Koolaire KDT0300A Technician's Handbook page 99

FREEZE CYCLE
The HPR system is not used during the freeze cycle.
The HPR solenoid is closed (de-energized), preventing
refrigerant flow into the HPR valve.
HARVEST CYCLE
During the harvest cycle, the check valve in the discharge
line prevents refrigerant in the remote condenser and
receiver from back feeding into the evaporator and
condensing to liquid.
The HPR solenoid is opened (energized) during the harvest
cycle, allowing refrigerant gas from the top of the receiver
to flow into the HPR valve. The HPR valve modulates open
and closed, raising the suction pressure high enough
to sustain heat for the harvest cycle, without allowing
refrigerant to condense to liquid in the evaporator.
In general, harvest cycle suction pressure rises, then
stabilize. Exact pressures vary from model to model. Refer
to cycle time/24 hour ice production and operational
pressure charts.
HPR DIAGNOSTICS
Steps 1 through 5 can be quickly verified without attaching
a manifold gauge set or thermometer.
All questions must have a yes answer to continue the
diagnostic procedure.
1. Liquid line warm?
(Body temperature is normal)
If liquid line is cooler than body temperature, refer to
head pressure control valve diagnostics.
2. Ice fill pattern normal?
Refer to "Ice Formation Pattern" if ice fill is not
normal.
Part Number STH063 9/17 99