Scotsman AC 105 Service Manual page 11

Page 10
F. The ice making process takes place thereby,
with the water sprayed into the molds that gets
gradually refrigerated by the heat exchange with
the refrigerant flowing into the evaporator
serpentine. During the freezing process, when
the evaporator temperature falls below an
established value, the evaporator temperature
sensor supplies a low voltage power signal to the
electronic control device (P.C.BOARD) in order
to activate an electronic timer. This one takes
over the control of the freezing cycle up to the
complete formation of the ice cubes (Fig.4).
NOTE. The lenght of the entire freezing cycle
is governed by the evaporator temperature
sensor which has its probe placed in contact
with the evaporator serpentine (Non
adjustable) in combination with the electronic
timer (Adjustable) incorporated in the
P.C.BOARD. The timer adjustment is factory
set in consideration of the ice maker type,
cooling version and ice cube size (Small,
Medium, Large). It is possible, however, to
modify the timed lenght of the freezing cycle,
by changing the DIP SWITCH keys setting.
In Table B of PRINCIPLE OF OPERATION
are shown the various time extensions of the
freezing cycle second phase, in relation with
the different DIP SWITCH keys setting.
FIG. 5
- EVAPORATOR
- CONDENSER
- AMBIENT
Rx Tx
L
N
16
DIP
SWITCH
ELECTR.
15
TIMER
14
13
1
2 TRANSF.
G. After about 17÷20 minutes from the begin-
ning of the freezing cycle, in an hypothetic
ambient temperature of 21°C, the defrost cycle
takes place with the hot gas, the water inlet
and the water drain valves simoultaneously
activated (Fig. 5).
The electrical components in operation on models
are:
COMPRESSOR
WATER INLET VALVE
HOT GAS VALVE
WATER DRAIN VALVE
and the
WATER PUMP
on the first 15 seconds.
NOTE. The lenght of the defrost cycle (not
adjustable) is automatically determinated by
the micro-processor of the P.C. BOARD in
relation of the time necessary for the unit to
reduce the evaporator temperature from 0 ° C
(32 ° F) to -13 ° C (8.5 ° F) - TIME T2.
H. Check, during the defrost cycle, that the
incoming water flows correctly into the sump
reservoir in order to refill it and that the surplus
overflows through the overflow drain tube.
WATER DRAIN VALVE
7
8
9
10
RELAYS
3
4
5
TRIAC
6
RELAY
11
12
WATER IN VALVE
HOT GAS VALVE
CONTACTOR COIL
FAN MOTOR
WATER PUMP
ELECTRONIC CARD