Results 1 to 12 of 12
  1. #1
    Join Date
    Oct 2006
    Location
    Chicago
    Posts
    4
    I am currently shopping for a new furnace and got four estimates. I have a 2000 square foot 2 story home with a full basement which is 1/2 finished. The 2000 does not include the basement. The home is 15 yrs old and is insulated and sealed pretty good.

    Here is my dilema. I am look for a 2 stage 90% + efficient furnace. My current furnace shows a BTU of 115,000. Two estimates came in with 100,000 BTU, one 80,000 BTU and another 70,000 BTU. The guy who quoted the 70,000 said the current furnace is too big, short cycling, and everyone is going off the current furnace size. I have seen the furnace turn on and off a few times within a few minutes but not all the time. I mentioned this to one guy who quoted me for the 100,000 and he said that the size of my house requires a 100,000.

    Can anyone help me in determining which is the best furnace for my home?

    Thanks for any advice you can provide.
    Wingmann

  2. #2
    Join Date
    Dec 2005
    Posts
    117
    Well, it depends on where your house is located. A 2000 sq ft house in FL will need very little heat, while a 2000 sq ft in MN will need alot more heat.

    What you need is a heat loss calc. Either ask your contractor to do this, or do one yourself. You can get the software for free from Slant/Fin (heating only), or somewhere on this site is a link to a different program for $50 (heating and cooling).

    No one can say for sure over the internet, but my feeling is the 70,000 BTU is the proper choice.

    For comparison, my brother's house in SE WI is a 10 year old, 2000 sq ft ranch with 1/2 finished basement. He has a 60,000 furnace.

    Michael

  3. #3
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,234
    Originally posted by wingmann
    I have a 2000 square foot 2 story home with a full basement which is 1/2 finished. The 2000 does not include the basement. The home is 15 yrs old and is insulated and sealed pretty good.

    I am look for a 2 stage 90% + efficient furnace.

    Can anyone help me in determining which is the best furnace for my home?
    Chicago Heating Degree Days Annual ~ 5,800
    HDD Max. Monthly 1,200

    Post Monthly fuel consumption for Oct - March
    for the last 3 years.

    W.A.G.
    #1 Furnace size needed 80,000 BTUh at 90%
    if you wish to maintain 70'F when it is 0'F.

    #2 100,000,0000 BTUh needed for annual heating.
    __ 1400 Therms ($1,600 )
    __ with an existing 70% furnace efficiency.

    ........................
    Or perform Manual J calc

    # windows __ ( 16?)
    Total Area ___ ( 240 Sq.Ft ?)

    R-value ceiling ____
    R-value walls ______
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  4. #4
    Join Date
    Apr 2006
    Posts
    143

    2 cents

    I might get jumped on for this by another tech, but you should know it is possible to de-rate a new 100,000 btu furnace to 70,000 btu by closing up an orfice or two if after install the new furnace is short cycling

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,712
    You'd have to relocate the flame sensor.

    Lose the warranty on the new furnace.

    Its also alot easier to put in the right size, instead of screwing around trying to make an over sized furnace the right size.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Mar 2005
    Location
    South/West of Quebec in the other part of Canada
    Posts
    2,331
    Originally posted by wingmann

    Can anyone help me in determining which is the best furnace for my home?

    Thanks for any advice you can provide.
    Wingmann
    I am going to guess that you are quit northern in local...judging by the sizes you have been quoted on.

    However, you want to do business with a company that will provide you with a heat-loss, so that the system installed, will perform properly.

    I live up in Canada eh! and in most cases were I live, a house 2000sq.,10 year old with 2x6 wall construction a 70Kbtu would do the job.

    P.S. make sure a 2 stage thermostat is installed.

    P.P.S. as for 4 estimates, you are now wasting your time and the contractors...choose the contractor that will work for you, don't shop price...shop contractor.

  7. #7
    Join Date
    Aug 2002
    Location
    manitowoc wisconsin
    Posts
    4,943
    If you are not going to do a heat load calculation the guy that quoted the smallest furnace is more than likely the closest to your needs.
    Take your time & do it right!

  8. #8
    Join Date
    Feb 2003
    Location
    S.W. PA
    Posts
    3,298

    Re: 2 cents

    Originally posted by ddog1
    I might get jumped on for this by another tech, but you should know it is possible to de-rate a new 100,000 btu furnace to 70,000 btu by closing up an orfice or two if after install the new furnace is short cycling
    I won’t jump you but would love to see from a reliable source where this is acceptable

    I have never been able to find anyone that would put their neck on the line over de-rating a furnace at least anyone that would take my neck off the chopping block if something goes wrong

  9. #9
    Join Date
    Oct 2006
    Location
    Chicago
    Posts
    4
    Thanks for all the help everyone. I live in Chicago, have 16 windows, total square footage of the home would be 3000 sq feet including the basement. I believe the ceiling insulation is an R39. Unfortunately I don't know the R rating for the walls but can say that new siding was installed this year and small foam insulation sheets were installed over the existing Tyvek before the siding was installed. The contractor who qouted me the 70,000 BTU unit did mention he performed some type of calculation. Just an FYI, I am done with obtaining estimates and now am trying to figure out which is the best furnace to pick. The brands are York, Bryant, Carrier and Rheem.

    Wingmann

  10. #10
    Join Date
    Feb 2003
    Location
    S.W. PA
    Posts
    3,298
    Well call all the contractors back and ask them how they came up with the size you needed
    Anyone who says square footage or I just know cross them off the list
    The only acceptable answers are
    1. we did or will do a heat loss calculation
    2. because when we did you neighbors house which is identical to your house in everyway shape and form (not likely) the HEAT LOSS CALCULATION told us that was the size
    3. you may also hear they used a manual J this is the correct way just a different name



    Now if none of the contractors do this then you may want to question what else they don’t do right

    The best advice anyone here can give you is to find the right contractor
    If the furnace is not installed right you wont get the efficiency, life span, reliability, and possibly warranty
    So make sure you get the job done right


    As some of the others here have mentioned you can do your own heat loss calculation but why would you want to? This is something that should be taken care of by whoever you choose to install the furnace

  11. #11
    Join Date
    Oct 2006
    Location
    Omaha, Nebraska
    Posts
    67
    Well Judging by the size of your house, if you take the square footage of 2000 times a multiplier, you will come within 2000 BTUs of what you need, taking this by the multiplier you will need approximatly 91,300 BTU's of output, and normally this will work if your windows are sealed and do not leak and if your house is well insulated and also what direction your house faces. To be honest with you we have been very acurate when compared to an extensive load calculation. I hope this helps you with your question.

  12. #12
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    The 70k sounds with in range, no more than 80k. Download your own HVAC Calc above for $50. and you can see where you are sitting at.

    Are you doing variable speed as well? Make sure you do get a two stat t-stat.

    In my own home, I had a old 115k, and been replaced with a 60k two stage. It kept up very well last winter when we had a cold snap of -22 degree.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event