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Please Read And Save These Instructions

•  Installation by anyone other than a qualified contractor voids the warranty.

•  Product designed for residential installation only. Commercial installation voids warranty.

•  Modification or alteration of product, parts, installation instructions or local safety codes voids warranty.

•  Read our full warranty policy at the end of this document.

Breathe Healthier

About the MHX3C Digital Humidistat

The MHX3C control provides low voltage control of most humidifiers.  The humidistat uses a SPDT switch and is designed 
for wall mounting in the living area or mounting on the return air duct.

WARNING!  

Always TURN OFF POWER TO THE HVAC SYSTEM prior to installing or servicing the humidifier or 

humidistat.  Improper operation can result in over or under humidification.  Improper voltage can cause malfunction or  

       damage to the control.  All local building and electrical codes must be followed.  The technical specifications for this  
       product and the contents of the user manual are subject to change without notice. 

WARNING!  

Do not set relative humidity too high during cold weather. Over humidification can result in condensation, 

structural damage and mold.  

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Canadian General Filters, Ltd.

400 Midwest Rd. 

Toronto, ON M1P3A9 Canada

Toll Free:  (888) 216-9184

www.cgfproducts.com

General Filters, Inc.

43800 Grand River Avenue

Novi, Michigan 48375

Toll Free: (866) 476-5101

www.generalaire.com

MHX3C  Humidistat

(GFI #7038)

Installation Manual 

 

GENERAL FILTERS

 INCORPORATED

Summary of Contents for MHX3C

Page 1: ...URN OFF POWER TO THE HVAC SYSTEM prior to installing or servicing the humidifier or humidistat Improper operation can result in over or under humidification Improper voltage can cause malfunction or damage to the control All local building and electrical codes must be followed The technical specifications for this product and the contents of the user manual are subject to change without notice WAR...

Page 2: ...Attach directly to the wall using the two screws provided in the slotted holes 5 Connect wires to screw terminals on the control assembly as shown in DIAGRAMS 1 5 Replace the face DUCT MOUNTING ON THE RETURN AIR WALL BASE Humidistat Dehumidistat versions optional Do not install the humidistat on the warm air duct or within 48 of UV light 1 Locate the humidistat at least 24 upstream of the humidifi...

Page 3: ...distat L1 N G Humidifier Control Leads Yellow Wires Humidifier Power Cord Humidifier 24V Aux Power Red Wires 120V Switched With Furnace Heating Cycle DIAGRAM 5 Wiring 120V 1137 1000 Power Humidifiers With Constant 120V Supply Humidifier Control Leads Yellow Wires Humidifier Power Cord Humidifier 24V Aux Power Red Wires L1 N G 727 58 24V Transformer Omit if Power Supply is 20 30 VAC 120V Switched W...

Page 4: ...and C are used on the humidistat These are the contacts for humidification 3 Check voltage at terminals NO and C There should be no voltage for an Elite Steam or 1137 1000 power humidifier Voltage should be 20 30 VAC from most others 4 Verify humidifier operation by bypassing the humidistat Ideal humidity is not achieved 1 Excess air infiltration Seal sources of air loss 2 Technical fault with hum...

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