Refrigerating Specialties Division
8
A4AB INLET PRESSURE REGULATOR WITH
ELECTRIC WIDE-OPENING VARIATION
The A4AB Pressure Regulator controls the inlet
(evaporator) pressure when the solenoid pilot is de-
energized and opens wide when the solenoid pilot is
electrically energized regardless of the regulator setting.
The S6A Modular Solenoid Pilot (Fig. 12) is mounted on
Pad 2 of the Modudapter and the Moduplate (Fig. 11) is
mounted on Pad 1 with the “B” side exposed. The
Moduplate acts to channel the flow from Path X to Path
Y. See Modudapter flow paths on page 7.
Operation-When the solenoid pilot is de-energized the
operation is similar to A4A. The inlet pressure is
transmitted through Passage N to Path X and through
the Moduplate to Path Y. Path Y transmits the pressure
to the underside of the diaphragm (see Fig. 16) and the
pilot will operate as described for A4A (see page 4). When
the solenoid pilot is electrically energized the pressure
is transmitted through Path X to the solenoid pilot and
through the open solenoid pilot to Path Z. Path Z transmits
the pressure directly to the top of the piston causing it to
open the throttling plug, allowing flow through the
regulator (see Fig. 15).
Adjustment-With the solenoid pilot de-energized,
proceed as with the A4A. (See page 4.)
A4AD DUAL INLET PRESSURE REGULATOR
The A4AD Pressure Regulator controls the inlet (evaporator) pressure
at either of two pre-set pressures. When the solenoid pilot is energized,
the A4AD controls at the lower pressure setting; when it is de-energized,
the regulator controls at the higher pressure setting.
The S6A Modular Solenoid Pilot (Fig. 12) is mounted on Pad 1 of the
Modudapter; the A2D Modular Pressure Pilot (Fig. 10) is mounted on
Pad 2.
The 20 to 32 mm (3/4" to 1-1/4") A4AD Regulator gauge connections
require the addition of a 1/4" NPT nipple and coupling to make a 50
mm (2") extension to allow installation of a gauge valve or gauge.
Operation - When the solenoid pilot is de-energized, the Path Y is
closed off from Path X and the inlet pressure from Passage N cannot
enter the space under the diaphragm of the integral (low pressure)
pilot. The inlet pressure is transmitted to the space under the diaphragm
of the modular pressure pilot (high pressure) through Path X, and the
pilot operates as described for A4A (see page 4). The pressure is
transmitted to the top of the piston through Path Z (see Fig. 18) and the
regulator operates like an A4A. See Modudapter flow paths on page 7.
When the solenoid pilot is electrically energized, the inlet pressure from
Passage N is transmitted through Path X through the open solenoid
pilot to Path Y. Path Y transmits the pressure under the diaphragm of
the integral pressure pilot (low pressure) which will operate the regulator
like an A4A (see Fig. 17). The modular pressure pilot is inactive because
of its higher pressure setting. Note: On the older A4CD design the pilot
locations were reversed, the integral pilot was the high pressure pilot.
Adjustment-De-energize the solenoid pilot and adjust the modular
pressure pilot for the desired high pressure setting following the A4A
adjusting procedure (see page 4). Energize the solenoid pilot and adjust
the integral pressure pilot for the desired low pressure setting following
the A4A adjusting procedure (see page 4).
