TWO CONTACTS:
Close one contact upon an increase in pressure dif-
ference and close another upon a further increase.
PRESSURE CONNECTIONS
Connect HIGH Pressure source to REAR pressure connection and LOW
pressure source to FRONT pressure connection
(Fig. 5).
OPERATION-ADJUSTMENT
The two switch contacts are successively opened one after the other as
the pressure operating difference increases from the low differential
pressure setting to the high differential setting.
With both switches closed (low differential pressure) the REAR SWITCH
(9-81) will open as the pressure difference between the pressure cham-
bers increases (high side pressure increases or low side pressure
decreases). The FRONT SWITCH (9-83) will open as the pressure dif-
ference increases further to the high differential pressure setting. With
decreasing pressure differences the order of operation is reversed with
the FRONT SWITCH first to close the thereafter the REAR switch.
The change in pressure difference to reset each contact (sensitivity) is
not adjustable.
ADJUSTING SCREW “S”
changes the operating pressure difference for
the two switch contacts.
Turning knurled adjusting screw “S” Clockwise increases (widens) pres-
sure difference between the pressure chambers, necessary to open the
switch contacts. Turning screw “S” Counter-clockwise decreases (nar-
rows) the difference.
Adjustment screw “S” in increasing (widen) or decreasing (narrow) the
operating difference will, at the same time, establish the low operating
differential pressure setting for the REAR switch. If the rear switch is
open, turning screw “S” clockwise will close it.
ADJUSTMENT SCREW “D”
(small slotted screw located on magnet
arm) adjusts the spread between the pressure difference operating the
rear contact (low differential) and the difference to operate the front con-
tact (high differential).
Adjustment screw “D” in changing the spread between switch operations
will also establish the high operating differential pressure setting for the
FRONT switch. In using adjustment screw “D”, loosen locknut, adjust and
retighten nut. Turn “D” clockwise to increase (widen) spread and counter-
clockwise to decrease (narrow) spread.
OPERATING DIFFERENCES
when changed with adjustment “S” may
require readjustment for FRONT switch with adjustment “D”.
TWO CONTACTS:
Open one contact upon an increase in pres-
sure difference and open another upon a decrease in pressure
difference
PRESSURE CONNECTIONS
Connect HIGH pressure source to REAR pressure connection and LOW
pressure source to FRONT pressure connection
(Fig. 6).
OPERATION-ADJUSTMENT
With both mercury switch contacts closed (neutral zone) the FRONT
contact (9-83) will open as the pressure difference between chambers
increases (high side pressure rises, or low side pressure drops). As the
difference decreases, the FRONT contact will reclose.
When the pressure difference between the chambers decreases below
the neutral zone (high side pressure drops, or low side pressure rises)
the REAR contact (9-83) will open. As the difference increases, the
REAR contact will reclose.
The change in pressure difference to reset each contact (sensitivity) is
not adjustable.
ADJUSTMENT SCREW “S”
changes the operating differences for the
two switch contacts.
Turning knurled adjustment screw “S” clockwise increases (widens) the
operating difference between the pressure chambers necessary to open
the switch, contacts. Turning screw “S” counter-clockwise decreases
(narrows) the difference.
Adjustment “S” in increasing (widen) or decreasing (narrow) the operat-
ing difference will at the same time establish the low operating differen-
tial pressure setting for the rear switch. If the rear switch is open, turn-
ing screw “S” counter-clockwise will close it.
ADJUSTMENT SCREW “D”
(small slotted screw located on magnet
arm) adjusts the spread between the pressure difference operating the
REAR contact (low differential) and the difference to operate the
FRONT contact (high differential).
Adjustment “D” in changing the spread between switch operations will
also establish the high operating differential pressure setting for the
FRONT switch. In using adjustment “D” loosen lock-nut, adjust and
retighten nut. Turn screw “D” clockwise to increase (widen) spread and
counter-clockwise to decrease (narrow) spread.
OPERATING DIFFERENCES
when changed with adjustment screw “S”
may require readjustment for FRONT switch with adjustment “D”.
Mercoid® Diaphragm Differential Pressure Controls
Two Stage Types - Two SPST Magnetic Mercury
Switches Independently Adjustable
HIGH
PRESSURE
LOW
PRESSURE
DIAPHRA
GM
REAR
SWITCH
MAGNET
SCREW
"D"
FR
ONT
SWITCH
9 - 81
9 - 81
ADJUSTMENT
SCREW
"S"
Piping - Operating Characteristics - Adjustments
Specification - 4122
Types PPQ-PPQW-PPQE
HIGH
PRESSURE
LOW
PRESSURE
DIAPHRA
GM
9-81
REAR
SWITCH
MAGNET
SCREW
"D"
FR
ONT
SWITCH
9-83
ADJUSTMENT
SCREW
"S"
Fig. 5
Specification - 4123
Types PPQ-PPQW-PPQE
Fig. 6
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