ClimateWorx M52 - Reheat, Humidifier, and PID

Advanced M52 Microprocessor User's Guide
ADVANCED M52UMCT2019 COLOR
8
The Dehum. Solenoid (DSV) closes off refrigerant flow to part of the evaporator coil. This
causes a drop in suction pressure and a lower coil surface temperature over a portion of the coil.
The coil begins to remove more moisture as a result. The air is partially reheated, as the air
through the inactive part of the evaporator is unconditioned. This creates an overall drop in the
sensible heat ratio (Rapid Dehumidification)
During dehumidification demand, some sensible cooling takes place. Under very low load
conditions, the sensible cooling affect maybe greater than the combined offsetting effect of the
heat load plus the available reheat capacity, which may cause a drop in room temperature. If
temp continues to drop and is less than (set point MINUS (temp dead band DIVIDED by 2)
MINUS heating proportional band) the compressors will stop overriding the demand for
Dehum. The temperature must return to set point before another cycle of dehumidification
starts.
ie: Low limit cutout =Set point – (temp deadband 2) – heating propband
Compressor stops when:
 Loss of demand
Compressor contactor opens
 Low pressure condition
Compressor stops when LP SW. opens. (Automatic reset) compressor contactor opens.
 Short cycling alarm (Low Pressure)
After three consecutive low-pressure alarms in 60 minutes, compressor contactor opens.
Alarm must be acknowledged and cleared before Compressor will start or cycle power.
 High pressure condition
Compressor stops when HP Switch opens. (Manual reset)
Compressor contactor opens. Compressor will not start until HP Switch is manually reset
and Alarm is acknowledged and cleared.
 Thermal protection opens (automatic reset)
Line voltage cut-outs on all compressors except Specter compressor where the compressor
module causes a Compressor Overload alarm and stops the compressor through the
microprocessor. Compressor module resets after 30 minutes.
 Low limit temperature
If return air temperature continues to drop and is less than (setpoint MINUS (temp dead
band DIVIDED by 2) MINUS heating proportional band) the compressors will stop
overriding the demand for Dehum.
Note: Anytime the compressor contactor opens the comp. elapse timer keeps compressor off
for 3 minutes (adjustable). There is also a compressor minimum runtime of 3 minutes
(adjustable) which will prevent the compressor from being turned off by the control. The
compressor can stop during this time through high or low pressure or by cycling the power.
Dual Cooling Units:
Dual cooled units operate on DX as described above in DX Cooling Demand and DX
Dehumidification Demand. In DX mode the chilled water valve is closed. When a remote
signal contact input closes on Compressor Disable Terminal 31 and 32 the compressors will
stop and the unit will operate as described in Chilled Water above.
Free Cooling Units:
Free cooling units operate on DX as described above in DX Cooling Demand and DX
Dehumidification Demand when the glycol loop or outside air temperature is above 7.2C, (45F
adjustable). The modulating glycol valve or output signal for outside air dampers begins to open when
the difference between the return air temperature (Temp Return Air) and the entering glycol
temperature or outside air temperature (Temp EGT/ Ambient) is greater than 3C, (6F adjustable).
The unit will operate in Free Cooling as long as the cooling demand remains in the 0-50% range.