Refrigerating Specialties Division
2
Purpose
The purpose of the Type A4W Series of Pressure Regulators is to
modulate the fl ow of refrigerant gas and/or liquid so as to maintain
a constant set for pressure, regardless of load fl uctuations. The
regulators described in this bulletin control upstream (inlet)
pressure except for the Type A4WOE, which controls downstream
(outlet) pressure.
The fl uid temperature range for the A4W Family of Regulators is
-45° to 105°C (-50° to 220°F).
Principles of Operation (See Fig. 1)
The inlet pressure enters the space under the Diaphragm through
passage N. When the force created by the pressure exceeds the
force of the Range Spring, the Diaphragm is lifted off of the Pilot
Seat, allowing pressure to enter on top of the Power Piston.
This causes the Power Piston to move downward, forcing the
Modulating Plug to open and modulate to maintain constant inlet
pressure. (See pages 3 - 5 for principles of operation of other
A4W Variations.) An increase in inlet pressure lifts the Diaphragm
further, allowing more pressure on top of the Power Piston and
opening the valve wider. A decrease in inlet pressure causes the
Diaphragm to move closer to the Pilot Seat reducing the pressure
on the top of the Power Piston and allowing the Closing Spring to
reduce the valve opening.
The degree of valve opening is controlled by the amount of
pressure on top of the Power Piston, which in turn is controlled by
the fl ow through the Pilot Seat and the bleed off through the bleed
hole in the Power Piston to the outlet of the valve. The volume of
bleed fl ow from the top of the Piston to the valve outlet through
the clearance between the Power Piston and the piston bore is
very small because the Power Piston is fi tted with a Seal Ring.
Manual Opening Stem
All Type
A4W Regulators are provided with a Manual Opening
Stem
located at the top of the valve (refer to Fig. 1 for the location
of the stem and other related parts). For access to the stem
the Seal Cap on top of the regulator must be removed. Manual
opening is accomplished by turning the stem clockwise until only
the fl ats on the end of the stem protrude from the Packing Nut. To
reset for automatic operation, turn the stem counter-clockwise
as far as it goes.
CAUTIONS: 1.) The Seal Cap must be removed with care, as
refrigerant may have been trapped inside the cap. 2.) BEFORE
turning the stem, the Packing Nut should be loosened slightly,
and 3.) AFTER turning the stem, the Packing Nut should be
retightened. 4.) Always replace the Seal Cap when work with the
regulator is completed.
Adjustment
INLET PRESSURE REGULATORS - A4W
- (See Fig. 1) Install an
accurate pressure gauge in the gauge port. Back the Adjusting
Stem all of the way out to stop (counterclockwise). This will
reduce the set-point to its lowest level and will cause the valve to
OPEN wide. Start the system, and when the valve outlet pressure
is approaching the desired inlet pressure, turn the Adjusting
Stem in (clockwise) until the pressure gauge shows a slight
rise in inlet pressure. At this point the Adjusting Stem may be
turned in (clockwise) to raise the pressure further, or backed out
(counterclockwise) to lower it, but the fi nal adjustment should be
made after the system has been operating for a period of time and
has stabilized.
OUTLET PRESSURE REGULATORS - A4WOE
- (See Figs. 2,
2A) Install an accurate pressure gauge at the gauge port in the
A4WOE Adapter which is located next to the sensing tube that is
connected to the valve outlet line. Back the Adjusting Stem all of
the way out to stop (counterclockwise). This will reduce the set-
point to its lowest level and cause the valve to CLOSE. Operate the
system until the outlet pressure is lower than desired. Slowly turn
the adjusting stem in (clockwise) until the desired outlet pressure
is reached with the system stabilized.
PRESSURE SETTING RANGES
Inlet ranges available are A, V, and D
*Outlet pressure ranges available are V and D
Approx. Pressure Changes Factory Set Point
Set-Point Ranges per Turn of (unless otherwise
Adjusting Screw specifi ed)
A: 0 to 10.3 bar 1.7 bar (25 psi) 2.8 bar (40 psig)
(0 to 150 psig)
*V: 500mm hg to 8.3 bar 1.7 bar (25 psi) 1.0 bar (15 psig)
(20 in hg to 120 psig)
*D: 5.2 to 19.3 bar 3.7 bar (53 psi) 9.7 bar (140 psig)
(75 to 280 psig)
A Vacuum Range Regulator uses a Vacuum Cartridge instead of
the standard Pilot Seat 44. Except for this one difference, a “V”
Range Regulator is the same as an “A” Range Regulator as far
as the Range Spring 49 and Diaphragm Kits are concerned. (See
Figs. 7 and 8)
Type A4WE
(See Fig. 1)
Description
The Type A4WE is the same as a Type A4W except that the upstream
or remote pressure must be fi eld connected to the valve at the
gauge connection through an external line. (The external line is
not furnished with the regulator.) A Type A4W can be converted
to an A4WE by removing the adaptor from the body; remove the
alignment pin from passage ‘N’; and rotate the Gasket 5 to block
off the internal feed of upstream pressure. Re-assemble. (See
Fig. 7
)
Purpose
The Type A4WE is used when it is advantageous to use an external
source of upstream pressure to the regulator. Whatever the
source of pressure may be, it will be that pressure, as it exists
when it reaches the regulator, that will be controlled. There is a
small fl ow rate of fl uid through the external line and care must be
used to avoid a pressure drop by not under sizing the pipe or using
too long a length. Normally a US 3/8” pipe size not exceeding 6m
(20 ft.) in length will be adequate.
Fig. 2A - Outlet Pilot
Fig. 2
