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  1. #1
    Join Date
    Oct 2004
    Posts
    22
    At what point does a Dual Stage gas furnace use the low stage. And at what point does it revert to the high stage.
    The T-stat is a Honeywell programable set to Dual stage heat single stage cool. If I raise the stat temp 1 degree it sounds
    like the furnace fires on low for a few seconds then goes to high fire and high draft. But I am not sure

  2. #2
    Join Date
    Apr 2004
    Posts
    7,680
    If you are using a two stage thermostat, it will for the most part start in low fire unless of course you change the set point requiring more heat. If the stat just naturally calls for heat, it will fire in 1st stage. If 1st stage begins losing ground, it will switch to 2nd stage. If you prefer a timed sequence, a single stage stat set up would be the selection. (a two stage can work as one stage).

    Now, it's always possible the unit needs to be configured to know a two stage stat is being used or it may also be wired incorrectly. All furnaces are different so the only consideration is to read the instructions that came with the furnace, not the stat.

  3. #3
    Join Date
    Oct 2004
    Posts
    22
    The furnace is a Goodman GMV90703BXA Dual stage the stat is a Honeywell Focus Pro TH6220D I am not hearing any difference in the Induced draft blower speed when the furnace is running after a night time setback of 10 degrees. Installer is coming back on Fri to check things out.

  4. #4
    Join Date
    Oct 2005
    Posts
    88
    There's a jumper on the GMV9 board labeled TSTAT that should be in the TWO position, not the SINGLE position. If that's right, and the stat is really closing R-W1 for low heat and R-W2 for high, you should be in business.

    The difference in draft inducer sound between low and high might be hard to hear if you're not right there to hear when it changes. You've probably noticed a cycle always starts with a prepurge on high draft, always steps to low draft before ignition - then if the call is for high fire, it steps back up after flame is established.

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    Originally posted by carlosr
    The furnace is a Goodman GMV90703BXA Dual stage the stat is a Honeywell Focus Pro TH6220D I am not hearing any difference in the Induced draft blower speed when the furnace is running after a night time setback of 10 degrees. Installer is coming back on Fri to check things out.
    The furnace doesnt care what the set point is, 55 or 85, its controlled by the thermostat. Its really just a matter of how FAR from set point the room is.

  6. #6
    Join Date
    Oct 2004
    Posts
    22
    [QUOTE]Originally posted by chapmanf
    [B]There's a jumper on the GMV9 board labeled TSTAT that should be in the TWO position, not the SINGLE position.

    The jumper is in the 2 stage position. I am not working on it
    But I just had to look before he got there.
    Installer is a nice guy But he did say this was his first Dual Stage he had put in. He mostly puts in 80% and a few 90+ units
    mostley Goodman. Thanks

  7. #7
    Join Date
    Oct 2004
    Posts
    22
    Originally posted by docholiday
    Originally posted by carlosr
    The furnace is a Goodman GMV90703BXA Dual stage the stat is a Honeywell Focus Pro TH6220D I am not hearing any difference in the Induced draft blower speed when the furnace is running after a night time setback of 10 degrees. Installer is coming back on Fri to check things out.
    The furnace doesnt care what the set point is, 55 or 85, its controlled by the thermostat. Its really just a matter of how FAR from set point the room is.
    So the furnace needs be wired the way it says in the Goodman
    install manual for Dual stage heat single stage cool and not by the T-Stat manual

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