Scotsman MAR1400 - Manual (Page 19)

Electrical Sequence:
After power has been connected, because the bin
thermostat bulb is warm, the water pump will start.
After water has been supplied to the machine, the
Time Delay Relay is energized and, after its preset
wait time has expired (about 8 - 10 minutes), it
connects power to the contactor coil and the liquid
line valve.
The gear motor begins to turn the drum.
When the bin thermostat opens the pump,
contactor coil, time delay relay coil, gear motor and
liquid line coil all open or stop.
The unit will not restart until the time set in the time
delay relay has expired.
* And all safety switches are closed.
PRINCIPLES OF OPERATION - HOW IT WORKS
1. ICE MAKER
The revolving drum is made of a cylinder shaped
skeleton covered by a stainless steel jacket.
Just under the stainless steel jacket is a channel,
about 15 m/m (9/16”) deep and 15 m/m wide. The
channel is in a spiral pattern that goes from one
end of the cylinder to the other.
Both ends of the channel are connected with a
bore made in the right cylinder journal. The
manifold on the right side is for both liquid
refrigerant inlet and vapor refrigerant outlet.
Since the cylinder’s stainless steel jacket is tightly
sealed onto the drum, the spiral pattern channel
made for the refrigerant flow becomes the
evaporator’s serpentine.
Metered refrigerant enters through the manifold
and enters the evaporator serpentine. There it
boils and evaporates as it comes into contact with
the drum’s metal jacket, reducing the temperature
of the drum. About one third of the cylinder drum is
constantly submerged in water. This allows the
cylinder metal jacket to draw a film of water that,
as soon as it comes out of the water, freezes
almost instantly due to the heat absorption created
by the boiling refrigerant circulating in the
serpentine.
On fresh water systems a water pump and water
distributor tube provide a constant flow of cold
water to the upper side of the evaporator drum.
The extra water increases the effective freezing
surface and results in a thicker ice layer.
The ice layer on the emerging cylinder then
quickly solidifies, dries and eventually subcools
before contacting the edge of the horizontal
scraping blade.
The heavy duty metal scraping blade causes the
ice sheet to peel off of the drum jacket by scraping
it as it advances on the revolving drum.
The ice sheet is so dry that, when it gets in contact
with the scraping blade, it cracks in a form of
irregular shaped chips.
The refrigerant leaves the evaporator serpentine
to return to the compressor via suction line
through the inner bore of the manifold.
The refrigerant is sealed in the inlet/outlet head
manifold by a specially designed sealing device.
The cylinder is driven by separate drive motor and
gear reducer located on the opposite side of the
refrigerant manifold.
The gear reducer, the driving belt with its pulley,
the revolving drum with the rotating part of the
sealing devices and the water pump on fresh water
installation are the mechanical parts in motion.
MAR1400 & MAR2000
December 2000
Page 19
Time Delay Relay, Set at Normal Delay Position
This light is
on when there
is power and
the bin
thermostat is
closed.*
This light is
on when the
other light is
on AND the
time delay
has expired.