Scotsman MC 45 Manual de servicio descargar pdf (Pagina 20)

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The electrical components in operation during

the freezing cycle are:

COMPRESSOR

FAN MOTOR (in air cooled version)

WATER PUMP

CONTACTOR COIL

and during the second phase of freezing cycle

(Time mode) they are joined by the

ELECTRONIC TIMER

The refrigerant head pressure, in the course of

the freezing cycle, ranges between 18 and 16

bars (250-225 psig) being controlled by the tem-

perature sensor probe located within the

condenser fins (air cooled version) or, on the

condenser tube coil (water cooled version).

On the air cooled version, the condenser tempe-

rature sensor, when senses a rising of the

condenser temperature beyond the pre-fixed

limit, changes its electrical resistance and send a

low voltage power flow to the Micro Processor of

P.C. BOARD which in turn energizes, through a

TRIAC, the FAN MOTOR.

When the opposite situation occures, i.e. the

condenser temperature gets below the pre-fixed

limit, the temperature sensor changes again its

electrical resistance reducing therefore the current

flow to the P.C. BOARD to cause the fan motor

temporary cut-off.

NOTE. On this model the condenser sensors

are used just to switch off the unit in case the

condensing temperature rise up to more then

C (for air cooled version) or more then

C (for water cooled version) for one of the

following abnormal reasons:

CLOGGED CONDENSER (Air cooled

version)

FAN MOTOR OUT OF OPERATION (Air

cooled version)

INSUFFICIENT FLOW OF COOLING

WATER (Water cooled version)

AMBIENT TEMPERATURE HIGHER THEN

C (100

it causes the total and immediate SHUT-OFF

of the machine in order to prevent the unit

from operating in abnormal and dangerous

conditions.

When the ice maker stops on account of this

protective device, there is a simultaneous

glowing of the RED LED, warning the user of

the Hi Temperature situation.

After having efiminated the source of the

condenser hi-temperature, to restart the

machine it is necessary first, to rotate for a

while the program selector on RE-SET

position then, to rotate it again on

OPERATION position.

The same can be done by just switching OFF

and ON the unit at main line switch.

The ice machine resumes its normal operation

by going through the 5 minutes water filling

phase.

At the start of the freezing cycle the refrigerant

suction or lo-pressure lowers rapidly to 2.5 bars-

35 psig then it declines gradually - in relation with

the growing of the ice thickness - to reach, at the

end of the cycle, approx. 1.6 ÷ 1.7 bar - 22 ÷ 24

psig with the cubes fully formed in the cup molds.

The total length of the freezing cycle ranges f rom

20 to 25 minutes.

DEFROST OR HARVEST CYCLE (Fig. C)

As the electronic timer has carried the system

throughout the second phase of freezing cycle,

the defrost cycle starts.

ATTENTION. In case the unit be able to

reach 0°C (32°F) evaporating temperatu-

re within 15 minutes, but after 45 minutes

from the beginning of the freezing cycle it

has not yet reached the evaporator tem-

perature of -15°C (5°F) the machine goes

straight into the defrost cycle omitting

the timed portion of the freezing cycle

relied to the setting of the first four DIP

SWITCHES.

NOTE. The length of the defrost cycle is pre-

determined by the setting of the DIP SWITCH

KEYS NO. 5, 6 and 7 and it is relied as well

to the ambient temperature as detailed in

Table C.

The electrical components in operation during

this phase are:

COMPRESSOR

WATER PUMP

WATER INLET SOLENOID VALVE

HOT GAS SOLENOID VALVE

WATER DRAIN SOLENOID VALVE/S

for the first 15 ÷ 20 seconds.

The incoming water, passing through the water

inlet valve and the flow control, runs over the

evaporator platen and then flows by gravity

through the dribbler holes down into the sump/

reservoir (Fig. D).

The water filling the sump/reservoir forces part of

the surplus water from the previous freezing

cycle to go out to the waste through the overflow

pipe. This overflow limits the level of the sump

water which will be used to produce the next

batch of ice cubes.

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.

NOTE. The length of the defrost cycle, factory

set, can change according to the ambient

temperature (as shown on Table C) in order

to reduce it with high ambient temperature

and recover some of the time spent for the

longer freezing cycle.

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 36 37

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