Camus Hydronics MFH060 Installation, Operation And Service Manual page 27

Mode 3: Dedicated Domestic Hot Water Operation
This mode is designed for domestic hot water. A DHW sensor must be inserted into a temperature
immersion well within the DHW tank to function properly. The BTC 1 modulates the boiler based on the
boiler inlet sensor to maintain a tank temperature at the DHW sensor.
An internal heat demand is generated when the DHW sensor drops ½ (half) of the tank differential setting
below the desired DHW tank temperature. Dem 1 is lit on the LCD screen.
The BTC 1 then changes the modulation output to the START modulation setting and closes the Stage
contact (pins 15 & 16) to proceed to trial for ignition. The burner remains at minimum modulation until the
flame is proved and then modulating output changes the boiler output to maintain the programmed boiler
target temperature at the boiler inlet sensor. Once the DHW tank reaches ½ of the tank differential above
the TANK TARGET setting, the internal demand is removed and the boiler burner is shut off. The pump
circulates until the PUMP DELAY timer expires.
The TANK TARGET setting is used to set the desired DHW tank setpoint. The set-point for inlet water is
pre-set to 130° F and can be adjusted, the auto re-s et 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 210° F.
Figure 16: Mode 3 Piping & Electrical Layout
Mode 4: Outdoor Reset using Boiler Inlet Sensor
This mode is designed for hydronic heating. Once a heat demand is present, the BTC 1 turns on the
appliance pump and modulates the boiler to maintain the calculated outdoor reset target at the boiler inlet
sensor. Outdoor reset calculates the boiler target temperature based on the outdoor air temperature and
reset ratio.
A heat demand is generated when a voltage between 24VAC and 120VAC is applied across CD
(common demand) and Ht D (heat demand). Once voltage is applied, the BTC 1 turns on the Dem 1
segment in the display. If warm weather shut down (WWSD) is activated, the WWSD segment is lit.
If WWSD is not activated and the inlet sensor is ½ (half) of the differential below the calculated BOIL
TARGET, the BTC 1 then changes the modulation output to the START modulation setting and closes the
Stage contacts (pins 15 & 16) to proceed to trial for ignition. The burner remains at minimum modulation
until the flame is proved and then modulating output changes the boiler output to maintain the calculated
boiler target temperature at the inlet sensor. If the inlet sensor reaches ½ (half) of the differential above
the BOIL TARGET, the appliance is shut off. The boiler pump continues to circulate until the PUMP
DELAY timer expires.
The water temperature is controlled based on a calculated boiler target temperature. The boiler start
o
(BOIL START) temperature is pre-set to 70 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.
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