Setpoints and related data
The setpoints and related data include the following items:
- Number of cooling stages installed (#ClgStgs)
- Compressor stage command (Ci for i=1 to 4)
- High pressure limit (HPSi for i=1 to 4)
- High pressure lockout (HPSi-LO for i=1 to 4)
- Reset lockouts (ResetLO)
Inputs
The input for the high pressure switch is contact closure from the appropriate refrigerant circuit high pressure switch (HPS1, HPS2, HPS3, HPS4).
Outputs
The output for the high pressure switch is the output relay for the appropriate refrigerant circuit (C1, C2, C3, C4).
Operation
The control reads this input only when it has the compressor relay turned on. If the high pressure switch opens for more than two line cycles, the UCB turns off the compressor relay and starts the ASCD. After the ASCD times out, the UCB turns on the compressor relay as long as there is still a call for cooling.
The UCB logs the first incident and tracks the runtime. If the high pressure switch opens three times within 2 hours of runtime, it locks out the compressor and displays an alarm on the LCD. While the UCB has all compressors locked out, it turns off the condenser fan.
Any time a lockout occurs and the call for cooling goes away, this resets the lockout.
Any high or low pressure switch or freezestat error during minimum runtime terminates the minimum runtime.