In this video, Ask This Old House plumbing and heating expert Richard Trethewey shows how to divide a home’s heating and air-conditioning system into different zones.
Steps for Zoning a Forced-Air Furnace & AC Unit
- Cut into each flexible branch duct and install a motorized zone damper. Secure the damper to the duct with nylon cable ties.
- Make the wire connections at each motorized damper and run all the wires back to the control panel at the furnace.
- Remove the control panel’s cover and plug in the telephone jack connections for each zone.
- To maintain the proper pressure within the system, install a weighted bypass damper between the supply trunk and return trunk.
- Seal all the duct joints with mastic or foil-faced duct tape.
- Adjust the weights on the bypass damper to ensure proper airflow to all registers.
- Find a suitable spot in the house to install a wireless thermostat to control the new zones. To ensure accurate readings, place the thermostat away from direct sunlight and heating registers.