensor temperature falls below
the setpoint minus a hysteresis value. Once the burner
demand signal is on, it remains on until the sensor
temperature is above the setpoint plus a hysteresis value, or
until the other selected demand source input (e.g., Stat,
Remote Stat) if any, turns off.
Pump demand may be driven by the selected demand source
input (Stat input, a remote stat, or by the sensor alone).
A Proportional-Integral-Differential (PID) controller operates to
generate the demand source’s requested modulation rate.
The Central Heating function is implemented as shown in
Fig. 7.
DETERMINE IF DHW DEMAND SHOULD IGNORE AN ANTI SHOR T CYCLE (ASC) DELAY...
M24972
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