Camus Hydronics MFH060 Installation, Operation And Service Manual page 26

Mode 2: Constant Temperature Control at System Sensor
This mode is designed for hydronic heating. Once a heat demand is present, the BTC 1 modulates the
boiler burner to maintain the boiler target at the system sensor. A heat demand is generated when 24VAC
is applied across CD (common demand) and Ht D (heat demand). Dem 1 on the LCD display is lit.
If the system sensor is ½ (half) of the differential below the BOIL TARGET, the BTC 1 then changes the
proportional modulation output to the START modulation setting, the Stage contact (pins 15 & 16) closes
to proceed to trial for ignition. The burner remains at minimum modulation until the flame is proved and
then the modulating output changes the boiler burner output to maintain the programmed boiler target
temperature at the system sensor. If the system sensor reaches ½ (half) of the differential above BOIL
TARGET setting, the burner shuts off. Once the external heat demand is removed, the BTC 1 turns off
the appliance and operates the boiler pump based on the PUMP DELAY setting. In this case, it is
imperative that the system pump operates continuously in order to provide constant circulation past the
system sensor.
The water temperature is controlled based on a fixed setpoint (BOIL TARGET).The setpoint for inlet water
o
is pre-set to 120 F and the auto re-set limit is set to 210° F and is fixed. In addition to the auto reset limit
the factory installs a manual re-set limit set to 250° F.
Figure 14: Mode 1 Piping & Electrical Layout
Figure 15: Mode 2 Piping & Electrical Layout
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