Electrically Compensated
Pressure Regulators
Type A4AM-DN, A4AOM-DN, & A2BM-DN
PORT SIZE 3/8”-4” (20-100MM)
FOR AMMONIA, R22, R134A, R502
OTHER COMMON REFRIGERANTS
FEATURES
• Unique modular construction
• Suitable for all common refrigerants and oils
• Easy to service
• Interchangeable parts
• 362 psig (25 bar) design pressure (PS)
• Pilot operated characterized Modulating Plug for precise
control
• Manual opening stem
• Close coupled strainers, optional
• Stainless steel diaphragm
• Flanges for threaded or welded steel pipe and copper tube
(copper not for ammonia)
• Available in most standard R/S regulator variations
(A4AMS, A4ADM, etc...)
• Complies with Pressure Equipment Directive 97/23/EC
BULLETIN DN23-11
Type A4AM-DN
Februay 2002
Installation and Service Information
Description:
These heavy duty, pilot operated pressure regulators are
suitable for R-717, R-22, R-502 and other common refrigerants and fluids approved for use in refrigeration systems. All A4
Regulators are pilot operated using upstream pressure for the
opening force and require a minimum 2 psi (0.14 bar) pressure
drop to fully open. These valves are generally ordered with a
close coupled upstream strainer to prevent the entrance of
foreign material into the valve and the rest of the system. The
fluid temperature range for the A4 Series of Regulators is -50F
to 220F (-45C to 105C).
Fig. 1 A4AM
Refrigerating Specialties Division
310219
PURPOSE:
These electrically compensated A4AM inlet pressure regulators modulate the flow of refrigerant gas or liquid to maintain a
varying upstream (or inlet) pressure in response to an electrical
signal applied to a low voltage motor mounted on a regulator
pilot. When supplied with Range D, they also can be used to
control condensing pressures; for example, as part of a heat
reclaim system.
These regulators are excellent in controlling evaporator pressure/temperature where load fluctuations are great, such as
hot carcass chilling, warm fruit and wine chilling and cooling
tunnels. They are also useful where product load is fairly
constant but very close temperature or humidity control is
desired.
When the regulator is used in a location where excessive
moisture, corrosion or explosive atmosphere exists, or in low
temperature applications where ice could accumulate on the
pilot valve stem, the A4AR with A2BM remote pilot can be used.
(See Fig. 7)
1
ISO 9001 CERTIFIED
Important Note:
The motor cover should be kept on the motor at all times to
protect it from dust and mechanical damage. No lubrication of
the motor is required.
PRINCIPLES OF OPERATION, A4AM (SEE FIG. 1)
The motor will respond to a signal from a suitable controller, for
example, a thermostat. When the temperature at the sensing
element changes the thermostat, the motor responds immediately to the signal by rotating the motor shaft. This rotation is
transmitted through the cam to the valve stem and range spring
to change the set-point by changing the spring pressure acting
on top of the diaphragm. Whether used as part of a cooling
system to control evaporator pressure, or as part of a heat
reclaim system to control condensing pressure, an increase in
temperature at the thermostat will decrease the spring pressure and lower the inlet pressure thus lowering the evaporator
or condenser temperature. Normally cam rotation is 160 degrees and one minute of time is required for the full cam
rotation. A motor with 240 degrees and 1.5 minute rotation time
is available and must be so ordered.
The principles of operation of the A4AM Series are the same as
for the basic A4 regulator except for the varying set-point of the
motorized pressure pilot. The inlet refrigerant pressure enters
the space under the diaphragm through passage N. When the
force created by the inlet pressure exceeds the varying spring
force, the diaphragm is lifted off of the pilot seat allowing
pressure to enter the top of the power piston. This causes the
power piston to move downward forcing the modulating plug to
open and modulate to maintain the varying set-point pressure
as dictated by the temperature controller signal to the motor.
An increase in refrigerant inlet pressure, above the set-point
pressure setting, lifts the diaphragm further to allow more
pressure on top of the power piston and opens the valve wider.
A decrease in inlet pressure, below the varying set-point
pressure setting, causes the diaphragm to move closer to the
pilot seat reducing the pressure to the top of the piston and
causing the closing spring to reduce the valve opening. The
pressure on top of the piston is controlled by the flow through
the bleed hole in the power piston and through the clearances
between the piston and main valve cylinder. A minimum of 2
psi (0.14 bar) pressure drop across the valve is required in
order for it to open fully.
ADJUSTMENT A4AM
Adjust the controller sensitivity to the desired point according
to the manufacturer’s directions. Open the regulator manually
(manual opening stem backed out) and run the system until the
temperature at the sensing element reaches the desired level.
Adjust the controller (thermostat) setting to a reading that will
cause the cam of the motor to rotate and stop in center cam
position. Put the regulator back into automatic operation by
turning the manual opening stem in until just the flats on the
stem are visible. Loosen the pressure adjusting screw lock nut
and turn the adjusting screw until the desired inlet pressure for
this temperature and load condition is reached. Turning the
adjusting screw in will lower the pressure; turning it out will raise
the pressure. If after several hours of operation the temperature is not as desired, readjust the pressure adjusting screw
slightly. Once the desired setting is reached, make sure the
lock nut is tightened. The valve will now modulate in response
to load variation to maintain constant temperature.
