Control Sequence - Scotsman ACM 85 Service Manual

Page 22
OPERATION - CONTROL SEQUENCE
At the start of freezing cycle the evaporator
temperature sensor controls the length of the first
part of the freezing cycle. As it reaches a
predetermined temperature it supplies a low
voltage current to the P.C. BOARD in order to
activate the electronic timer which takes over the
control of the freezing cycle for a pre-fixed time
according to the DIP SWITCH keys setting
(see Tab. B).
NOTE. The evaporator temperature sensor,
factory pre-set, is the same for all the models
and is not adjustable in the field.
Once completed the freezing cycle 2nd phase
the system goes automatically into the defrost
cycle which has also a pre-fixed length that can
slightly change in relation to the ambient tempe-
rature as shown in Table C. At completion of the
defrost cycle the P.C. BOARD command the unit
to start again a new freezing cycle.
OPERATION - ELECTRICAL SEQUENCE
The following charts illustrate which switches
and which components are ON or OFF during a
particular phase of the icemaking cycle.
Refer to the wiring diagram for a reference.
BEGINNING FREEZE
Electrical components (Loads)
Compressor ...........................................
Fan Motor (Air cooled only) and TRIAC ........
Hot Gas Valve ........................................
Water Inlet Valve ....................................
Water Drain Valve ..................................
P.C.Board Relay 1 Coil ..........................
P.C.Board Relay 2 & 3 Coil ....................
Water Pump ...........................................
Contactor Coil ........................................
P.C.B. Timer ...........................................
Elctronic Controls & Sensors
Evaporator Sensor .................................
Condenser Sensor .................................
Ambient Sensor ......................................
Ice Level Control ....................................
TIMED FREEZE
Electrical components (Loads)
Compressor ............................................
Fan Motor (Air cooled only) and TRIAC ........
Hot Gas Valve ........................................
Water Inlet Valve ....................................
Water Drain Valve ..................................
P.C.Board Relay 1 Coil ..........................
P.C.Board Relay 2 & 3 Coil ....................
Water Pump ...........................................
Contactor Coil ........................................
P.C.B. Timer ...........................................
Electronic Controls & Sensors
Evaporator Sensor .................................
Condenser Sensor .................................
Ambient Sensor ......................................
Ice Level Control ....................................
HARVEST (Drain portion - first 15 or 30 sec.)
Electrical components (Loads)
Compressor ............................................
Fan Motor (Air cooled only)and TRIAC .........
Hot Gas Valve ........................................
Water Inlet Valve ....................................
Water Drain valve ...................................
P.C.Board Relay 1 & 2 Coil ....................
P.C.Board Relay 3 Coil ...............................
Water Pump ...........................................
Contactor Coil ........................................
P.C.B. Timer ...........................................
Electronic Controls & Sensors
Evaporator Sensor .................................
Condenser Sensor .................................
ON OFF
Ambient Sensor ......................................
•
Ice Level Control ....................................
•
•
HARVEST (Water filling portion)
•
Electrical components (Loads)
•
Compressor ............................................
•
Fan Motor (Air cooled only)and TRIAC .........
•
Hot Gas Valve ........................................
Water Inlet Valve ....................................
•
Water Drain valve ...................................
•
P.C.Board Relay 1 & 2 Coil ....................
•
P.C.Board Relay 3 Coil ...............................
Water Pump ...........................................
Contactor Coil ........................................
P.C. Board Timer ...................................
ON OFF
•
Electronic Controls & Sensors
Evaporator Sensor .................................
•
Condenser Sensor .................................
•
Ambient Sensor ......................................
•
Ice Level Control ....................................
ON OFF
•
• •
•
•
•
•
•
•
•
•
ON OFF
•
• •
•
•
ON OFF
•
•
•
•
•
•
•
•
•
•
ON OFF
•
•
•
•
ON OFF
•
•
•
•
•
•
•
•
•
•
ON OFF
•
•
•
•