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  1. #1
    Join Date
    Jul 2012
    Location
    SW Pennsylvania
    Posts
    6

    Question American Standard Variable Speed Blower

    Hi everyone,
    I'm new to this site, so please bear with me.

    Here's the deal:

    I have an American Standard hi-efficiency 2 stage furnace (model number AUH2B080A9V2VAA). It's about 4 years old. I have a Honeywell RTH7400D programmable t-stat. Everything appears to work OK, but there's no way to turn the fan on manually other than turning it 'ON' at the t-stat. It's either ON or AUTO. I'd like to bypass the t-stat in order to be able to turn the fan on so it will run at a higher speed than it does when it's in the ON position at the t-stat. It runs constantly at a very low speed when it's set to ON at the t-stat. This would be nice in the summer when it's not extremely hot outside and I'd like to have more airflow throughout the house. On older furnaces, you used to be able to flip a switch on the furnace to turn the blower 'ON'.

    Has anyone ever done this, or can this even be done?

    One other thing is that I'm not 100% sure that the t-stat is hooked up properly as it only has R, W, Y and G connected, although there is a terminal for W2 on both the t-stat and furnace. I'm under the understanding that for the 2 stage furnace to work properly, both W and W2 have to be connected. Does that sound correct?

    Thanks in advance for any advice/help you can give me. It is truly appreciated.

    Guido

  2. #2
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Sounds like the installer took a shortcut or didn't want to run new thermostat cable. Its' not wired for 2 stage. It probably upstaages after a default timer (I think 7.5 minutes) on the furnace control board.

    I'm not sure there's a good way to do what you want. There may be dip switches to set the furnace to run 75% of 100% instead of 50%, but you won't be able to toggle between the speeds.

    Keep in mind that depending on you ductwork (how restrictive it is), running the fan ccan consume as little as 200Watts or as much as 500 Watts or more when running. That could cost you $1/day. Just something to keep in mind.

  3. #3
    Join Date
    Jul 2012
    Location
    SW Pennsylvania
    Posts
    6
    Hi motoguy128,
    Phew...thanks for the quick reply !
    As far as the installer taking a shortcut, here's the best part: I had already run a new t-stat cable a week before the scheduled installation of the furnace and AC. It appears he didn't wire it properly, eh?
    Yeah...the burner comes on for a while, then the blower ramps up, but I'm thinking like you said, that the furnace isn't upstaging according to the t-stat setting.
    I have the install manual for the furnace...I think I'll hook up the remaining wire W2 and see what happens. 'Course I'll have to wait 'til fall to see what effect it has. Too hot for heat at this point...I'm in SW PA near Pittsburgh.
    Thanks again for your reply.
    Guido

  4. #4
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I don't know if that thermostat has to be configured as well. You might look-up the manual for that as well.

    Given the shortcuts you've already seen. You might want a different company to come out and check the system over before heating season. There might be other things they took shortcuts on... like PVC glue of vent pipes, setting the gas pressure and so on.

  5. #5
    Join Date
    Jul 2012
    Location
    SW Pennsylvania
    Posts
    6
    Have a manual for the t-stat...I configured it myself after the installation, so I'm relatively sure it's set properly, but I'll double-check it.
    Good idea to have another company check it out, although from what I can see physically, (PVC glue, etc.) all appears to be OK. As for gas pressure and stuff like that, I wouldn't even attempt that myself.
    Thanks for the suggestions.

  6. #6
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by guido49 View Post
    Hi everyone,
    I'm new to this site, so please bear with me.

    Here's the deal:

    I have an American Standard hi-efficiency 2 stage furnace (model number AUH2B080A9V2VAA). It's about 4 years old. I have a Honeywell RTH7400D programmable t-stat. Everything appears to work OK, but there's no way to turn the fan on manually other than turning it 'ON' at the t-stat. It's either ON or AUTO. I'd like to bypass the t-stat in order to be able to turn the fan on so it will run at a higher speed than it does when it's in the ON position at the t-stat. It runs constantly at a very low speed when it's set to ON at the t-stat. This would be nice in the summer when it's not extremely hot outside and I'd like to have more airflow throughout the house. On older furnaces, you used to be able to flip a switch on the furnace to turn the blower 'ON'.

    Has anyone ever done this, or can this even be done?

    One other thing is that I'm not 100% sure that the t-stat is hooked up properly as it only has R, W, Y and G connected, although there is a terminal for W2 on both the t-stat and furnace. I'm under the understanding that for the 2 stage furnace to work properly, both W and W2 have to be connected. Does that sound correct?

    Thanks in advance for any advice/help you can give me. It is truly appreciated.

    Guido
    It can be wired to run 100% instead of 50% for constant fan.

  7. #7
    Join Date
    Jul 2012
    Location
    SW Pennsylvania
    Posts
    6
    Hi Second Opinion,
    I kinda figured that...just have to read the manual thoroughly and hope it tells me what I need to know.
    Thanks for the input.

  8. #8
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by guido49 View Post
    Hi Second Opinion,
    I kinda figured that...just have to read the manual thoroughly and hope it tells me what I need to know.
    Thanks for the input.
    Unfortunately you will only find it in the ECM motor manual. If you send me an E mail I can forward you the page or ask your dealer to see page 22 of pub #34-3402 under Fan Continuous Operation for the wiring directions, it is a simple procedure.

  9. #9
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    Could be wired for only 1 stage also relies on static pressure

  10. #10
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,905
    Running the blower constant can raise the humidity level in the home

  11. #11
    Join Date
    Jul 2012
    Location
    SW Pennsylvania
    Posts
    6
    I'm thinking only about running the blower 'on demand', like nice sunny days when it's not that hot outside (around 75 or so) and I have all the windows open anyway.

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