Refrigeration System - Follett Horizon Elite HC-1810R/N Operation And Service Manual

Refrigeration system

Condenser unit operation
The condensing unit is weatherproof and equipped to operate in ambient temperatures from –20 F to 120 F
(–29 C to 48.9 C). The condensing unit is controlled by a low and high pressure switches, which works in concert
with a refrigerant solenoid valve on the evaporator module. On start-up, the refrigerant solenoid valve opens
and suction pressure rises above the "on" set point of the high pressure switch. The compressor and fan turn
on and the refrigeration system operates. Upon shut down, the refrigerant solenoid closes. The compressor will
pump down the ice machine evaporator and suction line until the low "off" set point of the low pressure switch
is reached, at which point the compressor and fan will turn off.
Low ambient operation: Reliable operation at low outdoor ambient temperature is achieved with a pumpdown
cycle, a crankcase heater and a head pressure control valve. When the outdoor ambient falls, the condensing
pressure falls. This causes the discharge pressure to fall as well. When the discharge pressure falls below the
dome pressure, the valve modulates open to the discharge port which allows discharge gas to bypass the
condenser. Mixing the discharge gas with the liquid creates a high pressure at the condenser outlet, reducing
the flow and causing liquid to back up in the condenser. Flooding the condenser reduces the area available for
condensing. This reduction in effective condenser surface area results in a rise in condensing pressure. During
summer conditions, the discharge pressure is high, thus closing the discharge port of the valve. Hence, there is
full liquid flow from the condenser to the receiver.
A check valve is installed in the liquid line between the liquid receiver and the condenser to prevent liquid
migration from the receiver to the condenser during the off cycle. A second check valve is installed in the
discharge outlet of the motor compressor to prevent any oil from migrating onto the compressor head during
an off cycle. A low pressure control will start the condensing unit anytime the low side pressure rises above the
C/I setting of the control. The system contains a crankcase heater which is energized via the auxilliary contactor
of the compressor during any off cycle. It is de-energized whenever the compressor is energized. This keeps
the oil temperature in the compressor sump warmer than any other wetted surface to prevent liquid migration
from settling into the compressor sump to prevent flooded compressor starts in extreme outdoor temperatures.
The liquid receiver also contains a heater which is controlled by a thermostat and is de-energized above 80°F.
This is to maintain sufficient refrigerant pressure at extreme outdoor temperatures to activate the pressure
switch.
1810 -
Operating Pressure (Discharge PSIG/Suction PSIG)
Water Temperature F/C
F 50 60
C 10 16
60
182/27 182/27
16
70
188/28 188/28
21
80
218/30 218/30
27
90
249/32 249/32
32
100
282/34 282/34
38
HC_1810R/N, HC_2110R/N, HM_1810R/N, HM_2110R/N
70 80 90
21 27 32
182/27 182/27 183/27
188/28 188/27 188/27
218/30 218/30 219/30
249/32 249/32 249/32
282/34 282/34 282/34
2110 -
Operating Pressure (Discharge PSIG/Suction PSIG)
Water Temperature F/C
F 50 60
C 10 16
60
189/28 188/28 189/28 188/27
16
70
192/28 191/28 192/28 192/28
21
80
220/29 219/30 219/30 219/31
27
90
252/33 252/33 252/33 252/33
32
100
285/35 285/35 284/35 284/35
38
70 80 90
21 27 32
186/27
191/28
220/31
252/33
285/34
29