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The HP97OA, B and HP972B Pneumatic Humidistats
(Humidistats) are nylon element, proportional, two-pipe,
devices used to control humidity in HVAC systems.
The HP970A and B Pneumatic Humidistats control pneumatic
valve and damper actuators in air conditioning systems
requiring humidification and/or dehumidification.
The HP972B is used in systems requiring a reset of relative
humidity as a function of outdoor air temperature, wide
throttling range, or replacement of existing one-pipe
humidistats" A special
model,
necessary adapter fittings to convert older models or
competitors' humidistats" Figure 1 shows a typical HP970A,
Copyright 0 1989 Honeywell Inc. 0 All Rights Reserved
HP970A, B and HP972B
Pneumatic Humidistats
Fig. 1. Typical HP970A, 6 or HP972B Humidistat
Two-Pipe Hookup.
RESTRICTION
(BLUE)
Fig. 2. Typical HP972B Humidistat One-Pipe Hookup.
SPECIFICATIONS
Action:
Means of Adjustment:
External knob with internally adjustable setpoint locking stops
for minimum and maximum settings
Maximum Safe Pressure:
25 psi
Supply Air Pressure:
13 to 21 psi (90 to 145 kPa)
18 psi (124 kPa) nominal
Branchline Pressure Indication:
Self-sealing gage tap under the cover
Honeywell
SERVICE DATA
MB
VALVE
N.C.
SUPPLY
HUMIDIFIER
VALVE
N.C.
SUPPLY
C3226
75-7195
Related Manuals for Honeywell HP970A
Summary of Contents for Honeywell HP970A
- Page 1 Honeywell HP970A, B and HP972B Pneumatic Humidistats SERVICE DATA VALVE N.C. SUPPLY Fig. 1. Typical HP970A, 6 or HP972B Humidistat Two-Pipe Hookup. RESTRICTION HUMIDIFIER (BLUE) VALVE N.C. SUPPLY C3226 The HP97OA, B and HP972B Pneumatic Humidistats Fig. 2. Typical HP972B Humidistat One-Pipe Hookup.
- Page 2 (BLP) and changes the control actuator position by the same proportion. The HP970A (DA) increases If the system hunts or the controlled device cycles, and the HP9708 (RA) decreases the BLP when the relative move the throttling range indicator down.
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Page 3: Troubleshooting
RECALIBRATION Set the minimum and maximum setpoint as follows: CAUTION These Humidistats are sensitive devices and should be handled with extreme care during calibration. Do not breathe directly on the element when the cover adjustment. is off. CALIBRATION CHECK Ensure the system is stabilized and the main air is maintained at normal pressure between 13 and 21 psi (90 and 145 kPa). - Page 4 Table 1. Common Problems, Causes, and Solutions.
- Page 5 HP970A, BAND HP972B PNEUMATIC HUMIDISTATS PRESSURE AT THE PRV PRESSURE DROP IN THE LONG AIR RESSURE IS REDUCE N O Z Z L E Fig. 5. Humidistat Troubleshooting Flowchart.
- Page 6 HP970A, BAND HP972B PNEUMATIC HUIWDISTATS SCALEPLATE REPLACEMENT REPAIR Remove the Humidistat cover. GENERAL Insert a small screwdriver blade between the setpoint indicator and the scaleplate assembly (Fig. 7) and pry the Humidistat requires replacement, do not remove the the setpoint indicator up off the setpoint cam and existing mounting plate from the mounting surface, or adjust wheel assembly.
- Page 7 HP970A,B AND HP9725 PNEUMATIC HUMIDISTATS MOUNTING SCREW (NO. 4 x 3/16 PN HD) Follow Steps 1 through 4 of SCALEPLATE REPLACEMENT. Disconnect the relief spring (Fig. 8) from the calibration N O Z Z L E / F L A P P E R lever arm on the back of the Humidistat.
- Page 8 TYPICAL PNEUMATIC / A S S E M B L Y Follow steps through 4 of SCALEPLATE Unhook the coil spring of the element assembly from the nozzle/flapp~r assembly bracket (Fig. IO). Unhook the bias spring from its anchor post. Remove the frame post and mounting screw.
- Page 9 Window Insert 20-80 Vhen ordermg, use complete part number rncludrng three-digrt suttrx. and Thermostats Installation instructions 955597 for painting information. ACCESSORIES Table 4. HP970A, B and HP9728 Pneumatic Humidistat Accessories Parts List. Part No. Description 14002362-001 Duct Sampling Chamber...
- Page 10 By using this Honeywell literature, you agree that Honeywell will have no liability for any damages arising out of your use or modification to, the literature. You will defend and indemnify Honeywell, its affiliates and subsidiaries, from and against any liability, cost, or damages, including attorneys’ fees, arising out of, or resulting from, any modification to the Honeywell literature by you.