Manitowoc QuietQube Series Technician's Handbook page 163

HARVEST CYCLE DIAGNOSTICS QUIETQUBE® REMOTE
CONDENSING UNIT
The head pressure control valve diverts the compressor
discharge gas to the ice machine receiver in the harvest
cycle. All refrigerant flow through the condenser in the
harvest cycle stops. Symptoms of a head pressure control
valve that will not seat 100% closed (completely bypass the
condenser) in the harvest cycle are:
• Freeze cycle suction and discharge pressure are
normal.
• The control board indicates E02 Long Harvest, a
flashing triangle alert and after pressing left arrow
Long Harvest is displayed. The failure seems to be
temperature related. Example: The ice machine may
function correctly at temperatures above 32°F but fails
at temperatures below 32°F.
• Harvest cycle suction pressure is low.
• Harvest cycle discharge pressure is normal or slightly
low.
Procedure
1. Freeze cycle operation must be normal before
diagnosing the head pressure in the harvest cycle.
(Refer to Cycle Times/24 hr Ice Production/Refrigerant
Pressure Chart)
2. Allow the ice machine to run a normal freeze cycle
(do not initiate an early harvest cycle).
3. At the start of the harvest cycle feel the compressor
discharge line and the liquid line to the ice machine
receiver at the head pressure control valve. The
temperature of both lines will be highest at the
beginning of the harvest cycle and then decrease.
Compare the lines 30 seconds into the harvest cycle.
Part Number: 000015431 Rev01 5/19 163