Service manual
Section 7 Refrigeration System
Part No. 80-1206-3 7-25
Diagnosing Air Cooled Condensing Units
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 (completely bypass the
condenser) in the harvest cycle are:
• Freeze cycle suction and discharge pressure are
normal.
• The control board indicates safety limit #2. The
failure seems to be temperature related. Example:
The ice machine may function correctly at
temperatures above 32°F (0°C) but fails at
temperatures below 32°F (0°C).
• 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 headmaster 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 headmaster valve. The temperature
of both lines will be highest at the beginning of the
harvest cycle and then decrease. Compare the lines
for the first 30 seconds of the harvest cycle and then
refer to the chart below.
Harvest Cycle Headmaster Control Valve Failure List
CVD0675/CVD0875/CVD1075/CVD1285/CVD1475/
CVD1476/CVD1875/CVD2075
R
e
f
r
i
g
e
ra
n
t
Fl
o
w
No
F
low
Step 3 Details
Grasp Here with Hands to Compare Temperatures
LIQUID LINE TO
ICE MACHINE
RECEIVER
COMPRESSOR
DISCHARGE
LINE
LIQUID LINE
FROM
CONDENSER
SV3100
!
Warning
The compressor discharge line and the liquid line to
the receiver could be hot enough to burn your hand.
Touch them momentarily only.
Finding Comments
Temperature of the
compressor discharge line
and the liquid line to the ice
machine receiver feel the
same.
The headmaster is
functioning correctly.
The compressor discharge
line is noticeable warmer than
the liquid line to the ice
machine receiver.
Headmaster valve is not
bypassing 100%. Replace
headmaster valve.