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Thread: A Coil

  1. #1
    Join Date
    Jan 2005
    Posts
    109
    Ever hear of putting in a 3.5 ton coil with a 3 ton condensing unit? Should it be done?

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,156
    Very commonly done to get a bit more SEER but also reduces the humidity removal a bit. Do it only if that's the manufacturer's ARI match.

  3. #3
    Join Date
    Feb 2004
    Location
    southern illinois
    Posts
    5,522
    more efficent...less humidity removal,been talked about alot on here....might try the search.

  4. #4
    Join Date
    Jan 2005
    Posts
    109
    Bidding on the job now. Did a calc. on the house and it comes up to 3 tons. That's what the HO has now and he said it didn't do the job. Looked at his furnace,75,000 btu input. Problem...supply only 14X8. Same size trunk all the way to end. His upstairs is cold in the winter. Wants to replace furnace also. Did a heat loss on the house,said unit should be a 60,000. HO added a big addition to the house and it has its own heating and cooling system. Problem is that addition has big entry ways on both floors. Opens up old part of house. He is kind of tight with the money. I am going to suggest fixing main supply duct to proper size,replacing furnace with 80,000btu 90%. I'm thinking keeping the 3 ton cond. unit and throwing in a 3.5 ton coil. If it still doesn't cool I could replace cond. unit later.

  5. #5
    Join Date
    Jan 2005
    Posts
    109
    I forgot,HO is finishing basement. That was in my calc.'s.

  6. #6
    Join Date
    Aug 2004
    Location
    west hartford, ct
    Posts
    74
    Sounds to me like your on the right track for sizing purposes. I like the idea of 3.5 ton coil with existing 3 ton condenor. The 14x8 supply is way to small and sounds like his #1 problem. 26x8 supply would be better. Is the return also undersized?

  7. #7
    Join Date
    Jan 2005
    Posts
    109
    Return is 14X8 also,the whole length.

  8. #8
    Join Date
    Aug 2004
    Location
    west hartford, ct
    Posts
    74
    The return is also undersized and should be fixed. A 3 ton unit would need about a 16" round return. That 14x8 must be noisey.

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