Honeywell Home H8908A/B Humidistat, H8908C/D Dehumidistat Instruction Manual

H8908A/B Humidistat;
H8908C/D Dehumidistat
Instruction Manual

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.

CAUTION
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.

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DUCT INSTALLATION

1. Choose a location on the duct.
   

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.
   

3. Run two-fan, low-voltage wire to the mounting location on the duct. See Fig. 5.
   IMPORTANT
   Use rated 18-22 gauge wire. Leave approximately 6 in. of wire to properly connect the humidistat.
   

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.
   

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

3. Run two-fan, low-voltage wire to the mounting location in the living area.
   IMPORTANT
   Use rated 18-22 gauge wire. Leave approximately 6 in. of wire to properly connect the humidistat.
   

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.
   

5. Secure the base bracket to the duct or remote location. Secure to the duct with four 1-in. (25 mm) screws (provided) or to the wall with two 1in. (25 mm) screws (provided).
   WIRING
   CAUTION
   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. 12–18.
   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– 18 for different wiring configurations.
   

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.
   POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
   24 VAC WIRING.
   Fig. 13. Wiring H8908 with 2-speed fan motor.
   POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
   M24729
   24V WIRING.
   Fig. 14. Typical wiring diagram of current sensing relay with humidifier.
   POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
   M24730B
   24V WIRING.
   Fig. 15. Wiring H8908 in line with air pressure switch/sail switch and humidifier.
   24V WIRING.
   NOTE:
   FOLLOW THE INSTALLATION INSTRUCTIONS INCLUDED WITH THE STEAM HUMIDIFIER TO WIRE THE SYSTEM FAN.
   M24731
   Fig. 16. Wiring H8908 with steam humidifiers.
   ONLY NEEDED IF SYSTEM’S THERMOSTAT DOES NOT ISOLATE Y FROM G.
   IF NEEDED, BREAK THE THERMOSTAT G TO SYSTEM G CONNECTION
   AND ROUTE THROUGH HUMIDIFIER AS SHOWN.
   HE150/HE250 USES A 15 VA TRANSFORMER WIRED INTO 24V IN.
   HE100/HE200 USES A 10 VA TRANSFORMER WIRED INTO 24V IN.
   HE300 USES A LINE CORD PLUG.
   Fig. 17. Wiring to force fan on and prove airflow in the duct.
   Fig. 18. Typical wiring diagram for HR150, HR200, ER150 and ER200 Ventilator or DH90 Dehumidifier applications.

CHECKOUT

Turn the H8908 dial to “ON” to test proper installation. See Fig. 19.
You will hear an audible click if installed correctly, and water will begin flowing to the humidifier.

OPERATION

Humidity Control Adjustment
To maintain optimal humidity levels without causing condensation on cold surfaces such as windows, the homeowner must adjust the setpoint as the outdoor temperature changes.
To reduce the relative humidity, lower the setpoint approximately three percent relative humidity every 24 hours. To increase the relative humidity, increase the setpoint approximately three percent relative humidity every 24 hours.
Setpoint Adjustment
Set the humidity setpoint according to the prevailing outdoor temperature. Recommended settings are available on the control and in the table below.
Table 1. Recommended Humidity Controller Settings.

www.resideo.com
Resideo Inc., 1985 Douglas Drive North,
Golden Valley, MN 55422
69-1341EF—09 M.S. Rev. 11-19 | Printed in United States
This product is manufactured by Resideo Technologies, Inc., Golden Valley, MN, 1-800-468-1502
©2019 Resideo Technologies, Inc. The Honeywell Home trademark is used under license from Honeywell International Inc. All rights reserved.

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