Honeywell H8908B1002
Honeywell Humidistat Manual Color White
  Manual Manual Automatic Automatic
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The H8908B Humidistat provides manual low voltage (24 vac) control of humidifiers, in central heating and air conditioning systems. The H8908B has a SPST, snap-acting, dust-proof switch and designed for wall or surface duct mounting.

Color: Premier White

   √ SPST, snap-acting, dust-proof switch
   √ Positive ON and OFF settings
   √ Twelve-inch ribbon of thin nylon ribbon
   √ Mounts in duct or on wall surface

Product Specifications

Description Humidistat
Application Humidification
Type Humidity Control
Voltage 24 Vac
Electrical Rating 50 VA at 24 Vac
Color Premier White
Mounting Duct mount or wall mount
Differential 4% to 6% RH
Temperature Range -20° F to +120° F
-29° C to +49° C
Operating Range 10 to 60% RH
Dimensions (in.) 3¾ in. high x 3¼ in. wide x 2 in. deep
Dimensions (mm) 95.3 mm x 82.6 mm x 50.8 mm deep

Also available in the color Taupe H8908B1010.

H8908 humidtat installation (4 pages 130k pdf)H8908 wiring for trane (8 Pages 173k pdf)
Aprilaire Humidity Info (270k pdf 4 Pages)H8908 American Standards (8 Pages 190k pdf)

Manual Versus Automatic Humidistat

The indoor humidity level needs to be set based on the outside temperature. This is to prevent water from running down the windows. The cool air near the windows can not hold the humidity and water will condense on the glass. To prevent this condensation, the indoor humidity level is sacrificed by lowering the humidistat.

A manual humidistat needs to be set back as the season gets colder. An automatic humidistat (such as the Aprilaire 60) adjusts the humidity by using an outside temperature sensor.

The Honeywell automatic humidistat (H6062A) determines the outside temperature based on the furnace duty cycle or with an optional outdoor sensor. Below the Honeywell owners manual discusses this feature they call HumidiCalc.
Aprilaire Humidity Info (270k pdf 4 Pages)H1008 Installation (519k pdf 16 Pages)

When The Outdoor
Temperature is
This Relative Humidity
Should Be Maintained

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