Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Honeywell L4064B fan limit switch help

NiSiSuinegEht
NiSiSuinegEht Member Posts: 1
edited June 2021 in Thermostats and Controls
I have a Honeywell L4064B fan limit switch on my oil furnace that is missing the Manual/Auto knob.



Is the missing knob actually the override switch, or does it just actuate a switch inside the limit switch housing?

Can I install an external switch to manually bypass from the Line to Load terminals on the Fan side? I want to be able to run the fan to circulate cool air from the basement through the house ducts.

My thermostat only has red/white wires, so there is no fan control wired in.

Comments

  • mattmia2
    mattmia2 Member Posts: 9,572
    You could add a manual switch or a relay controlled by the thermostat's g terminal.
  • Ctoilman
    Ctoilman Member Posts: 105
    simplest approach would be to add a switch that would give power to the furnace blower motor.  BUT what type of blower motor do u have?  If its old school belt Drive, then it's easy-peasy to add a switch, not so simple if it's a multi-speed PSC direct Drive motor.  Or, if its an ECM motor then thats a whole nother scenario.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    You don't want the fan running all the time, especially for AC.
    steve
  • rick in Alaska
    rick in Alaska Member Posts: 1,457
    I would just change out the control to one that has that feature.
    Rick
    SuperTech
  • pecmsg
    pecmsg Member Posts: 4,775

    I have a Honeywell L4064B fan limit switch on my oil furnace that is missing the Manual/Auto knob.



    Is the missing knob actually the override switch, or does it just actuate a switch inside the limit switch housing?

    Can I install an external switch to manually bypass from the Line to Load terminals on the Fan side? I want to be able to run the fan to circulate cool air from the basement through the house ducts.

    My thermostat only has red/white wires, so there is no fan control wired in.

    Is your return in the basement?
    SuperTech