How to Wire a Damper

Zoned air-conditioning systems use motorized dampers to regulate the amount of air a room receives.

With Spring-Loaded Blades

A motorized damper recieves its signal through low-voltage wires.A motorized damper recieves its signal through low-voltage wires.
When a thermostat in a zone detects a need for conditioned air, it sends a signal to the zone system's control board. The control board then sends a signal to the air handler and the motorized damper that regulates that room's air flow. When the room has reached the desired temperature, the control board tells the damper to close. Motorized dampers with spring-loaded blades use two-strand low-voltage wire. Motorized dampers without spring-loaded blades need three-strand low-voltage wire because they use polarized motors.

Run a two-strand low-voltage wire set from the damper's motor to the inside air-conditioning unit, called the air handler. Cut the wire set to length with wire cutters. A two-strand wire set contains two insulated wires wrapped in a plastic sleeve.

Remove 3/8 inch of the insulation from each wire strand with wire strippers.

Wrap one of the wires from the two-strand wire set around one of the damper motor's wire terminals and tighten the terminal screw with a slotted screwdriver. Wrap the second wire around the second wire terminal and tighten its screw. Spring-loaded dampers do not use polarity-sensitive motors, making the wires interchangeable.

Connect the two-strand wire set to the damper's control unit. Usually a zone system uses an integrated control panel that operates several dampers as needed. If so, then connect one wire from the wire set to the "C" terminal and one to the "Hot" terminal. If the damper hard wires to a thermostat instead of a control panel, then connect one of the wires from the wire set to the transformer's common wire and the second wire to the wire that connects to the thermostat's "W" terminal.

Without Spring-Loaded Blades

Run a three-strand low-voltage wire set from the damper's motor to the air handler. Cut the wire set to length with wire cutters. A three-strand wire set contains three insulated wires wrapped in a plastic sleeve.

Remove 3/8 inch of the insulation from each wire strand with wire strippers.

Wrap the red wire around the damper motor's common terminal, often labeled "Com" or "Common." Wrap the black wire around the damper's close terminal, often labeled "CLS" or "Close." Wrap the blue wire around the damper's open terminal, often labeled "OPN" or "Open." Tighten each terminal screw with a slotted screwdriver.

Wrap the red wire around the control panel's common terminal, usually labeled "Com" or "Common." Wrap the black wire around the control panel's close terminal, often labeled "CLS" or "Close." Wrap the blue wire around the control panel's open terminal, often labeled "OPN" or "Open." Tighten each screw with a slotted screwdriver.

Things You Will Need

  • Two-strand low-voltage wire
  • Wire cutters
  • Wire strippers
  • Slotted screwdriver
  • Wire nuts
  • Three-strand low-voltage wire

About the Author

Based out of Central Florida, Robert Sylvus has been writing how-to and outdoor sports articles for various online publications since 2008. Sylvus has been a home improvement contractor since 1992. He is a certified HVAC universal technician.