Variable speed + type of t-stats?
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  1. #1
    Join Date
    Jul 2006
    Posts
    20
    I'm finally getting the install and have appreciated the help and professionalism on this board.

    Question about t-stats.

    - I am having an old oil forced air furnace replaced with an American Standard Comfort-R 2 stage, variable speed gas furnace (local gas company heavily subsidizes the equiptment on conversions). Do I need a 2-stage thermostat to take advantage of the 2 stage variable speed features?

    - I am also have a new central a/c installation: the a/c is from the attic while the furnace is from the basement. The a/c is Trane 14xli. The contractor said that the supplier didn't have the air handler in stock that he was going to use, so instead we're upgrading to a variable speed Trane (4TEE3F40A). Seems like a good deal at an extra $400 after qualifying for the energy rebate. Same question here. Since this is a separate unit it will have it's own t-stat. Do I need a special t-stat to take advantage of the variable speed features?
    Also, is this a worthwhile upgrade?

    -Right now they are planning on using 2 Robertshaw 9600 digitat programmable thermostats.

    Today they put in the new furnace, hung the air handler and readied the compressor. They said it should take the whole week (all new duct work in attic, new gas line in basement...)

    THANKS!!

  2. #2
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    Originally posted by booker

    Question about t-stats.

    - I am having an old oil forced air furnace replaced with an American Standard Comfort-R 2 stage, variable speed gas furnace (local gas company heavily subsidizes the equiptment on conversions). Do I need a 2-stage thermostat to take advantage of the 2 stage variable speed features?


    Yes, You should get a two stage t-stat on this nice furnace. No point of "Crippling" this. The two stage t-stat will give you a much better COMFORT results. I've changed out a couple of family memebers t-stat to a two stage, and they noticed incressed in comfort in the home.

    I am also have a new central a/c installation: the a/c is from the attic while the furnace is from the basement. Since this is a separate unit it will have it's own t-stat. Do I need a special t-stat to take advantage of the variable speed features?
    Where are each t-stat at? Upstairs and main floor? If they are both in the same area, you can use one t-stat for this. Only draw back on one t-stat if you want to run the fan "ON", only the fan in the air handler will run. Unless you ask them to put a switch on the furnace itself that you can turn on that fan.

    -Right now they are planning on using 2 Robertshaw 9600 digitat programmable thermostats.
    That is a single stage t-stat. Upgrade to a two stage t-stat. (For heating) Single is fine for the A/C only if you are not going to use one t-stat.

  3. #3
    Join Date
    Jul 2006
    Posts
    20
    THanks.

    Placement of t-stats:
    - Heating thermostat is currently in the main hallway downstairs, and I'm assuming will stay there.
    - T-stat for cooling is planned for the 2nd floor, though specific locaation hasn't been determined (we're more concerned about cooling for upstairs).

    - Upstairs unit will have an Aprilaire filter and we're told that in the winter, we can run it on fan to clean the air. Makes sense?

  4. #4
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    ok, you can do two t-stat.

    -downstairs use two stage t-stat.

    -up stairs use the white roger that they are planning on putting in.

    are the ducts in the attic new or old?

  5. #5
    Join Date
    Jul 2006
    Posts
    20
    mayguy,
    The ducts in attic will all be new. We have not had central air, so it is a completly new install. Does the question of old vs new ducts have a bearing on the type of t-stat?

  6. #6
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    No, just want to make sure it gets insulated. otherwise, they are going to be cool in the winter when you run the fan.

    Why two unit? Why not just use the furnace itself for A/C or is the house too big?

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