Honeywell HP970A Mounting instructions

Honeywell
HP970A, B and HP972B
Pneumatic Humidistats
SERVICE DATA
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, HP972BI 013, has all the
necessary adapter fittings to convert older models or
competitors’ humidistats” Figure
1 shows a typical HP970A,
13, or HP972B two-pipe hookup. Figure 2 shows a typical
HP972B one-pipe hookup.
HP970A, B
HP972B
MB
VALVE
SUPPLY
N.C.
C322.5
Fig. 1. Typical HP970A, 6or HP972B Humidistat
Two-Pipe Hookup.
HP972B
RESTRICTION
(BLUE) HUMIDIFIER
VALVE
~
N.C.
SUPPLY
C3226
Fig. 2. Typical HP972B Humidistat One-Pipe Hookup.
SPECIFICATIONS
Action:
HP970A: Direct Acting
HP970B: Reverse Acting
HP972B: Reverse Acting
Means of Adjustment:
External knob with internally adjustable setpoint locking stops
for minimum and maximum settings
Maximum Safe Pressure:
25 psi (172 kPa)
Supply Air Pressure:
13 to 21 psi (90 to 145 kPa)
18 psi (124 kPa) nominal
Copyright 0 1989 Honeywell Inc. 0 All Rights Reserved
75-7195
Branchline Pressure Indication:
Self-sealing gage tap under the cover

Ht=‘97OA, B AND HP9728 PNEUMATIC HUMlDlSTATS
CLEA
HP97CV4, B: Adjustable TR factory set at 5% rh
3 to 15% rh Low Range
3 to 20% rh High Range
0
HP972B:
Adjustable TR factory set at 12% rh
7 to 35% rh Low Range
If the Humidistat is in an area where it is exposed to
dust or dirt, periodicaliy remove the cover and use an
air hose or soft brush to remove accumulated dust or
dir-t.
Ambient Operating: 45 to 125F (7 to 516)
Storage: -30 to l5OF (-35 to EC)
1972
HP970A and B sense changes in ambient relative humidity.
The sensed change causes a proportional change in the
branchline pressure (BLP) and changes the control actuator
position by the same proportion. The
HP970A (DA) increases
and the HP9708 (RA) decreases the BLP when the relative
humidity increases.
The
WP972B (RA) provides an inverse branch pressure
signal in relation to the sensed relative humidity. The wide
throttling range allows a reset of
reilative humidity as a
function of the outdoor temperature, preventing condensation
during extreme winter conditions.
The tools shown in Figure 3 and a sling psychrometer or
Digital Relative Humidity Pen
CCT915 are necessary to
calibrate the Humidistats.
PEN CCT915
0
if the nylon sensing element becomes contaminated
with oil, grease, or dust, remove and clean it by meetly
agitating it in an acetone solution. Dry the element at
room temperature.
Re~~sta~~ the efement and recalibrate
the Humidistat.
The throttling range is factory set and should not
r~~~~re any
change under normal operating conditions. If a change in
relative humidity causes the system to hunt or the response is
too slow, reset the throttling range as follows:
If the system hunts or the controlled device cycles,
move the throttling range indicator down. If the
response is too slow, move the throttling range ifldicator
up toward minimum.
@ Recalibrate the Humidistat each time the throttling
range is changed.
THROTTLING
INDICATOR
CALIBRATIO
NYLON
LEMENT
LOCK SCREW
SE-i-POINT/
-----SETPOINT
LOCKING STOPS ADJUSTMENT
6301-3
Fig. 4. Humidistat with t
djust
ig. 3. Calibration Tools.
75-7195

