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Johnson Controls W42AA Type Low or Line Voltage Humidistat

Low or Line Voltage Humidistat
W42AA Type

The W42AA humidistat provides single pole, double-throw control for use on low or line voltage applications.

The humidistat’s terminals are marked for easy wiring. The “C” terminal is common. The circuit between “C” and “L” terminals closes on a decrease in relative humidity.

The circuit between “C” and “H” terminals closes on an increase in relative humidity. The humidistat’s sensing element consists of approximately 150 strands of carefully selected and processed human hair -- proven to be the most sensitive and stable material known for humidity control. An exclusive tension release device keeps the hair strands from being damaged by extreme humidity or mechanical strain. The sensing element is mounted vertically to minimize surface contamination by dust or foreign material.

The humidistat mounts on a standard outlet box or directly to a flat surface where permitted by electrical codes.

• Three-wire SPDT switch permits control of humidifying or dehumidifying equipment or both with one control
• Stable and accurate human hair sensing element
• Easy to read dial is adjustable over a range of 10 to 90% RH
• Concealed dial lock screw for sealed setting
• Separable mounting plate with mounting screws attached, saving installation time.
• Attractive contemporary styling

Select a link under the "item" tab below to order.

Cat #Descriptions
W42AA TypeLow or Voltage Humidistat
Type: W42A Low or Line voltage Humidistat
Range: 10-90% RH
Differential 4% RH
Maximum Operating Ambient Temperature: 100°F (38°C)
Contact Action: SPDT
Electrical Rating Pilot Duty Only: 120 VA at 120/240 VAC
Material: Base Molded Thermosetting Plastic
Cover Metal Cover with Ivory Enamel Finish
Packaging: Individual Pack in Reshippable Corrugated Carton
Shipping Weight Individual Pack 0.6 lb (0.3 kg)
Overpack of 20 14 lb (6.4 kg)


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