Control Sequence - Scotsman MCS 46 A Service Manual

Page 18
Meanwhile, the refrigerant as hot gas, discharged
from the compressor, flows through the hot gas
valve directly into the evaporator serpentine by-
passing the condenser.
The hot gas circulating into the serpentine of the
evaporator warms up the copper molds causing
the defrost of the ice cubes. The ice cubes,
released from the cups, drop by gravity onto a
slanted cube chute, then through a curtained
opening they fall into the storage bin.
At the end of the defrost cycle, both the hot gas
and the water inlet valves close and the machine
starts again a new freezing cycle.
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.
Once completed the freezing cycle 2nd phase
the system goes automatically into the defrost
cycle which also has a pre-fixed length. At
completion of the defrost cycle the P.C. BOARD
commands 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
partÌcular phase of the icemaking cycle.
BEGINNIING FREEZE
Electrical components (Loads) .
Compressor ..................................
Fan Motor (Air cooled only) and TRIAC
Hot Gas Valve ..............................
Inlet Water Valve ..........................
P.C. Board Relay 1 Coil ...............
P.C. Board Relay 2 & 3 Coil .........
Water Pump .................................
Contactor Coil ..............................
Electronic Timer ...........................
Electronic Controls & Sensors .. ON OFF
Evaporator Sensor .......................
Condenser Sensor .......................
Ice Level Control ..........................
TIMED FREEZE
Electrical components (Loads) .
Compressor ..................................
Fan Motor (Air cooled only) and TRIAC
Hot Gas Valve ..............................
Inlet Water Valve ..........................
P.C. Board Relay 1 Coil ...............
P.C. Board Relay 2 & 3 Coil .........
Water Pump .................................
Contactor Coil ..............................
Electronic Timer ...........................
Electronic Controls & Sensors .
Evaporator Sensor .......................
Condenser Sensor .......................
Ice Level Control ..........................
HARVEST (Drain portion - first 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 .................................
HARVEST (Water filling portion)
Electrical components (Loads) .
Compressor ..................................
ON OFF
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 .........................
Electronic Controls & Sensors .
•
Evaporator Sensor .......................
•
Condenser Sensor .......................
•
Ice Level Control ..........................
Page 18
ON OFF
•
• •
•
•
•
•
•
•
•
ON OFF
•
• •
•
ON OFF
•
•
•
•
•
•
•
•
•
•
ON OFF
•
•
•
•
•
•
•
•
•
•
ON OFF
•
•
•