Honeywell H8908A-B Low Voltage Humidistats Installation Guide
- June 17, 2024
- Honeywell
Table of Contents
H8908A/B Humidistat
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…
- Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.
- Check the ratings given in the instructions and on the product to make sure the product is suitable for your application.
- 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.
DUCT INSTALLATION
- Choose a location on the duct.
- 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.
- 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
-
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 athrooms or itchens. See Fig. 6. -
Cut 1 in. diameter wire hole in wall.
-
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.
-
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.
-
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 1-in. (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. 12–19.
IMPORTANT
Select models of fan centers include humidifiertaps 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. -
Using wire nuts, connect the low-voltage wire to the leads on the H8908 humidistat. See Fig. 6–19 for different wiring configurations.
-
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.
CHECKOUT
Turn the H8908 dial to “ON” to test proper installation. See Fig. 20.
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 5temperature changes.
To reduce the relative humidity, lower the setpoint approximately three
percent relative humidity every 245 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 Settin gs.
Outdoor Temperature| Recommended
H8908A,B Setpoints
---|---
°F| °C
-20| -29| 15
-10| -23| 20
0| -18| 25
10| -12| 30
20| -7| 35
+20| >-7| 40
Outdoor Temperature| Recommended H8908C,D Setpoints
---|---
°F| °C
70| 21| 50
75| 24| 40
80| 27| 35
85| 29| 30
90| 32| 25
+100| >+38| 20
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Honeywell International Inc.
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