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Adjustment
Install an accurate pressure gauge in the gauge port. Back the
adjusting stem all the way out to stop. This will reduce the set point to
its lowest level and cause the valve to open wide. Start the system,
and when suction pressure is about the desired pressure, turn the
adjusting stem in until the pressure gauge shows a slight rise in the
inlet pressure. At this point the adjusting stem may be turned in
(clockwise) to raise the pressure further, or backed out (counter-
clockwise) to lower it; but the final adjustment should be made after
the system has been operating for a period of time.
INLET PRESSURE SETTING RANGES
Approx. Pressure Change
Set Point Ranges
per Turn of
Adjusting Screw
A: 0 to 10.3 bar
1 .7 bar (25 psi)
(0 to 150 psig)
V: 500mm hg to 8.3 bar
1.7 bar (25 psi)
(20 in hg to 120 psig)
D: 5.2 to 19.3 bar
3.7 bar (53 psi)
(75 to 280 psig)
Type A4AZ (See Figs 1 and 2)
Description
The A4AZ Inlet Pressure Regulator is the basic building block from
which most Series A4 variations are made. This regulator incorporates
the specially designed Modudapter
Adaptomode
bolt on modules, providing unique modular construction
®
and many control valve variations with the use of a few modules and
kits. See page 3 for an explanation of "Basic Adaptomode Functions",
describing modules, module placement and schematic pilot circuit
flow diagrams for all variations covered within this bulletin.
The A4AZ regulator is a complete factory assembled and bench tested
valve and, in itself, may be used as a basic inlet pressure regulator. In
addition, this valve can easily be modified in the field to perform the
function of the A4AS, A4AB or A4AD valve variations.
Type A4AS (See Fig. 3)
Description
The Type A4AS 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 A4AS 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 as well as part of a temperature
control system.
Principles of Operation
The operation of the A4AS is the same as that described on page 1,
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 A4AS can begin to regulate
regardless of inlet pressure.
Adjustment
With the solenoid pilot electrically energized, proceed as described
above.
Type A4AB (See Fig. 4)
Description
The Type A4AB 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 i.e. not regulating. However, in the wide open
Refrigerating Specialties Division
Factory Set Point
(unless otherwise
specified)
2.8 bar (40 psig)
1 . 0 bar (15 psig)
9.7 bar (140 psig)
to accommodate the
®
2
mode the regulator will still require the 0.14 bar (2 psi) minimum
pressure drop. When the solenoid is de-energized the valve functions
as an Inlet Pressure Regulator.
Purpose
The Type A4AB frequently is used with the wide-open function where
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.
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 drop to a
lower level. Frequently this regulator is used in the wide open mode
for evaporator pump out prior to hot gas defrost.
Principles of Operation
The operation of the A4AB is the same as that described on page 1
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 where, 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.
Type A4AD (See Fig. 5)
Description
The Type A4AD is a Dual Inlet Pressure Regulator capable of regulating
at two different pressure set-points. When the integrally mounted S6A
Pilot Solenoid Valve is energized the regulator is controlling at the
lower of 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 at the higher set-point, which must be
adjusted on the bolt-on (outboard) pressure pilot.
Purpose
The Type A4AD uses are similar to those for the A4AB except, 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, and evaporator pressure
control combined with defrost pressure relief.
Principles of Operation
The operation of the A4AD is similar to that described on page 1.
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 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 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. Energize the solenoid
pilot and adjust the integral pressure pilot for the desired low pressure
setting following the adjusting procedure described above.
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