Camus Hydronics MFH060 Installation, Operation And Service Manual page 30

Mode 7: External Target Temperature using System Temperature Sensor
The external input signal can be provided from a BMS, EMS or a tekmar tN4 System Control. The
external input signal creates an internal demand and changes the boiler target according to a linear scale.
The control modulates the boiler to maintain the boiler target at the outlet sensor.
An internal heat demand is generated when an analog positive 2-10VDC signal is applied to the +V input
and a negative DC signal is applied to the Com/- input.
Table 7 shows the relationship between various external signals to the boiler target temperature. A 4-
20mA signal can be converted to a 2-10VDC signal by installing a 500 resistor on the external input
signal device's terminal.
If the system sensor is ½ (half) of the differential below the Boiler Target, the BTC 1 then changes the
proportional modulation output to the START modulation setting, then 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 the modulating output changes the boiler burner out to maintain the programmed boiler target
temperature at the system sensor. If the inlet sensor reaches ½ (half) of the differential above Boiler
Target, 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.
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The auto reset limit is set to 210 F and is fixed. In addition to the auto reset limit, Camus installs a manual
o
reset limit set to 250 F.
Figure 20: Mode 7 Piping & Electrical Layout
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