Honeywell H8908D, H8908C, H8908B, H8908A User Manual

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H8908A/B Humidistat;

CAUTION

H8908C/D Dehumidistat

INSTALLATION INSTRUCTIONS

APPLICATION

The H8908 family of low-voltage humidistats/ dehumidistats provide accurate control of whole house humidifiers, dehumidifiers, and ventilators. They have a snap-acting, dust-proof SPST switch and can be mounted to a duct or wall.

Before Installing this Product...

1. Read these instructions carefully. Failure to follow

them could damage the product or cause a hazardous condition.

2. Check the ratings given in the instructions and on

the product to make sure the product is suitable for your application.

3. Installer must be a trained, experienced service

technician.

Fig. 1. H8908A,D control.

M24726

Personal Injury Hazard. Power supply can cause electrical shock.

Disconnect power supply before beginning installation.

NOTE: The H8908 electrical connections are not

shared with the thermostat.

OUTDOOR

TEMPERATURE

-20 F

-30 C

-10 F

Humidity Control Régulateur d'humidité

HOLE FOR WIRING THE DUCT MOUNTING INSTALLATIONS

0 F +10 F +20 F

Over 20 F

Over 0 C

CASE REMOVAL SLOT

-25 C

-20 C

-10 C

-5 C

Fig. 2. H8908B,C control.

HUMIDITY SETTING

15%

20% 25% 30%

35% 40%

M13371

69-1341EF-07

H8908A/B HUMIDISTAT; H8908C/D DEHUMIDISTAT

DUCT INSTALLATION

1. Choose a location on the duct.

ALTERNATE LOCATION

RETURN AIR

6 in. (152 mm) MINIMUM

BEST LOCATION

RETURN AIR DUCT

15 in. (381 mm) MINIMUM

Fig. 3. Duct installation locations.

2. Apply sticker template to duct and drill holes for

mounting screws. Cut along the dotted line of the template with metal shears or tin snips.

Fig. 4. Drill and cut holes in duct.

3. Run two-fan, low-voltage wire to the mounting loca-

tion on the duct. See Fig. 5.

IMPORTANT

Use rated 18-22 gauge wire. Leave approximately 6 in. of wire to properly connect the humidistat.

RETURN AIR

M13369

M24800

REMOTE MOUNT INSTALLATION

1. Choose a location in the living area.

NOTE: Select a location clear of drafts or excessive

humidity. Avoid mounting near doors or windows, or in bathrooms or kitchens. See Fig. 6.

Fig. 6. Choose a location in the living area.

2. Cut 1 in. diameter wire hole in wall.

3. Run two-fan, low-voltage wire to the mounting loca-

tion in the living area.

IMPORTANT

Use rated 18-22 gauge wire. Leave approximately 6 in. of wire to properly connect the humidistat.

M24718

RETURN

SUPPLY

TWO-FAN 18-22 GAUGE WIRE

M24720

Fig. 5. Run wire to the mounting location.

69-1341EF—07 2

M24721

Fig. 7. Run wire to the mounting location.

H8908A/B HUMIDISTAT; H8908C/D DEHUMIDISTAT

M24722

4. Remove the base bracket from the humidistat. For

duct mount, slide the black gasket onto the base bracket. See Fig. 8.

NOTE: Use gasket only when mounting the control to

ductwork. Leave off when mounting to a wall.

M24733

Fig. 8. Seal base bracket.

5. Secure the base bracket to the duct or remote loca-

tion. Secure to the duct with four 1-in. (25 mm) screws (provided) or to the wall with two 1-in. (25 mm) screws (provided).

Fig. 9. Mount base bracket to duct or remote location.

3 69-1341EF—07

H8908A/B HUMIDISTAT; H8908C/D DEHUMIDISTAT

CAUTION

WIRING

Personal Injury Hazard. Can cause electrical shock and injury.

Disconnect power before installation or servicing.

All wiring must comply with applicable local codes, ordinances and regulations. Make wiring connections according to humidifier (or dehumidifier/ventilator) instructions, if available; otherwise, see typical wiring diagrams in Fig. 12–19.

IMPORTANT

Select models of fan centers include humidifier taps so the current sensing relay, sail switch or air pressure switch is not needed. If not using a current sensing relay, sail switch, or air pressure switch, the humidifier must be energized during blower motor cycles for proper operation.

