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.

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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.

Resources

  • ZoneFirst

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