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  1. #1
    Join Date
    Oct 2008
    Location
    Rochester, NY
    Posts
    3

    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
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    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 www.acca.org) is the best way.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,763
    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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