JDF Silver Series Training Manual
16
Refrigeration System
The components that make up the refrigeration system to create an ice
bank are compressor (1), filter dryer with capillary tube (2), condenser
(3), condenser fan (4), evaporator (5) and accumulator (6). The other
components that are responsible for monitoring the ice bank and turn-
ing on/off of the compressor are as follows; thermistor (7), start relay (8),
run relay, transformer and main control board.
Upon initial plug-in or power up, the main control board will monitor the
bath thermistor and go through a six minute delay sequence before sup-
plying 120VAC to the compressor
relay coil. After the six minute de-
lay, the run relay coil will energize,
power cannot pass through the
relay contacts until the refrigeration
switch is turned to supply power to
the compressor.
Power passes through the limit thermostat and powers the start relay mounted on the compressor. The unit will take
several hours to create the ice bank required for full dispenser performance. During this time, some further trickling
from the water bath is expected due to expansion caused by the ice bank formation. When the temperature reaches
27º F, this will shut off the 120VAC to the compressor run relay coil. As the ice block thaws, temperature rises to 32º
F, the CBA will again supply 120VAC to the compressor run relay coil to start the compressor. Anytime the machine is
powered down electrically, the refrigeration system will have a six minute delay starting the compressor.
The delay ensures enough allowable time for the start relay (PTC) resistance to decrease to complete the start wind-
ing path for initial start up and refrigerant high and low pressure to stabilize.
Cabinet Cooling
First, the refrigeration system creates an ice block around the evaporator coil in the bath tank. The top load recircu-
lating pump is mounted semi-centered in the bath tank and is activated by the refrigeration switch. Water is drawn
from the bath tank up to the top connection of the cabinet cooling coil and at the same time water is being bypassed
going directly back into the bath tank for increased agitation. The chilled water passes through the cabinet water coil
picking up heat before returning back to the bath tank along side of the recirculating pump. Water is being bypassed
at all times during this 24/7 recirculation process.
Meanwhile, a 24VDC cabinet fan operates
24/7 pulling and recirculating the cabinet
air across the cabinet water coil. This
speeds up the process of removing heat
from the cabinet air or decrease the cabinet
temperature. A thermistor located inside
the cabinet behind the fan panel monitors
the temperature. The CBA will receive the
low input voltage signal and will turn on the
corresponding temperature LED’s located
at the bottom of the CBA. The #5 green
LED indicates cabinet temperature is below
50º F and #4 red LED indicates cabinet
temperature is above 50º F. A thermistor
can also be used to detect rise in
temperature for a period of time and signal
a fault status. The nominal cabinet holding
temperature is expected to be at or below 41º F.
Summary of Contents for JDF Silver Series
Page 1: ...BUNN TECHNICAL TRAINING JDF Silver Series ...
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