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  1. #1
    Join Date
    Feb 2004
    Location
    Tucson AZ
    Posts
    55
    Does anybody know where I can get some information that will help explain how oversizing a mid efficiency gas furnace will waste more energy than a properly sized unit? Thanks in advance for any help.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,396
    Not sure where you will see it in writing but it's the same as a car driving fast and hitting red lights vs running slower and making the lights. Accellerating chews up gas vs running steady. Same with a furnace. The first 5-10 minutes of a burn cycle isn't near full efficiency so if you have a larger than necessary unit cycling more, much more of its time is spent below peak efficiency. A smaller furnace running longer will spend more time at full efficiency.

  3. #3
    Join Date
    Feb 2004
    Location
    Tucson AZ
    Posts
    55
    Thanks Loonie, I am familiar with why oversizing is less efficient, unfortunately I installed a furnace for a customer last month. She had no complaints from her tenant after the installation but she had a plumbing and heating contractor come in to bid running a gas line. This guy took it upon himself to tell the home owner that the furnace was too small and it would cost more to operate. I have talked to the customer who I am unable to get thru to but she somehow feels I sold her to small of a unit. I would appreciate if any one knows of any articles from publications on this subject.

  4. #4
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    I agree with Bald on this..

    Another way to look at is, this.. In a mid sized car. What one is going to get better gas mileage?

    A V-10 vs a 4 cylenders?


  5. #5
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,373
    Strangle that plumber/heating guy!

    You should have done the gas piping!

  6. #6
    Join Date
    Jul 2005
    Posts
    717
    [QUOTE]Originally posted by mayguy
    [Another way to look at is, this.. In a mid sized car. What one is going to get better gas mileage?

    A V-10 vs a 4 cylinders?
    ************************************
    Yes, but when the hills get steeper, guess what car is going to bog down and wear out and/or start lagging,while the big, powerful one with 5 passengers and a trunk load of heavy stuff just keeps going and going.

    And this applys to a well calculated, over sized furnace that will cycle less per hour while maintaining the T stat setting,at the outdoor design temp while the the other smaller unit just keeps running and running and prematurely wearing out many$$$$ parts etc,(not to mention the high price of the service calls,etc) just for the sake of saving perhaps a couple bucks worth of fuel per month.

  7. #7
    Join Date
    Jul 2004
    Location
    midwest
    Posts
    2,868
    Deejoe is loose again. Someone please tie him up.

  8. #8
    Join Date
    May 2003
    Location
    Dover, DE
    Posts
    38
    So did you do a heat loss calculation? Without it I would be in doubt as well. With it you can prove you sized it correctly. You might ask if that plumber did a heat loss as well.

    Does everbody now use their eyeballs to size HVAC equipment these days?

  9. #9
    Join Date
    Jul 2005
    Posts
    717
    Originally posted by trane
    Deejoe is loose again. Someone please tie him up.
    -------------------------------------------------
    The truth must hurt ,eh?

    And one thing is for sure that it won't be you that will tie me up because you never did learn to tie a knot (LOL)

  10. #10
    Join Date
    Feb 2004
    Location
    Central Kansas
    Posts
    1,145
    Show her the math- your heat loss/gain calculations. Don't badmouth the plumber, but ask if he did any specific calcs or just guessed. Give her some names of happy customers whom you've removed an oversized gas hog and put in a lean, mean heating machine. Unfortunately all it takes is some idiot to throw doubt in your customer's mind and you're made out to be the bad guy. I believe the satisfied customer referral will help out most. Especially if you have one as I do that virtually told me to leave and not come back until I had a 'real' furnace in hand. It took some more convincing, but made a believer out of him.

    I've probably lost as many sales due to price as I have because 'so-and-so company' said I was going to install too small a system. But, I sleep well knowing that I do more for area consumers regarding energy savings and comfort than 4 out of 6 competitors... and I work for the gas company!
    Don't confuse me with facts, my mind is already made up.

  11. #11
    Join Date
    Jul 2004
    Location
    midwest
    Posts
    2,868
    Originally posted by deejoe
    Originally posted by trane
    Deejoe is loose again. Someone please tie him up.
    -------------------------------------------------
    The truth must hurt ,eh?

    And one thing is for sure that it won't be you that will tie me up because you never did learn to tie a knot (LOL)
    You have yet to see the truth.

  12. #12
    Join Date
    Feb 2006
    Posts
    3
    well i agree with BaldLoonie and if your customer is a woman she will think bigger always better. as long as sq ft of house matches size of unit or 1/2 size bigger you did right thing.compare a four cyclinder to an eight on the same car.are you looking to save money or go faster. but in ac, unless duct work is changed you will not push that much more air. but question is how much money can you spend now that can save you lot of money in a few years or how cheap do you want to pay now but will be more expensive in a few years. some of us can not afford 2 stage with verible speed blower that run about$8,000 and up.alabama

  13. #13
    Join Date
    Jul 2000
    Location
    Louisiana , USA
    Posts
    3,280
    Originally posted by sayco bob
    Thanks Loonie, I am familiar with why oversizing is less efficient, unfortunately I installed a furnace for a customer last month. She had no complaints from her tenant after the installation but she had a plumbing and heating contractor come in to bid running a gas line. This guy took it upon himself to tell the home owner that the furnace was too small and it would cost more to operate. I have talked to the customer who I am unable to get thru to but she somehow feels I sold her to small of a unit. I would appreciate if any one knows of any articles from publications on this subject.

    This is Turtle.

    Here is a major gas company telling you it cost more to have a too big of a furnace.

    http://www.socalgas.com/residential/.../heating.shtml

    Then look under section """ Appliance Selection Tips """ to read about too big of a furnace will cost you more to run the system.

    Now if there is any question here BaldLoonie nailed it.

    TURTLE

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