How to Wire a 110V Inline Duct Fan With a 24V Thermostat


Inline duct fans have two primary wiring configurations. The first configuration requires the use of the standalone thermostat control box. The control box is mounted on the ventilation duct and turns the inline duct fan on or off as needed based on the air temperature in the ventilation duct. The second wiring method uses a 24-volt to 120-volt relay to connect the inline duct fan to the main thermostat that controls the heating and cooling system. In this configuration, the inline duct fan will come on when the main fan comes on.

Things You'll Need

  • Wire cutters
  • Wire strippers
  • Inline duct fan
  • 24 to 120-volt relay switch
  • Black electrical wire
  • White electrical wire
  • Cut the electrical plug of of the end of the wire running to the inline duct fan. Strip 1/2 inch of insulation off of the ends of the white, black and green wires.

  • Connect the black and white wire of the inline fan to the 120-volt fan side of the control relay. Then connect the 120-volt supply side of the relay to the junction box that will provide power to the fan. Make sure the power to the junction box is off at the main power panel before splicing any wires.

  • Connect the black and white wires of the junction box to the two supply terminals of the relay. The black wire should be connected to one terminal and the white wire to the other terminal.

  • Locate the two 24-volt terminals on the control relay. Connect these two wires to the 24-volt fan control terminals on the main thermostat. Turn the power back on and turn on the system fan. The inline fan should come on also.

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  • Photo Credit Jupiterimages/ Images
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