RT-SVD03G-EN 141
High Pressure and Low Pressure Lockout Circuits
HPC Logic
High Pressure Cutout (HPC) is similar to the LPC in that the unit may be given up to four tries to
operate. Like the LPC, the HPC provides reliability protection for compressors, but it is also used
for safety protection due to the high operating pressures that the unit may see.
Note: At no time should the HPC be removed or disabled in order to maintain unit operation.
HPC Sequence of Operation
On a call for cooling, if the HPC switch is closed, the compressor will be allowed to start. If at any
time the HPC opens, the unit will shut down immediately. After a fifteen minute period, if there is
still a call for cooling, the control logic will check to see if the switch has closed. If not, the unit is
locked out and requires a manual reset to restart the unit.
If after fifteen minutes the HPC is closed, and there is still a call for cooling, the unit will be allowed
to restart. Once again, if the HPC opens, the unit will shut down and wait fifteen minutes to validate
a restart. If the switch is closed, the unit will be allowed to restart.
If the HPC opens and closes four times during an active call for cooling, the unit will be shut down
and locked out, and will require a manual reset.
If any time during the counter routine, the call for cooling goes away, the counter will reset and the
logic sequence starts all over again.
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