Refrigerating Specialties Division
3
The pressure as measured at the connection to the valve must be
no less than the pressure at the valve inlet.
A 13mm (1/2”) Type RSF strainer can be installed in the above line
to protect the critical pilot circuit of the main valve and eliminate
the space required for and the cost of a full line-size strainer.
If this is done, it should be remembered that any pressure drop
in this line caused by an overloaded strainer basket will affect
the actual pressure at which the regulator will control. If this is
the case, then the actual pressure at the main valve inlet will be
higher than it should be by an amount equal to the pressure drop
through the pilot circuit strainer.
Principles of Operation
The operation of the Type A4WE is the same as that described
above for the A4W except that the upstream pressure being
controlled is fed to the valve externally.
Adjustment
Follow the instructions above for the Type A4W Regulator.
Type A4WS
(See Fig. 3)
Description
The Type A4WS is an 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 A4WS should be used where it is required at particular
times to stop all fl ow through the regulator. The valve, however, is
NOT a check valve and cannot prevent reverse fl ow of fl uid if the
outlet pressure exceeds the inlet pressure by more than 0.14 bar
(2.0 psi). Typical uses include defrost applications as well as part
of a temperature control system.
Principles of Operation
The operation of the A4WS is the same as that described for the
A4W on page 2, except the inlet pressure from passage N must
pass through the S6A Pilot Solenoid Valve before it can reach the
diaphragm. Thus, the S6A Pilot Solenoid must be energized before
the A4WS can begin to regulate, regardless of inlet pressure.
Adjustment
With the solenoid pilot electrically energized, proceed as
described above for Inlet Pressure Regulators.
Type A4WB
(See Fig. 4)
Description
The Type A4WB is an Inlet Pressure Regulator with a Pilot Electric
Wide-opening, or Bypass, variation. When the integrally mounted
solenoid is energized the main valve is wide open thereby
bypassing the regulator function, that is, not regulating. However,
in the wide open mode the regulator will still require the 0.14 bar
(2 psi) minimum pressure difference to be fully open. When the
solenoid is de-energized the valve functions as an inlet pressure
regulator.
Purpose
The Type A4WB frequently is used in the wide-open mode when
maximum refrigeration capacity from an evaporator is required.
During the defrost of the evaporator, the regulator pilot solenoid
is de-energized, thus functioning as a defrost relief regulator or
for high pressure limit protection. Also, this regulator can be used
in the wide open mode for evaporator pump out prior to defrost.
When used in a discharge pressure line, it can, when de-energized,
hold back enough pressure for some heat reclaim or defrosting
function and then, when energized, allow the discharge pressure
to decrease to a lower level.
Principles of Operation
The operation of the A4WB is the same as that described for the
A4W on page 2, when operating as a regulator (Pilot Solenoid De-
energized). 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, whereby, provided a 0.14
bar (2 psi) pressure difference exists across the main valve, the
Modulating Plug will be held wide open.
Adjustment
With the solenoid pilot electrically de-energized, proceed as
described above for Inlet Pressure Regulators.
Type A4WD (See Fig. 5)
Description
The Type A4WD is a Dual Inlet Pressure Regulator capable
of regulating two different pressure set-points. When the
integrally mounted S6A Pilot Solenoid is energized, the regulator
is controlling the lower of the two set-points, which must be
adjusted on the pressure pilot over the center of the main valve.
When the solenoid is de-energized, the regulator is controlling
the higher of the two set-points, which must be adjusted on the
bolt-on (outboard) pressure pilot.
Purpose
The Type A4WD uses are similar to those for the A4WB except
that, instead of operating in a wide-open position when the pilot
solenoid is energized, the regulator is controlling at some preset
level.
Typical uses include capacity control of an evaporator at two
different pressure levels to regulate temperature, or evaporator
pressure control combined with defrost or wash down pressure
relief.
Principles of Operation
The operation of the A4WD is similar to that described for the
A4W on page 2. When the Pilot Solenoid is energized, upstream
pressure from passage N is made available to both diaphragms.
Since the path of least resistance will be through the pilot having
the lower set-point (lower range spring force), that pilot will
control.
When the Pilot Solenoid is de-energized, the upstream pressure
from passage N can fl ow only to the high pressure pilot, which will
then control the regulator.
Adjustment
Electrically de-energize the solenoid pilot and adjust the modular
(bolt-on) pressure pilot for the desired high pressure setting
following the adjusting procedure as described above.
Fig. 4 - A4WB
Fig. 3 - A4WS
