Service manual

Refrigeration System Section 7
7-26
Part No. 80-1206-3
Diagnosing Water Cooled Condensing Unit
FREEZE CYCLE
The water regulating valve maintains the freeze cycle
discharge pressure. Refer to water regulating valve
diagnostics.
HARVEST CYCLE
The headmaster 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 headmaster valve
that will not seat 100% closed in the harvest cycle
(completely bypass the condenser) are:
• Freeze cycle suction and discharge pressure are
normal.
• The control board indicates safety limit 2.
• Harvest cycle suction pressure is low.
• Harvest cycle discharge pressure is normal or high
(water regulating valve attempts to maintain
240 psig)
Headmaster Control Valve Failure List
CVD1476
REFRIGERANT CHARGE VERIFICATION
QuietQube® remote ice machines require the correct
amount of refrigerant (name plate charge) to operate
correctly at all ambient conditions.
An ice machine with an over or under charge of
refrigerant may function properly at higher ambient
temperatures and fails at lower ambient temperatures.
Symptoms of incorrect refrigerant charge are:
• Works during the day and then malfunctions at night.
• Safety limit #2 in control board memory.
• Harvest cycle suction pressure is low.
When refrigerant charge is suspected, verify by
recovering the refrigerant, weighing and comparing to
the nameplate amount. Refer to “Refrigerant Recovery/
Evacuation” at the end of this section for recovery
procedures.
Problem Cause
Freeze Cycle
Valve not maintaining
discharge pressure.
The water regulating valve
maintains the freeze cycle
discharge pressure.
Discharge pressure
extremely high; Liquid line
entering receiver feels hot.
Verify water regulating valve
is set and/or operating
correctly. Headmaster valve
is stuck in bypass.
Discharge pressure low,
Liquid line entering receiver
feels warm to hot.
Ice machine low on charge.
Refer to “Low on Charge
Verification.”
Harvest Cycle
Discharge pressure normal or
high, Liquid line entering
receiver feels warm, suction
pressure is low.
Headmaster valve not
bypassing, Refer to “ Harvest
Cycle Headmaster Control
Valve Failure List” for
diagnostic procedure.
Problem Symptom
Undercharge Safety limit #2 in control board memory.
Harvest cycle suction pressure is low.
Harvest cycle discharge pressure is
low.
Liquid line entering receiver feels warm
to hot in the freeze cycle.
Depending on the amount of refrigerant
loss, the ice machine may harvest for
one or two cycles when restarted after
an “Automatic Shut-Off” (ice machine
pumped down and shut off on low
pressure control).
Overcharge Safety limit #2 in control board memory.
Harvest cycle suction pressure is low.
Harvest cycle discharge pressure is
normal.
Freeze cycle time, suction and
discharge pressure are normal and the
ice machine will not harvest. The sheet
of ice cubes show little or no sign of
melting when removed from the
evaporator after the harvest cycle has
been completed. (If the cubes are
melted you have a release problem,
clean the ice machine).