HP970A, 5 AND HP9725 PNEUMATIC HUMID/STATS
SETPOINT LOCK ADJUSTMENT
Set the minimum and maximum setpoint as follows:
0 Loosen the setpoint lock screw (Fig. 4).
@ Move the setpoint locking stops to the desired position.
0 Tighten the setpoint lock screw.
@ Check the stop positioning by turning the setpoint
adjustment.
CALIBRATION CHECK
HP97OA
Measure the rh with an accurate rh measuring device.
Turn the setpoint adjustment until the setpoint indicator
reads IO percent below the indicated rh and allow the
Humidistat to build up BLP.
Turn the setpoint indicator up slowly using the setpoint
adjustment.
if the Humidistat bleeds off at 13 percent rh of the
indicated humidity, no further calibration is necessary. If
the Humidistat does not bleed off properly, proceed with
RECALIBRATION.
HP970B and HP972B
Measure the rh with an accurate rh measuring device.
Turn the setpoint adjustment until the setpoint indicator
reads 10 percent above the indicated rh and allow the
Humidistat to build up BLP.
Turn the setpoint indicator down slowly using the
setpoint adjustment.
If the Humidistat bleeds off at &3 percent rh of the
indicated humidity, no further calibration is necessary. If
the Humidistat does not bleed off properly, proceed with
RECALIBRATION.
RECALIBRATION
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
is off.
Ensure the system is stabilized and the main air is
maintained at normal pressure between 13 and 21
psi (90 and 145
kPa). Factory calibration is 18 psi
(125 kPa).
Remove the Humidistat cover.
Install the Pressure Gage into the gage tap (Fig. 4)
using the Gage Adapter.
Measure the rh with an accurate rh measuring device.
Use the setpoint adjustment to set the setpoint
indicator at the actual relative humidity.
Adjust the calibration screw (Fig. 4) until the Pressure
Gage reads 0 psi (0
kPa).
Readjust the calibration screw slowly until the
Pressure Gage reads 8
+I psi (55 f7 kPa).
Allow sufficient time for a complete response and
stabilization, then recheck pressure. The Humidistat
is now calibrated.
Remove the Pressure Gage and Gage Adapter.
NOTE: If the gage tap fails to seal itself properly
after the Pressure Gage is removed, bleed
off a small amount of air and insert Gage
Tap Plug 14002172-001 into the gage tap.
Replace the Humidistat cover.
Set the Humidistat at the desired setting.
TROUBLESHOOTING
Table 1 lists common Humidistat problems, their possible
causes, and solutions. For any problems not covered in Table
2, Troubleshooting Flowchart (Fig. 5).
75-7195

HP97QA, i!? AND HP9725 PNEUMATIC HUMIDISTATS
Table 1. Common Problems, Causes, and Solutions.
75-7195

HP970A, BAND HP972B PNEUMATIC HUMIDISTATS
RESSURE ISREDUCE
1 NOZZLE ~SEMBLY./
f
CHECKTHE MAIN AIR
PRESSURE AT THE PRV
PRESSURE DROP
IN THE LONG AIR
Fig. 5. Humidistat Troubleshooting Flowchart.
75-7195

HP970A, BAND HP972B PNEUMATIC HUIWDISTATS
REPAIR
SCALEPLATE REPLACEMENT
GENERAL
If the Humidistat requires replacement, do not remove the
existing mounting plate from the mounting surface, or adjust
or repair any piping.
HUMDISTAT REPLACEMENT
Remove the Humidistat cover.
Insert a small screwdriver blade between the setpoint
indicator and the scaleplate assembly (Fig. 7) and pry
the setpoint indicator up off the
setpoint cam and
wheel assembly.
Carefully pry off the two retaining rings from the
scaleplate mounting posts.
Detach the scaleplate locking tab at the right of the
Humidistat base and lift off the scaleplate assembly.
Using the retaining rings included with the new
scaleplate assembly, install the new scaleplate in
reverse order. Be certain to align the flat of the setpoint
pointer with the flat on the hub of the setpoint cam and
wheel assembly.
Check calibration of Humidistat and recalibrate if
necessary.
Remove the Humidistat cover.
Remove the old Humidistat, leaving the airhead
connected to the mounting plate.
Discard the new mounting plate.
Align the port holes (Fig. 6) on the back of the
replacement Humidistat with the air connections on the
existing airhead.
Snap the new Humidistat onto the old mounting plate.
Calibrate the new Humidistat.
Reinstall the Humidistat cover.
NOTE: If the gage tap fails to seal itself properly after
Pressure Gage 14003519-001 is removed, bleed off
a small amount of air and insert Gage Tap Plug
14002172-001 into the gage tap.
Reinstall the Humidistat cover.
PORT
BACK PLATE
MOUNTING
SCREWS (4)
TO CHANGE
FILTER REM
BACK
MULTI STAGE
CARTRIDGE
TYPE FILTER
(UNDER BACK
PLATE)
SCALEPLATE
RETAINING
RINGS (2)
INDICATOR
SCALEPLATE SCALEPLATE
LOCKING TAB
ENGAGEMENT
SLOI
SETPOINT CAM AND
WHEEL ASSEMBLY
FEg. 6. Humidistat Back View. Fig. 7.
Scalepiate Replacement.
75-7195
6

