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  1. #1

    Explain this please

    2 rent houses.

    Same size AH (3 ton) and 10kw heat.

    One rent house a 1993 Bryant, 70 amp breaker

    Other rent house 2011 Goodman, 60 amp breaker

    Similar sq ft, 1348 sq ft and 1377 sq ft

    Very similar ductwork layout, same amount of vents, similar size vents.

    The Bryant house the heat blows 35 degrees warmer (when compared to the return air at grill) air from the vent closest to the plenum.

    The goodman house blows at most 27 degrees warmer (when compared to the return air at grill) air from the vent closest to the plenum.

    Ok i asked the hvac guy i use (young guy just started his business in last year or so) how is this possible. His reply was he thinks the older bryant unit heater coil gets hotter. Sounds like bs to me, can someone more seasoned in the heat/air business render an opinion?

  2. #2
    Join Date
    May 2001
    Location
    carthage ms
    Posts
    632
    Air flow and fan speeds effect temp rise also the older machine could have a dust build up on the coil or blower wheel reducing the air flow and increasing the temp rise
    The 2008 NATE TOP TECH!!!!!

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,112
    Can't tell for sure from here.

    Could be the newer system isn't charged right. Or it may be moving more air then the older system.
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    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    entirely too little info,

    was this with the h/p & aux. heat or h/p only, or aux. heat only???????????
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  5. #5
    straight heat, not a hp

  6. #6
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,002
    Quote Originally Posted by hvacman14 View Post
    Air flow and fan speeds effect temp rise also the older machine could have a dust build up on the coil or blower wheel reducing the air flow and increasing the temp rise

    This
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

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  7. #7
    ok so it would be totally ignorant to say because one is on a 70 amp breaker and one is on a 60 amp breaker that the 70 amper 10kw heat would run hotter? Thats basically what this guy is saying which didnt sound right to me. Am i right in thinking this way? 10kw heat is 10kw heat in any case, correct?

  8. #8
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    1,048
    Quote Originally Posted by Old Man Kenneth View Post
    10kw heat is 10kw heat, correct?
    correct.

  9. #9
    Join Date
    May 2001
    Location
    carthage ms
    Posts
    632
    10 kw is 10 kw no matter how you figure it, but, the temp rise air flow formula will equate to the rated kw, the older unit can run hotter if the air flow is lower than the other system that it is being compared to, and still produce the same kw
    The 2008 NATE TOP TECH!!!!!

  10. #10
    Join Date
    Sep 2004
    Location
    Jersey
    Posts
    389
    air flow sound like the issue, or maybe a bad heat strip coil. lack of info to tell.
    Ride hard on a Harley!!

  11. #11
    Join Date
    Sep 2004
    Location
    Jersey
    Posts
    389
    on the breaker is it in the electric panel or on the heaters, it could just be what the manufacture requires. you can get the same tonnage condenser and have a different amp draw all depends on what it is spec out to
    Ride hard on a Harley!!

  12. #12
    Join Date
    Jan 2009
    Location
    Central Iowa
    Posts
    213
    10000watts/220volts = 45.45 amps.
    This is what the heater will draw. The breaker size will not change this. The other things drawing amperage in the air handler are the blower motor and the control transformer.
    Your young guy should be able to check running amps on both heaters, and I mean heaters only, not the whole unit, and tell if they are drawing full load amps. If one is NOT pulling about 45 amps, part of the heater strips are out.
    Simple as that. I hope this helps.

  13. #13
    Join Date
    May 2008
    Location
    Central Fla.
    Posts
    311
    10 KW is NOT 10 KW as a blanket statment. It is dependent on your line voltage to the heat strips. If one system has 248 v a/c and the other has 218v a/c they will put out different amounts of heat if all else is equal. Sounds more like a return air leak(pulling in cold attic air causing it to drop the temp coming out a vent) if the voltages are the same.

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