PRINCIPLES OF OPERATION, A4AOM (SEE FIG. 2)
This pressure regulator modulates the outlet pressure in accordance to load requirements as sensed by an electric thermostat or humidistat that varies an electric signal applied to a
motor mounted on the regulator pilot. The motor operation is
described above for A4AM, except the A4AOM operates as an
outlet pressure regulator. Available in standard Range V or
Range D.
The outlet pressure is sensed under the diaphragm through the
sensing tube, which is part of the Flange Ring-tube assembly.
When the force created by the outlet pressure acting under the
diaphragm is less than the force of the range spring, the pilot
plug is open, allowing pressure to enter on top of the piston.
This causes the power piston to force the throttling plug to open
to maintain constant outlet pressure. Decrease in the outlet
pressure allows the range spring to open the pilot plug further,
allowing more pressure on top of the piston and opening the
throttling plug further. An increase in the outlet pressure will lift
the diaphragm against the force of the range spring, allowing
the pilot plug to start closing. The pressure on top of the power
piston is decreased and the closing spring acts to reduce the
opening of the throttling plug and the flow of fluid through the
regulator. The pressure on top of the power piston is controlled
by the flow through the pilot seat and the bleed through a bleed
hole in the power piston and through the clearance between
the piston and the cylinder. A minimum of 2 psi (0.14 bar)
pressure drop across the regulator is required to open it fully.
ADJUSTMENT A4AOM
Adjust the controller sensitivity to the desired point according
to the manufacturer’s directions. Open the regulator manually
(manual opening stem backed out) and run the system until the
temperature at the sensing element reaches the desired level.
Adjust the controller (thermostat) setting to a reading that will
cause the cam of the motor to rotate and stop in center cam
position. Put the regulator back into automatic operation by
turning the manual opening stem in. Loosen the pressure
adjusting screw lock nut and turn the adjusting screw until the
desired inlet pressure for this temperature and load condition
is reached. Turning the adjusting screw in will lower the
pressure; turning it out will raise the pressure. If after several
hours of operation the temperature is not as desired, re-adjust
the pressure adjusting screw slightly. Once the desired setting
is reached, make sure the lock nut is tightened. The valve will
now modulate in response to load variation to maintain constant temperature.
MANUAL OPENING STEM:
All Type A4 Regulators are provided with a manual opening
stem. To open the regulator manually, back the stem out (turn
counter-clockwise) until it stops. To put the regulator into
automatic operation, turn the stem in (clockwise) until only the
flats on the stem protrude from the packing nut.
Refrigerating Specialties Division
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Fig 2. A4AOM
OPTIONS
Ranges
Available in Ranges A, V and D. Honeywell motor has 160o cam
rotation which is equivalent to a change in set-point of 60 psi
(4.1 bar) for Ranges A or V, or 106 psi (7.3 bar) for Range D;
Penn motor has 240o cam rotation which changes set-point 90
psi (6.2 bar) for Ranges A or V, or 159 psi (10.9 bar) for Range
D.
Motors
Model: M9181A-1012 Honeywell Inc.
Features: Reversing, proportional motors used to operate
valves or dampers in electric modulating circuits. Oil immersed
motor and gear train for reliable performance and long life.
Wiring box provides NEMA 3 weather protection. Actuator
motor and circuitry operate from 24 volts AC. Fixed stroke,
o
.
160
No auxiliary switches. The controller type is a 135 ohm
Honeywell Series 90 proportional controller (See Fig. 10).
Model: M7284A-1020 Honeywell Inc.
Features: Electronic Modutrol motors used to control dampers
and valves. This motor accepts a current signal from an
electronic controller to position a damper of valve at any point
between open and closed. Oil immersed motor and gear train
for reliable performance and long life. Wiring box provides
NEMA 3 weather protection. Actuator motor and circuitry
operate from 24 volts AC. Fixed stroke, 160
o
. No auxiliary
switches. This motor is used with controllers that provide a
stable, noise-free proportional output of 4-20mA nominal,
25mA maximum (See Fig. 13).
Model: M6281A-1009 Honeywell Inc.
Features: Floating control motor with an internal electrically
isolated feedback potentiometer. This motor is used with
controllers that provide SPDT or floating output to operate
dampers or valves. The feedback potentiometer provides an
indication of the motors shaft position and can be used for
slaving Series 90 motors or rebalancing an external control
circuit. Wiring box provides NEMA 3 weather protection. Actuator motor and circuitry operate from 24 volts AC. Fixed stroke,
160o. No auxiliary switches (See Fig. 12).
Model: M6191B-1006 Honeywell Inc.
Features: Non-spring return, 3-wire floating control motor. This
motor is used with controllers that provide a switched or floating
SPDT output to operate dampers or valves. Actuator motor
and circuitry operate from 24 volts AC. Fixed stroke, 160o . One
(1), auxiliary switches (See Fig. 14).
