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Make My Rheem (Weather King) 90RJ Operate on Two Speeds

SteveJF
SteveJF Member Posts: 3
in Gas Heating
I'd like to have my furnace blower motor run constantly on low to improve air flow and filtration. I'd like the blower to change to Medium (Heating) or High (Cooling) when the thermostat calls for either heating or cooling. Does anyone know how to do that on a 90RJ? Thanks.

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,744
    I believe that this happens when you set the thermostat to Fan On.

    When there is a call for heat, the vari speed blower will ramp up bases on stage one or stage two. Same on Cooling. When the thermostat is satisfied the fan will operate at about 10 or 15% speed so you dont get a draft.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • realliveplumber
    realliveplumber Member Posts: 354
    Iirc, the 90rj is a basic, single stage 90% furnace.
  • SteveJF
    SteveJF Member Posts: 3
    edited November 2023
    Thanks. It is not a vari-speed blower motor. Yes - It's has a single stage heating section. The blower motor has Lo-med-hi taps. Setting the thermostat to "Fan On" brings the blower speed to Hi. I'd like it to set the blower on Lo.
  • pecmsg
    pecmsg Member Posts: 5,545
    What speed does it run when calling for heat?
    SteveJF
  • HVACNUT
    HVACNUT Member Posts: 6,468
    You can use whatever speed you want for "Fan On" but if you change the fan speed on the heat side it needs to be within specs on temperature rise.
    SteveJF
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,893
    You would need a relay or maybe a couple of relays. I attached a drawing of something I just dreamed up.

    Not really a complete wiring diagram just a concept of what might work. Not saying it will work just something to mull over
    SteveJF
  • SteveJF
    SteveJF Member Posts: 3
    Thanks! I thought adding a relay may be the only way to accomplish the two speed operation and the schematic is very helpful!
  • John Mills_5
    John Mills_5 Member Posts: 952
    I believe fan on is heat speed and when Y is called for to bring the cooling on, it also changes the blower to cool speed. That isn't always high, it should be set to the appropriate speed for the size of the A/C.

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