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  1. #1
    Join Date
    Oct 2008
    Rochester, NY
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    New Furnace - 2 stage work well with older ducts?

    I have been reading over posts in here about how older ductwork can affect furnace performance and fan noise.

    I live in upstate NY in a 1450 sq. ft. house built in 1928. Currently have a 1980 Williamson oil furnace (100,000 btu), no wall insulation and minimal attic insulation. We are working at getting insulation added and upgrdaing to a gas furnace.

    We qualified for a grant through NYSERDA to get 50% paid upto $5000. That being the case, my heating contractor was keen to sell me their best furnace (3 stage, varable speed 96.6% Carrier). I think that is overkill, but liked the reported savings the variable speed motor offers, plus the increased comfort of the 2 stage. So I am now leaning towards a 92% Payne (2 stage & variable)

    However, given that the ductwork in my house is older (not sure exactly how old) will this negate the 2 stages? Would I be as well saving some money and getting a good single stage?

    Also the new furnace is sized at 60,000 btu, will this be sufficient to heat the house through the old ductwork?

  2. #2
    Join Date
    Aug 2002
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Old corectly sized duct system will work fine,incorrectly sized ,regardless of age is an issue for old and new furnace.

    Equipment size can't be dtermined from here,actuall on site Man. J (from is the best way.

  3. #3
    Join Date
    Jan 2004
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    Your area is a bit colder then mine.

    But even without insulation, a 100,000BTU furnace is over sized.

    Because of that, duct that was undersized for it, may be sized ok for a new 90% unit.

    But, a Manual J should be done, to know what size your home needs, before you end up still having an oversized unit.
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