HA4AM ELECTRIC MOTOR
COMPENSATED REGULATOR
OPERATION
The regulator pressure setting is altered as the motor
receives a signal from a suitable temperature
controller. The motor responds to maintain the balance
in the electrical circuit. The rotation of the motor is
transmitted through a cam, valve stem, and range
spring to the top of the control module diaphragm. An
increase in temperature decreases the range spring
force on top of the control module diaphragm. This
decrease in force on the diaphragm allows inlet
pressure to pass through the control module to enter
the space on top of the piston which forces the main
valve seat open to reduce the evaporator pressure. A
decrease in temperature causes an increase in the
range spring force. This restricts the flow of inlet
pressure to the piston causing a reduction in the
opening of the main valve seat, reducing regulator flow
by raising the pressure setting.
APPLICATIONS
This motor compensated regulator is popular for fruit
storage, precision air temperature control, and liquid
chiller control.
ADJUSTMENT
Adjust the temperature controller as specified by the
manufacturer. Fully open the regulator manually by
turning in (clockwise) the manual-opening stem to cool
the product or room. Once the temperature at the
sensing device is approximately as desired, adjust the
controller output so that the cam is rotated to the
center position. Put regulator back in automatic
operation by turning the manual-opening stem out
(counterclockwise). Loosen the adjustment locking nut.
See the diagram to the right. Turn the adjustment stem
clockwise to raise the inlet pressure setting or
counterclockwise to lower the inlet pressure setting.
When the desired refrigerant pressure setting is
achieved, tighten the adjustment locking nut. A final
adjustment should be made after the system has
operated for a period of time.
Using a potentiometer slide wire type of controller
(typically 135 ohm), depending on product heat load, a
deviation from desired temperature of about +2F to +5F
(+1.1°C to +2.8°C) is normal to rotate the regulator cam
for maximum load satisfaction. As the load is reduced
or as the temperature becomes lower, the cam rotates
to create a higher evaporator pressure just adequate to
balance the load and maintain the desired temperature,
usually with ±1°F (0.5°C). Other controllers are available
to operate the motor/cam rotation.
The basic Electric Motor Compensated Regulator
consists of a nonremovable control module with a
motor bracket and cam. The control module is available
in either Range A, 0 to 150 psig (0 to +10 bar); or Range
V, 20" to 130 psig (–0.67 to +9 bar). The motor bracket
comes mounted on the control module and is suitable
for use with either PENN (standard) or HONEYWELL
motors. Two cams are available: Low Rise (standard)
and High Rise. The table below indicates the pressure
change possible for each cam and motor combination.
The PENN motor (standard) has 270° of rotation travel
and the HONEYWELL motor has 160° of rotation travel.
Motors are available for either 135 ohm or 4–20 mA
control signal input and require 24 VAC power input.
Electric proportional thermostat controllers (135 ohm
output), electronic PID controllers (4–20 mA output)
with sensor, and 24V transformers are available
accessories.
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