On multispeed blower applications, do not wire the high voltage side of the transformer to the same power source that services the furnace blower. Premature transformer burnout can occur. On HE365 fan powered humidifier models, only the two yellow wires are connected to the control. The remaining two red wires are only used with electronic humidity controls.

6. Using wire nuts, connect the low-voltage wire to the

leads on the H8908 humidistat. See Fig. 6–19 for different wiring configurations.

H8908

30 40

TRANSFORMER

OFF ON

HUMIDIFIER

POWER

(HOT)

12PROVIDE DISCONNECT MEANS AND

FAN CONTROL

SUPPLY

FURNACE FAN MOTOR

OVERLOAD PROTECTION AS REQUIRED.

24 VAC WIRING.

Fig. 12. Wiring H8908 with fan interlock.

POWER

(HOT)

SUPPLY

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

24 VAC WIRING.

FAN CONTROL

DPST SWITCHING RELAY

2-SPEED FAN MOTOR

TRANSFORMER

Fig. 13. Wiring H8908 with 2-speed fan motor.

H8908

30 40

OFF ON

HUMIDIFIER

M24728

M24727

M24734

Fig. 10. Wire the humidistat.

7. Mount the humidistat by hooking the two hinges at

the top of the back cover to the raised edge at the top of the base bracket. Press the bottom of the humidistat in to engage the base hinge. You will hear a “click” when the humidistat is secured.

M24801

Fig. 11. Attach the humidistat to the base.

69-1341EF—07 4

H8908

30 40

OFF ON

TRANSFORMER

CURRENT SENSING RELAY

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

24V WIRING.

Fig. 14. Typical wiring diagram of current

sensing relay with humidifier.

(HOT)

HUMIDIFIER

WATER SOLENOID LEAD WIRE

M24729

H8908A/B HUMIDISTAT; H8908C/D DEHUMIDISTAT

H8908

AIR

PRESSURE SWITCH/

SAIL SWITCH

OFF ON

TRANSFORMER

(HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

24V WIRING.

Fig. 15. Wiring H8908 in line with

air pressure switch/sail switch and humidifier.

TH9421 VISION PRO

THERMOSTAT

H8908B

30 40

OFF ON

24 VOLT

TRANSFORMER

HUMIDIFIER

1 2 3

SYSTEM

TRANSFORMER

M24730B

COM N.O. N.C.

S688 AIR

PRESSURE

SWITCH/

SAIL SWITCH

HE225/HE265

HUMIDIFIER

Fig. 17. Wiring H8908 with VisionPRO® IAQ on typical 2-stage furnace.

VISIONPRO® THERMOSTAT

Y2 L A W2 S1 S2

H8908D

H8908

FAN WIRING

30 40

TERMINALS

OFF ON

HUMIDISTAT TERMINALS

24V WIRING.

FOLLOW THE INSTALLATION INSTRUCTIONS

NOTE:

INCLUDED WITH THE STEAM HUMIDIFIER TO WIRE THE SYSTEM FAN.

HUMIDIFIER

Fig. 16. Wiring H8908 with steam humidifiers.

EQUIPMENT INTERFACE MODULE

1 2 3 C

24 VAC

R RC RH

H1 U M2

D1 H

M2 V1

N T2

H8908D

30 40

OFF ON

CONV. HP

W1 W2 W3 Y Y2 G

L NOT USED OUT1 OUT2 IN1 IN2

DATS1

DATS2

STAGE 1

O/B AUX AUX2 Y Y2 G

HEAT

STAGE 2 HEAT

COMPRESSOR

FAN RELAY

C7089U1006

VENTILATOR/DEHUMIDIFIER

TERMINALS

TO SYSTEM FAN

M24731

M24724B

HEATING RELAY OR VALVE COIL

COOLING CONTACTOR COIL

FAN RELAY COIL

PROVIDE OVERLOAD PROTECTION

AND DISCONNECT MEANS AS REQUIRED.

Fig. 18. Wiring H8908 with VisionPRO®

Thermostat for dehumidification.

30 40

OFF ON

M24725

Fresh Air Ventilation System Système de ventilation à air frais

Fig. 19. Typical wiring diagram for HR150,

HR200, ER150 and ER200 Ventilator

or DH90 Dehumidifier applications.

M24732

5 69-1341EF—07

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