Refrigerating Specialties Division
4
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, regard-
less 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.
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 bypass-
ing 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 de-
energized, 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 evapo-
rator is required for some period of time. With the solenoid de-
energized, 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 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 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
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 set-
points. This would be the electrically compensated low pres-
sure pilot doing the controlling. When the pilot solenoid is de-
energized 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.
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 evapo-
rator 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 modu-
lar (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 dia-
phragm 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.
