Service manual

39
Installation and Service Manual
COMPONENT DIAGNOSTICS
4 RELAY CIRCUIT BOARD SEQUENCE OF OPERATION
4 Relay Circuit Board Sequence of Operation
Place the toggle switch to the ice making mode. This en-
ergizes 3 of the 4 control board relays to activate the dump
solenoid, compressor contactor (a pump down solenoid on a
remote system), fan motor and the water pump. See note "A"
for dump switch setting. The dump solenoid relay will de-ener-
gize 6 to 9 seconds into the freeze cycle, terminating the dump
cycle.
Relay operation and special and special amber signal func-
tions on the control board are indicated by the 7 LEDs (3 Green,
3 Amber and 1 Red):
Green LED: Water pump, fan motor, dump solenoid,
compressor contactor and pump down
solenoid on remote systems.
Amber LED: Water curtain 1 and/or 2 and power ON
signal
Red LED: Hot gas solenoid
The ice forms to its predetermined thickness and rolls
over the evaporator bottom extrusion and covers the ther-
mistor tip. The ice increases the thermistors' resistance
- this signals the termination of the freeze cycle and the
de-energizing of the water pump and fan relay (Green
LED). The hot gas solenoid realy (Red LED) is ener-
gized. This is accomplished at about 26
o
F (-3.3
o
C).
NOTE: The condenser fan on remote models is
wired direct to the power line and may op-
erate throughout the harvest cycle. (See
wiring diagrams)
As the hot gas warms the evaporator(s), the ice is
released. When the ice is released from the evaporator(s)
it momentarily moves the water curtain(s) open. This
movement removes and returns the magnet to the Hall
switch(es), resetting the control board circuit to the next
ice making mode. The dump solenoid may be energized
at this time if the required number of harvest cycles have
occurred. This ice making cycle will repeat until the stor-
age bin is full.
* When the ice fills the bin it will hold the water
curtain(s) in the open position. With an open water
curtain(s), the Hall switch(es) will signal the control board
holding circuit for the de-energizing of the compressor
relay (Green LED) shutting down the ice machine after
30 seconds. The power on (Amber LED) is the only LED
operational in a "full bin" mode, except on C-12 - one
curtain may indicate bin full, 2nd may close, lighting LED.
Removal of ice from the bin will allow the water curtain(s)
to close completing the Hall switch circuit(s) reactivating
the ice making cycle.
NOTE: The cuber can be placed in the harvest mode
(hot gas defrost) at any time during the freeze
cycle by depressing the manual harvest
switch. To terminate the harvest cycle, mo-
mentarily open the water curtain(s).
The cuber will not initiate a freeze or harvest
cycle with the water curtain(s) open or re-
moved. Once the freeze cycle has been initi-
ated, the water curtain(s) can be open or re-
moved at any time.
* On remote system, the shut-down of the com-
pressor will be through the pump down control.
The compressor will continue to operate until the
system low side pressure is reduced to 13 PSI
(.90 Bars). On start-up the pump down solenoid
opens allowing the low side pressure to reach
45 PSI (3.10 Bars) closing the control contacts
allowing the compressor to start.
Effective with ice machines shipped from Servend
on September 1, 1994 the following changes were in-
corporated into the 4 relay circuit boards.
1. There is a delay programed on the board to dis-
regard the thermistor at the start of the ice mak-
ing cycle. This delay of eight minutes is to prevent
the thermistor from going into the harvest cycle
prematurely. Premature harvest may occur be-
cause of slushing conditions, water conditions,
remote pull down, etc. This delay can be bypassed
if you press the manual harvest switch on Solitech
circuit boards for the next cycle.
2. There is a maximum harvest time of nine min-
utes placed in the circuit. This will prevent the
machine from staying in harvest too long. The
unit will automatically reset itself if it is in a long
harvest. A situation like this can occur if the ice
bridge is set too thin, the evaporator is dirty or
the unit is in premature harvest.
3. A change was made to keep the hot gas sole-
noid valve open until the water curtain closes or
15 seconds elapses with the curtain open if the
unit is in a bin full mode. In the past, the hot gas
solednoid valve was de-energized when the cur-
tain began to open. In the event the machine