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  1. #1
    I'm replacing my 30 plus year old furnace with a new 2-stage and variable speed furnace. For thermostat, the contractor will be using an Aprilaire model 8363 which is for a 1-stage furnace. The contractor explained to me that they do this all time......instead of putting in another wire (old thermostat has only 5 wires) to accomodate a thermostat designed for a 2 stage furnace (needs 6 wires), the new furnace's circuit board (?) is adjusted/programmed so the thermostat for a 1-stage furnace can be use.

    Can you pair a 2-stage variable speed furnace with a thermostat designed for a 1-stage furnace without compromising the 2-stage and variable speed features of the new furnace?

    Thank you.

  2. #2
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Don't spend the $$$ on a nice variable speed system and then disable it with a poor control(t-stat). Get the best t-stat you can....it's a comfort and $$$ saver.He should run new stat wire.
    If everything was always done "by the book"....the book would never change.

  3. #3
    Join Date
    Mar 2001
    Posts
    715
    Homeowner
    I would insist on a two stage thermostat for your system. If pulling a new wire isn't possible there is a little circuit board called add-a-wire that will solve that problem and allow you to use your existing thermostat wire.

  4. #4
    Join Date
    Apr 2006
    Location
    Appleton
    Posts
    34
    My understanding as a homeowner is with a 1 stage stat the system is set up on a timer for the second stage to come on versus coming on by need and demand with a 2 stage stat. Thanks

  5. #5
    Join Date
    Mar 2004
    Location
    Illinois
    Posts
    6,959
    Will it work...yes
    Should it be a 2-stage stat...yes.

  6. #6
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,340
    As a contractor I like a timed 2 stage. If the system is design perfect, then on the coldest design temperature day of the year the furnace with not keep up. You need the full capacity of the furnace on the coldest day of the year, with a 2 stage stat you dont get that.

    I remember back in the 80s when the first 2 stage Lennox a/c units came out. The biggest complaint was when it was 90+ degrees out the indoor temp would stay 2-3 degrees below the set point. So in the 90s when the 3rd generation 2 stage units came out, they had a latch option which allowed us to set a timed 2nd stage. If the unit ran 1st stage for 15 to 30 minutes, then it would kick up to 2nd stage and satisfy the demand.

    We still time 2nd stage heat on the furnaces we install. Unless we do zoning on it, then we use a duct sensor to control the 2nd stage.

  7. #7
    Join Date
    Mar 2001
    Posts
    715
    I am a contractor and also own a two stage furnace. I do NOT like the timed feature as well as using a two stage thermostat. I have used the same Lennox furnace both ways. When you use the timed feature the furnace will fire on low then after the time has expired it will go to high fire satisfy the demand and turn off, then the process will repeat. When a two stage thermostat is in control of the furnace the unit may not go to high fire at all during mild conditions, but will when the furnace can't keep up with demand with low fire during colder weather.This results in much longer cycles and the temperaures will be very constant. As tempratures fall toward design conditions the furnace will alternate between low and high fire to keep up with the demand.
    The decision to purchase a two stage furnace should be made for comfort not energy savings. Two stage operation is not more energy efficient than a comparable single stage unit. Our home has never been more comfortable, but only after installing a good two stage thermostat to control the furnace.

  8. #8
    Join Date
    Jul 2006
    Location
    Duncan
    Posts
    134
    they also make a wire less thermostat you might want to check out.

  9. #9
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,340
    What 2 stage thermostat will put the furnace into 2nd when it cant satisfy the load? All the the 2 stage thermostats I know of are controled by a deadband of 2-10 degrees, depending on installers setup.


    [Edited by ascj on 07-27-2006 at 10:10 PM]

  10. #10
    Join Date
    Jul 2006
    Location
    Lancaster,Ohio
    Posts
    464
    The old two stage stats were mechanical stats with two mercury bulbs in them and required a couple of degrees temp change to activeate them. the aprilaire stat is a electronic stat and is highly sensitive. It will know which way the temp is going before the room temp flexuated one degree. Two stage stats cost more than a timer to wire in from first to second stage. You will loose the stats logic center. If it were mine, I would insist on a two stage aprilaire Stat!
    IcyFlame

  11. #11
    Join Date
    Jul 2006
    Location
    ooooo
    Posts
    18

    Hmm DO IT RIGHT ARE NOT AT ALL

    HAY THERE
    THERE IS DIPS ON THE UNIT BUT HES TAKING OUT THE 2ND STAGE FROM YOU.YOU PAYED HEM TO DO IT RIGHT SO TILL HEM THAT YOU WHANT THE TWO STAGE STAT AND THAT IT AND HE CAN RUN A NEW LOW VOLTAGE WIRE ,IF HE CANT FISH IT THOUTH WERE THE OLD WIRE IS YOU CAN RELOCATE IT SO THAT YOU CAN ,BECOUSE IF YOU DONT HAVE A TOW STAGE STAT THE UNIT WILL NOT WORK RIGHT AT ALL THE GUY IS TRYING TO SAVE SOME CASH ARE JUST TO LAZY TO RUN A NEW WIRE..

  12. #12
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,764
    2 stage furnace is for comfort. Using the furnace boards timer eliminates some of that comfort. Meaning your paying for some thing your not getting.

    Its your money if you wish to waste it with a single stage stat.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  13. #13
    Thanks all. Got the 2 stage thermostat (Aprilaire 8570).

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