23
IV. Service Diagnosis
A. 10-Minute KM Diagnostic Procedure
The 10 minute check out procedure is basically a sequence check which can be used
at unit start-up or for system diagnosis. Using this check out procedure will allow you
to diagnose electrical system and component failures in approximately 10 minutes
under normal operating conditions of 70°F (21°C) or warmer air and 50°F (10°C) or
warmer water temperatures. Before conducting a 10 minute checkout, check for correct
installation, proper voltage per unit nameplate, and adequate water supply. Check
the S4 dip switch settings to assure that #3, 4, 7, 8, 9, & 10 are in the factory default
position. Switches 1, 2, 5, & 6 are cleaning adjustments and the settings are flexible. For
factory default settings, see "II.C.3.a) Default Dip Switch Settings." As you go through
the procedure, check to assure the components energize and de-energize correctly.
If not, those components and controls are suspect. Check for voltage at the 10-pin
connector.
1) Turn power off and access the control box.
2) Turn power on and place the control switch in the "ICE" position. A 5 second delay
occurs. The red "POWER OK" LED on the control board comes on.
3)
One Minute Fill Cycle
– LED 4 is on.
The inlet water valve is energized. After
1 minute, the control board checks the float switch. If the float switch is closed, the
unit cycles to harvest. If closed, continue to step 4. If the float switch is open, the unit
repeats the 1 minute fill cycle until water enters and the float switch closes (low water
safety protection during initial start up and at the end of each harvest).
Diagnosis:
If
the inlet water valve does not open, check for no supply voltage at inlet water valve
terminals, bad coil, or plugged screen or external filter (no water flow). If unit fails to
start harvest, check for open float switch or bad 1 minute timer in control board.
4)
Initial Harvest Cycle
–
LEDs 1, 4, and 2 are on.
The inlet water valve remains
energized, the contactor coil energizes to start the compressor, and the hot gas valve
energizes. The inlet water valve is open during harvest for a maximum of 6 minutes or
the length of harvest which ever is shorter. The evaporator warms and the thermistor
senses 48°F (9°C). The control board then receives the thermistor's 3.9 k
Ω
signal and
turns operation of harvest over to the harvest timer. The harvest timer has settings of
60, 90, 120, and 180 seconds (S4 dip switch 1 & 2). When the harvest timer countdown
is complete, the freeze cycle starts.
Diagnosis:
Check if compressor is running,
hot gas valve is open, inlet water valve still open. Average harvest cycle at factory
setting is 2 to 3 minutes. How long does initial harvest last? 1.5 minutes after initial
harvest begins, touch the compressor discharge line. Is it hot? If not, check refrigerant
pressures and compressor operation. If it is hot, touch the inlet line to the evaporator.
Is it hot? If it is hot and the freeze cycle is not starting, check the harvest timer
adjustment, the thermistor for open circuit, the discharge line temperature, compressor
efficiency, and if the hot gas valve is fully open.