HP970A, B AND HP9725 PNEUMATIC HUMIDISTATS
SETPOINT CAM ASSEMBLY REPLACEMENT
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.
CALIBRATION LEVER ARM7
RELIEF SPRING
SPRING POST
Fig. 8. Back of the Humidistat Showing Relief Spring
Connections.
SCREW \
__
CALIBRATION
CALIBRATION
LEVER
HOOK
rMOUNTING SCREW
(NO. 4 x
3/16 PN HD)
NOZZLE/FLAPPER
ELEMENT
CALIBRATIO
ELEMENT
LEVEL
HOOK
ASSEMBLY
YOKE
CALI BRATION
LEVER ---!i
6305-3
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
REPLACEMENT-
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.
LEVER 6304-2
Fig. 9. Humidistat with Scaleplate Removed Showing
Setpoint Cam Assembly.
75-7195

HP97OA, BAND HP972B PRISMATIC HUMIDISTATS
TYPICAL
PNEUMATIC
/ASSEMBLY
Follow steps 1 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.
Lift the nozzle/flapper assembly from the base.
Remove the O-ring from the rear of the nozzle/flapper
assembly.
Disengage the other end of the bias spring from the
bracket hole. Do not lose the small pin located inside
the spring.
Assemble the O-ring and the bias spring to the
replacement nozzle/flapper assembly and reinstall in
reverse order.
Recalibrate the humidistat.
FILTER CARTRIDGE
RESTRICTOR
Reinstall the tiumidistat cover.
SEMBLY AND
LACEMENT
MOUNTING +
SCREWS (4)
When replacing these parts, use extreme care to
prevent dirt, dust, or debris from entering various
openings of the Humidistat base or the restrictor
block.
Remove the humidistat cover.
Remove the Humidistat.
3*
6333-2
Fig. Il. Restrictor Block Assembly and Filter
Cartidge Replacement.
Access to the restrictor block assembly and filter
cartridge is from the rear of the base assembly.
Remove the four mounting screws from the restrictor
block (Fig.
71).
Carefully lift off the restrictor block (Fig. 11).
Remove the flat rubber gasket from the restrictor
block. The filter cartridge is located in the gasket.
Remove the filter cartridge from the gasket.
Align the gasket on the base assembly, and insert the
new filter cartridge into the recess in the base with the
screen end of the filter exposed.
Place the new restrictor block over the hasket and
filter
cartidge, and replace the four mounting screws.
Snap the humidistat onto the mounting pfate.
Recalibrate the humidistats
Reinstall the humidistat cover.
75-n 9.5

HP97OA, 5 AND HP9725 PNEUMATIC HUMIDISTATS
PARTS AND AC
PARTS LIST
Table 2. HP970A, B and HP972B Pneumatic Humidistat Parts List.
Part No. Description
Scafeplate Assembly, Blank
14002641-001
Scaleplate Assembly, 15 to 75 percent
1 14002641-002 Scaleplate Assembly, 65 to 95 percent
I
14002594-001 Setpoint Cam Assembly
14002496-001
Element Assembly, HP970A, HP970B1007
14002496-003 Element Assembly, HP970BlOi 5, HP972B
I4001 865-001 Filter Cartridge Assembly
COVERS
Table 3.HP970 Series Pneumatic Humidistat Covers.
Part Number Suffix*
Window insert
Setpoint
-
20-80
(% RH)
o Window Insert
?03040506070(
Vhen ordermg, use completepart number rncludrng three-digrt suttrx.
14004407-XXX Covers are paintable. See HP970-72 and TP970-74 Pneumatic Sensors, Humidistats,
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
14002430-001 Heavy Duty Guard
14002573-001 Modernization Kit
14003-l 92-001 Wall Plate Adapter Kit
AK3996C Duct MountingBracket
14002 172-001 Gage Tap Plug
Pressure Gage
MQP729 (CCT729)
Gage Adapter
MQT735A (CCT735A)
1 Thermostat Tool
75-7195

Honeywell
Home and Building Control Home and Building Control
Honeywell Inc. Honeywell Limited-Honeywell
Limitie
Honeywell Plaza 740 Ellesmere Road
P.O. Box 524 Scarborough, Ontario
Minneapolis, MN 55408-0524
MlP 2V9
Helping You Control Your World
75-7195 8-89
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