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Follow Steps 1 through 4 of SCALEPLATE
REPLACEMENT.
Disconnect the relief spring (Fig. 8) from the calibration
lever arm on the back of the Humidistat.
Carefully unhook the element assembly yoke (Fig. 9
and IO) from the hook of the calibration lever, located
immediately above and to the right of the setpoint
wheel.
Swing the element assembly (Fig. IO) up and to the
right. It is not necessary to disengage the element
assembly coil spring from the nylon element or nozzle
and flapper assembly bracket.
Remove the pivot post (Fig. 9) at the left of the setpoint
wheel, the setpoint lever, and the calibration lever. Do
not lose the spacer positioned between the base and
the calibration lever.
Lift out the old setpoint cam and wheel assembly and
install the replacement unit in reverse order. Make
certain that the two levers are free to move.
Recalibrate the Humidistat.
Reinstall the Humidistat cover.
RELIEF SPRING
SPRING POST
Fig. 8. Back of the Humidistat Showing Relief Spring
Connections.
SCREW \
CALIBRATION
LEVER
Fig. 9. Humidistat with Scaleplate Removed Showing
CALIBRATION LEVER ARM7
__
CALIBRATI
N
O
LEVER
H O O
K
HP970A,B AND HP9725 PNEUMATIC HUMIDISTATS
r
MOUNTING SCREW
(NO. 4 x 3/16 PN HD)
L E V E L
H O O K
L E V E R ---!i
Fig. IO. Humidistat with Scaleplate and Setpoint Cam
Assembly Removed Showing Element Assembly and
Nozzle/Flapper Assembly.
ELEMENT ASSEMBLY REPLACEMENT
Follow steps 1 through 4 of SCALEPLATE
Unhook the coil spring of the element assembly bracket
(Fig. IO}.
Disengage the element assembly yoke from the
calibration lever hook located directly above the setpoint
wheel.
Remove element assembly and install replacement unit
in reverse order.
Recalibrate the Humidistat.
Reinstall the Humidistat cover.
N O Z Z L E / F L A P P E R
ELEMENT
ELEMENT
ASSEMBLY
YOKE
75-7195
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