Form O-Y P/N 273647R5, Page 15
FIGURE 16 - Cooling Circuit B with Optional Bypass Valve (Option AUC8)
Model JDHA 120 and 150 (Cabinet 1) with Option AUC8
Model JDHA 180, 210, and 240 (Cabinet 2) with Option AUC8
Model JDHA 300 and 360 (Cabinet 3) with Option AUC8
Circuit B with Optional Hot Gas Bypass
Hot Gas Bypass Check Valve at the Evaporator Coil
Condenser Coil
Circuit B
Condenser Coil
Circuit A
View from Compressor and
Condenser Section
Hot Gas
Bypass Valve
Modulating
Compressor
(Circuit A)
Compressor
(Circuit B)
Compressor
(Optional Circuit DH)
Shutoff
Valve
Condenser
Coil - Circuit B
Hot Gas
Bypass Valve
Shutoff
Valve
Equalizer
Tube
Low Ambient Control,
Option BE8
If equipped with low ambient control, cooling is allowed to operate with an outside air tempera-
ture as low as 35°F (1.7°C).
Low Ambient Control for standard condenser fans (Option BE8
with Fan Option CUF3)
The electronic head pressure control modulates condenser fan motor speed in
low temperatures, varying the air volume through the condenser to regulate head
pressure. This model’s dual sensor input allows for the control of one or two
independent refrigerant circuits sharing the same fan motor(s). Only open, drip
proof, PSC or Shaded Pole motors are applicable for motor speed regulation. The
Controller monitors the liquid line temperature(degrees of excessive sub-cooling)
which is directly proportional to the head pressure. Speed modulation begins at 80°F
liquid line and proportionally reduces the fan to minimum speed once the liquid line
temperature reaches 50°F. Motor is turned off at liquid temperatures below or equal to
50°F. At 53°F the fan restarts at full speed; then modulates to minimum speed. When
the liquid temperature is 50°F and below the condenser fan motor will cycle between
minimum RPM and off to maintain proper condenser temperature (head pressure).
The above describes a 30ºF span (80ºF to 50ºF) function; a 25ºF span is also
available. The 25ºF span is recommended for High Efficiency systems; 30ºF span for
typical systems. Variable condenser airflow is modulated from full to minimum speed
over the selected span.
Option BE Pressure
Controller with Fan
Option CUF3,
P/N 261041
Use Temperature
to Resistance table
shown on right to
verify proper sensor
operation.
Temperature to
Resistance Table
