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  1. #1

    Wink Heating/AC Problem

    Dear HVAC Talk Members:

    I have been living with the problem of having the front 2 rooms of my 2nd floor of my house (the furnace is in the back of the house, in the basement) being hot in the summer and cold in the winter. I live in TOronto, Canada, and temperatures can swing from icy cold in the winter, to hot hazy and humid in the summer.

    We have an 18 year old furnace and AC unit (120,000 BTU and 3.5 tons) made by Keeprite (owned now by Carrier). These units are in very good shape (well maintained yearly). Of course, their energy efficiency is lower than today's newer units...but what we care about is COMFORT IN THESE 2 ROOMS!!!

    THE PROBLEM IN THESE 2 ROOMS is AIR FLOW. WE don't get enough air into the room through the ducts, and so this is causing us issues with getting heat/cold into the room. The ducts are at the "end of the run" and are far far away from the furnace. We want to resolve this, as we are having a baby, and want to make sure that the baby is comfortable.

    A contractor is suggesting, in order to solve our problem, that we do the following:

    1. Change our furnace to a Carrier Infinity 58MVB120 model (2 stage heating unit) - likely a Carrier 96 from what I can read on the internet.
    2. Change our AC unit to a Carrier Weathermaker 2 Speed 38TDB 5 Ton model.
    3. Redo the basement ductwork to create a single special "run" of ducting just for second floor vents.
    3. Install a zoning system, and install controls/dampers to allow the furnace/AC to send air only to the 2nd floor.
    4. Install 2 Infinity thermostats in the house (one on the main floor, one on the second floor).

    IN YOUR OPINION, WILL THIS SOLVE OUR AIR FLOW issues?

    Thanks for your insight/guidance/suggestions.

    Airbus_Guy!

  2. #2
    Join Date
    Sep 2002
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    Throwing high end equipment and zoning at the problem won't necessarily make it go away.

    The problem most likely has more to do with distribution than equipment; consider making the recommended changes to the ductwork without replacing anything.

    Why were you quoted a 5 ton a/c? Does the old unit have trouble keeping up? Did your contractor even determine if the ductwork can handle 2000 CFM? (400 CFM per ton)

    If you want the equipment replaced, get an energy audit done first to qualify for federal government grants and identify areas which need improvement. (Upgrade building envelope if cost effective, install correctly sized equipment)

    http://www.oee.nrcan.gc.ca/residenti...ent.cfm?attr=0
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  3. #3
    Join Date
    Jan 2004
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    Hard to see why you would need to go from 3.5 ton to a 5 ton unit.
    Other wise most of the proposal sounds ok.
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  4. #4
    Join Date
    Apr 2008
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    Alberta Canada
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    I would get 2nd opinion

    Sounds like he is over sizing furnace and air conditioner. If you have a 120 000 BTU furnace and is 60% efficient you out put would be 72 000BTU. you can take a 80 000BTU at 94% and you would have 75 200 out put or in you case 120 000 BTU at 94% and you will 112 800 output. Get another opinion or 2.
    Do it right the first time.

  5. #5
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    Most conventional furnaces are rated at 75-80% of output; in this case it would be a minimum of 90 000BTUs. The 60% rating comes from the standing pilot, open draft hood, and startup/shutdown losses.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  6. #6
    Join Date
    Apr 2008
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    Alberta Canada
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    2,246

    so whats your point

    Quote Originally Posted by amd View Post
    Most conventional furnaces are rated at 75-80% of output; in this case it would be a minimum of 90 000BTUs. The 60% rating comes from the standing pilot, open draft hood, and startup/shutdown losses.
    Just wondering what your point was.
    Do it right the first time.

  7. #7
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    My point is that the new 120k furnace may not be as oversized as it seems, relative to the existing unit.

    I still agree with you though. (quoted equipment likely to be too large)
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

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