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  1. #1
    Join Date
    Jun 2014
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    York furnace - variable speed???

    Hi,
    I own a York furnace tm9v080b12mp11ca. It is a 2 stage furnace and based on what I read a variable speed one. That said, the control board jumpers only allow me to select L M H fan speed but not variable like some manual show.

    The result is that my furnace's fan speed is either on or off (currently set at L by the original installer). Because it's in the house, it is rather noisy and variable speed ie. Running at lower speed to maintain temperature would be much better it seems.

    My question is whether I could have an HVAC installer swap out the board for one that would allow variable speed and if I need a specific "communicating" thermostat from York for this to work?

    Thank you!

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    That is a full variable speed motor. It is normal to have little control over your heat speed. The furnace comes set for the CFM York wants for maximum efficiency & comfort. They do allow a tweak like you have. Rheem is the same way. Factory speed or just a bit more or a bit less. Too much air you can condense in the primary heat exchanger, too little air and the furnace overheats. In cooling you should have a lot more control over your blower speed.

    If the blower is noisy, it is either oversized and/or underducted. Hopefully you have a 2 stage thermostat controlling it so it can run on low fire most of the time.

  3. #3
    Join Date
    Jun 2014
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    Thread Starter
    Hi, thank you for the insights and yes it's a 2 stage thermostat. That's said, being a so called variable speed furnace, should it be able to regulate speed up and down as the target temp is reached? I have a cooling unit (different model) that run low CFM as it gets closer to temp and increases as it deviates. This keeps the fan speed optimized. Isn't that possible with a furnace?

    The noise is due to the fact that the furnace is right under a bedroom with poor insulation which I'm going to improve.

    Thanks again!

  4. #4
    Join Date
    Oct 2011
    Location
    Gladstone, Oregon (Portland)
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    This will help. I got this from another site.

    A variable speed furnace blower provides a higher level of performance than a standard blower in that it features a high efficiency Electronically Commutated Motor (ECM) by General Electric.

    This feature is important because full air delivery is only needed a small portion of the time. During lower demand times this motor reduces its speed, providing up to 4 times better humidity control in the cooling mode (when installed as part of an air conditioning system), better air distribution throughout your home, and greatly reduced operating costs.

    Another important feature of a variable speed furnace is the reduction of what is referred to as "cold blow," or the cold blast of air upon heating startup. "Cold blow" results from cold air that develops in the duct system while the heat is in an off-cycle. When the furnace heater fan cycles on, this cold air is moved very quickly into your home resulting in an uncomfortable draft.

    Variable speed furnaces virtually eliminate cold blow with a "soft start," or a gradual increase in fan speed over the initial 3 to 4 minutes of the on-cycle. This cold air is combined with preheated air from the furnace blower and is delivered at a slower velocity until it reaches full operating temperature. The result? Improved heating comfort and a dramatic reduction of the uncomfortable drafts associated with standard furnaces.

    Better air distribution will provide a marked improvement in those areas of your home where air delivery has been a problem, such as the rooms farthest from the furnace.

    In fact, a variable speed blower is so efficient that the low constant fan setting costs about the same to operate as an ordinary 75-watt household light bulb.

    You and your family will appreciate the whisper-quiet operation of a variable speed furnace. The motor is among the quietest ever made and in fact, when combined with the generously applied foil-faced insulation, these are among the quietest furnaces available at any price.

    The lower constant fan speed setting allows for greater removal of impurities by your furnaces' air filter. Click here to learn more about air filtration options.

  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    There are 2 stages of heat and a blower speed for each. Nobody has the blower vary beyond that on a 2 stage furnace. If you were to have a modulating furnace, then there would be anywhere from 13 to 60 stages and the blower follows along.

  6. #6
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Quote Originally Posted by mayoutze View Post
    Hi, thank you for the insights and yes it's a 2 stage thermostat. That's said, being a so called variable speed furnace, should it be able to regulate speed up and down as the target temp is reached? I have a cooling unit (different model) that run low CFM as it gets closer to temp and increases as it deviates. This keeps the fan speed optimized. Isn't that possible with a furnace?

    The noise is due to the fact that the furnace is right under a bedroom with poor insulation which I'm going to improve.

    Thanks again!
    Im betting oversized on undersized ducts!

  7. #7
    Join Date
    Mar 2016
    Location
    Dayton Oh
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    Quote Originally Posted by mayoutze View Post
    Hi, thank you for the insights and yes it's a 2 stage thermostat. That's said, being a so called variable speed furnace, should it be able to regulate speed up and down as the target temp is reached? I have a cooling unit (different model) that run low CFM as it gets closer to temp and increases as it deviates. This keeps the fan speed optimized. Isn't that possible with a furnace?

    The noise is due to the fact that the furnace is right under a bedroom with poor insulation which I'm going to improve.

    Thanks again!
    I believe you are confusing a fully modulating system with a variable speed blower motor.

    A modulating system will ramp up and down as needed based on the inside temp and outside temp. A variable speed blower (what you have) is just a different type of blower motor.

    You have 2 stages of heat: low and high. Therefore during heat, you have 2 fan speeds: low and high


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