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  1. #1
    Join Date
    Jan 2009
    Location
    Springfield,Illinois
    Posts
    7

    New system air and heating

    Hello everyone.........I need some info on an airconditioner,or heat pump and gas furnace, old air is 3.5 tons dont know furnace output, have a couple proposals already one left me a manual j 8th edition report which says for heating summary equipment load 63012 btuh and latent cooling equipment load sizing total load 33695 req. total capacity at 0.70 SHR 3.3 tons.

    My old system installed in 1989, house is 2100 sq ft, 2 story got proposals on airconditions and heat pump in the 13 seer,14 seer and 15 seer with a 3.5 tons also furnace 92.1 afue mcb 93000btu, 93.1% afue mtb 94,000 btu and 95% ics 93000btu all are for Carrier system so far

    My question is that I want good systems without over doing them , not larger than needed,wont be making a decision until late march.

    I live in southern Illinois

    Thanks

  2. #2
    Join Date
    Dec 2003
    Location
    south NJ shore area
    Posts
    360
    we use RHVAC for manual "J" load caluation and it does a good job but some area need more heat or a/c btus do to infiltration in your area. Get a list of referances go check them out call , stop by, are they listed w/ the BBB. have the had any problems weigh the pro`s and con and you will be off when spending your with a company that you`vd checked out and has your confindence.
    GOOD WORK IS NOT CHEAP! AND CHEAP WORK IS NOT GOOD!

    IF YOU THINK A GOOD HVAC COMPANY IS EXPENSIVE. THEN YOU SHOULD TRY A BAD ONE.

  3. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    I wouldn't put more then a 80,000 BTU input 90% in.
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  4. #4
    Join Date
    Sep 2006
    Location
    Leavenworth KS
    Posts
    310

    Smile

    I think you would be with a smaller a/c and furnace. Some thing like 3 ton A/C with no larger than 80k btu. A multistage system will provide better co
    Mike

  5. #5
    Join Date
    Nov 2008
    Location
    Chapel Hill, NC
    Posts
    1,070
    You could go with the larger units if they are multistage.

  6. #6
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Nothing wrong with using a 3.5 ton when the calc says 3.3 ton load.

    Using a larger 2 stage furnace, just means he loses some of the comfort he pays for. Since he won't get the long run times at milder out door temps.
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  7. #7
    Join Date
    Sep 2004
    Location
    Jersey
    Posts
    389
    I would also go with the 80k furnace with 2 stage and vari speed blower, and i would go with the 3.5 ton with 2 stage compressor.
    You will get the longer run times and comfort levels you are looking for.
    Ride hard on a Harley!!

  8. #8
    Join Date
    Nov 2008
    Location
    Chapel Hill, NC
    Posts
    1,070
    By "larger", I meant 90,000BTU/3.5ton.

  9. #9
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Quote Originally Posted by merlin73 View Post
    I would also go with the 80k furnace with 2 stage and vari speed blower, and i would go with the 3.5 ton with 2 stage compressor.
    You will get the longer run times and comfort levels you are looking for.
    Trane makes a 2.5 ton 2 stage.
    Don't know of anybody else that makes a 2 stage of any other size in half ton sizes.
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  10. #10
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,776
    Quote Originally Posted by sktn77a View Post
    By "larger", I meant 90,000BTU/3.5ton.
    First stage is usually 65% of high fire/
    so 65% of 90,000 is 58,500, not much less then his design load BTUs.

    An 80,000 would getr him below 50,000, so he could have longer run times, and still have capacity to spare.

    See the post by key1cc, about his over sized 2 stage furnace.
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  11. #11
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,763
    That seems really big for 2000 sf! What infiltration did they figure?

    Are you air sealing and insulating so you can get smaller equipment? Did they do a blower door test (I do for all new heating equipment recommendations - then I show the benefit of an extra day's labor tightening the house up)?

    I'd think 60-80mbtu multi-stage and 2-2.5 ton should be plenty at 6000 degree days. If you are a "user" of air conditioning (v/s 5 days a summer) stretch for multi-stage.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  12. #12
    Join Date
    Jan 2009
    Location
    Springfield,Illinois
    Posts
    7

    new system air and heating

    Thanks for everyones info new system, I will be getting a blower door test from my utility company just have to call them and set it up so I can insulate and chaulk house; to cut down on some air pockets house is 20 years old , that way I can buy the correct aircondition and furnance. Dont want to overkill or underkill the systems.

    thanks

  13. #13
    Join Date
    Nov 2008
    Location
    Chapel Hill, NC
    Posts
    1,070
    Quote Originally Posted by beenthere View Post
    First stage is usually 65% of high fire/
    so 65% of 90,000 is 58,500, not much less then his design load BTUs.

    An 80,000 would getr him below 50,000, so he could have longer run times, and still have capacity to spare.

    See the post by key1cc, about his over sized 2 stage furnace.
    Thanks Beenthere - I think we're in violent agreement actually. Yes, I read Key1cc's thread back when it was active. Heat loads are calculated at a reference outside temperature, if the temperature falls below this reference, heat loss will be greater. While oversizing 2 stage equipment because installers are unable/unwilling to do a proper sizing calculation is bad, if the reference temperature heat loss lies between the two stages, that would appear to represent an ideal compromise between low stage comfort and high stage "reserve". Whether that's an 80,000BTU furnace or a 90,000 BTU furnace depends on the accuracy of the load calculation and the availability of sizes for any given manufacturer.

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