Model: M150-JGA-1 Penn Johnson
Features: The M100J motor actuators are used to position
valves and dampers in heating ventilating, air conditioning,
refrigeration and industrial applications. The motor accepts a
Johnson Controls 0 to -2 VDC electronic controller input, or a
0 to +24 VDC input, or a 3-wire 135 to 1000 ohm potentiometer
input (See Fig. 11).
Refrigerating Specialties Division
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OTHER CONFIGURATIONS
A4AMS
Description
The Type A4AMS is an electrically compensated inlet pressure
regulator with a pilot electric shut-off. The integrally mounted
solenoid must be energized for the valve to function as a
regulator. When de-energized, the regulator is closed, regardless of inlet pressure.
Purpose
The Type A4AMS should be used whenever it is required to
stop all flow (in the normal fluid flow direction) through the
regulator. This could include use in defrost applications and as
part of a temperature control system.
The Type A4ADM is a Dual Inlet Pressure Regulator capable
of regulating at two (2) pressure levels, one a fixed set-point
and the other being the electrically compensated set-point.
When the integrally mounted S6A pilot solenoid valve is
energized, the regulator is controlling at the lower of two setpoints. This would be the electrically compensated low pressure pilot doing the controlling. When the pilot solenoid is deenergized the regulator is controlling at the higher set-point,
which must be adjusted on the bolt-on (outboard) pressure
pilot.
Note: The high pressure pilot must always be set higher than
what the electrically compensated pilot can reach in order to
prevent the high pressure pilot from controlling when not
required.
PRINCIPLES OF OPERATION, A4AMS
The operation of the A4AMS is the same as that described on
Page 2, except the inlet pressure from passage N must first
pass through the S6A pilot solenoid before it can reach the
diaphragm. Thus, the S6A pilot solenoid must be energized
before the A4AMS can begin to regulate, regardless of inlet
pressure (See also Bulletin D23-06).
Adjustment, A4AMS
With the solenoid pilot energized, proceed as described under
Adjustment A4AM.
A4ABM
Description
The Type A4ABM is an inlet pressure regulator with a pilot
electric wide opening feature. When the integrally mounted
solenoid is energized, the valve is wide open, thereby bypassing the regulator function; i.e., not regulating. However, in the
wide open mode the regulator will still require the 2 psi (0.14
bar) minimum pressure drop. When the solenoid is deenergized, the valve functions as an electrically compensated
inlet pressure regulator.
Purpose
The Type A4ABM frequently is used with the wide open
function, where maximum refrigeration capacity from the evaporator is required for some period of time. With the solenoid deenergized, the regulator is electrically compensated.
Principle of Operation A4ABM
The operation of the A4ABM is the same as that described on
Page 2 when operating as a regulator (pilot solenoid deenergized). When the solenoid is energized the upstream
pressure from passage N bypasses the underside of the
diaphragm and is fed directly to the top of the piston where,
provided a 2 psi (0.14 bar) pressure difference exists across
the main valve throttling plug will be held open (See also
Bulletin D23-06).
Adjustment, A4ABM
With the solenoid pilot electrically de-energized, proceed as
described under Adjustment A4AM.
A4ADM
Description
Purpose
The Type A4ADM uses are similar to those for the A4ABM
except, instead of operating in a wide open position when the
pilot solenoid is energized, the regulator is controlling the inlet
pressure through the motorized pressure pilot in response to
an electric signal from its controller.
Typical uses include capacity control of an evaporator at
different pressure levels to regulate temperature at varying
load conditions (Low pressure compensating pilot), and evaporator pressure control combined with defrost pressure relief
(high pressure pilot).
Principles of Operation, A4ADM
The operation of the A4ADM is similar to that described on
Page 2. When the Pilot Solenoid is energized, upstream
pressure from passage N is made available to both pressure
pilot diaphragms. Since the path of least resistance will be
through the pressure pilot with the lower set-point (lower range
spring force), that pilot will control.
When the pilot solenoid is de-energized, upstream pressure
from passage N can flow only to the higher pressure pilot,
which will then control the regulator (See also Bulletin D23-
06).
Adjustment A4ADM
Electrically de-energize the solenoid pilot and adjust the modular (bolt on) pressure pilot for the desired high pressure setting.
Remove the seal cap on top of the high pressure pilot (outboard
pilot) and turn the adjusting stem clockwise to increase setting
or counter clockwise to decrease setting. Final adjustment
should be made after the system has been operating for a
period of time. Electrically energize the pilot solenoid and
adjust the motorized pressure pilot (low pressure) as described
under Adjustment A4AM.
A2BM
Principles of Operation, A2BM (See Fig. 5)
The A2 type pressure regulators are compact, direct diaphragm operated, for use with refrigerant liquid or vapor. The
A2BM and A2AM are inlet pressure regulators that prevent inlet
(or upstream) pressure from falling below set-point. They will
tend to open on a rise in inlet pressure above set-point and will
be closed below set-point. The pressure regulator will have a
varying set point in accordance to load requirements as sensed
by an electric thermostat or humidistat that varies an electric
signal to a motor mounted on the regulator bonnet. The motor
operation is as described on Page 2 for A4AM.
Refrigerating Specialties Division
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