Results 1 to 8 of 8
  1. #1

    Help, question about Variable Speed Blower

    Hello

    I am a homeowner and I have recently finished a major renovation on my house. My HVAC contractor installed two American Standard Freedom-90 Comfort-R 12 speed variable speed furnaces in the house. There are 4 levels and each furnace runs two zones, one on each level. Each zone has an Aprilaire 8363 thermostat.

    Now I have noticed that the furnaces simply kick on and off like an old fashioned furnace. I do not detect these 12 speeds I have paid extra for. I mentioned this to my contractor and he said he made a few adjustments and now I should detect the different speeds, but I do not think I do. I feel maybe I have the wrong thermostats, ones that do not control the variable speeds. He says it's the furnace that selects the speed, not the thermostat. If the thermostat is set very high above the current temperature, the furnace will "detect" the larger temperature request and blow faster, and if I set it slightly above the current temp it will blow slower. This implies the thermostat somehow "transmits" the set temperature to the furnace. I was not aware that the thermostat could do this.

    I would like to make sure that I am getting what I paid for, a multi speed HVAC system. I'm not sure I am. I think it's the thermostats that are wrong. Does anyone know if the 8363 is the right thermostat? Is my HVAC guy correct in telling me how the speeds would be selected? Also how would it provide two different speed requests to the two zones given that each furnace only has one blower?

    Please help an uneducated consumer. Thanks.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,347
    Where does 12 speed come from?

    That furnace is a 2 stage meaning it has a high and a low fire. Depending upon the zone panel, the fire rate may be selected by the panel, the thermostats or time up after so many minutes of running on low. You'd have to know how the installer designed it to know how yours will perform. If sounds like he is using the thermostats to pick high or low fire. That can be good or bad as often 1 zone cannot handle all the heat if the furnace burns on high.

  3. #3
    Join Date
    Aug 2006
    Location
    Wisconsin
    Posts
    1,506
    Start with a model number of your furnace.
    Buy American! The job you save may be your own.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,370
    Start with the furnace mod number.
    And then the zone panel.
    And then the size of the floors/zones.
    If the furnace is over sized too much, you won't ever notice it going to second stage.
    Contractor locator map

    How-to-apply-for-Professional

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

  5. #5
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    It isn't a "12 speed" blower.
    The variable speed blower and controls have 12 maximum cooling airflow settings available via the dip switches.
    Then depending on control inputs, there are 16 steps, from 25% through 100% of the max cooling airflow setting. Very few systems will use more than a handful of the 16 possible steps. I think Trane's zoning system is the only thing that would possibly use them all.

    The heating airflow is a separate setting, and on gas furnaces will only run at 2 airflow levels. One for low fire, and one for high fire.

    The thermostats in your system just tell the zone control that the zone needs heat, the zone control cycles the equipment. The zone control opens dampers to the zones that are calling for heat, and runs the furnace in low or high fire. There are several ways a zone control could determine whether to run low or high fire, depending on settings and control inputs.
    There isn't a way that it could provide 2nd stage to one zone, but only 1st stage to another.

    It sounds to me like you have some unrealistic expectations.
    Last edited by mark beiser; 03-31-2008 at 09:28 AM.
    If more government is the answer, then it's a really stupid question.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,370
    Or the salesman made some outlandish claims.
    Contractor locator map

    How-to-apply-for-Professional

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

  7. #7
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    Quote Originally Posted by beenthere View Post
    Or the salesman made some outlandish claims.


    Never.
    Perhaps you should have read the instructions before calling.

  8. #8
    Join Date
    Apr 2004
    Posts
    7,680
    JR, I like your sig line... haha

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event