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Thread: Short cycling

  1. #1
    Join Date
    Sep 2003
    Location
    Ocean County, N.J.
    Posts
    477
    Got a " short cycling " call yesterday. Brand new 1950 sq. ft. home in a gated adult community. Furnace was a Goodman GMS90453BXA, t/stat Honeywell programable { found absolutely nothing wrong with either one }. O.D. temp 30 degrees. I.D. t/stat set point 65 degrees. Furnace runs for six minutes, off for three, and this cycle just keeps repeating. I'm sorry if I didn't mention that the system is maintaining the t/stat set point, and when the furnace cycles off { for 3 minutes }, it's because the t/stat has satisfied. What would you have done? Is anything actually wrong? I'll read some of your posts and then tell you {right or wrong} how I wrote the invoice and billed this call out { regular service rate }. I'm trying to see if I did the right thing.

  2. #2
    Join Date
    Jul 2005
    Posts
    717
    it could be the Tstat's "cph" setting needs adjustment due to a 'slipped/loosened rotator screw'.
    what type ,model is this t stat?
    Some ,(not all) can be adjusted.
    Some need to be thrown away and replaced.

  3. #3
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    alot of honeywell stats have a screw or dip switch on the back the need to be set for high eff units

    this alows them to be universal to all systems

    change the settings and it should make a differance

  4. #4
    Join Date
    Sep 2003
    Location
    Ocean County, N.J.
    Posts
    477
    Thanks for your responses. How many cycles per hour are we looking for with 30 degree O.D. and 65 degree I.D. set point? It is a 45,000 B.T.U. hi efficiency furnace in a 1900 plus sq. ft. home. Again, how many cycles per hour are we looking for?

  5. #5
    Join Date
    Jan 2006
    Posts
    214
    i wonder if a load calc was ever done 45,000 btu furnace with a nearly 2000 sq ft home?sounds a little undersized.

  6. #6
    Join Date
    Sep 2003
    Location
    Ocean County, N.J.
    Posts
    477
    jeffshvac no arguement from me on the sizeing, but I'll repeat the question: how many cph are we looking for?

  7. #7
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    that would pepend on the house and the loss
    there is no set rate that can be given with out this info


  8. #8
    Join Date
    Jan 2006
    Posts
    214
    i would look for 4-5 cph but it could vary.

  9. #9
    Join Date
    Dec 2005
    Location
    Canada
    Posts
    61
    3CPH is the general opinion of many on this board.

    Having said that it does not mean much if furnace is not sized correctly. IMHO

  10. #10
    Join Date
    Jan 2006
    Posts
    214
    3 cph is ideal but with an undersized furnace its not realistic. jmo thanks

  11. #11
    Join Date
    Apr 2005
    Location
    Kingston Ontario Canada
    Posts
    1,211
    Originally posted by jeffshvac
    i wonder if a load calc was ever done 45,000 btu furnace with a nearly 2000 sq ft home?sounds a little undersized.
    Certainly does sound undersized. A furnace that small in a 2000 sq ft home should be running almost all the time, right?

    Thorton

  12. #12
    Join Date
    Jan 2006
    Posts
    214
    im sure everyone in this gated community got an undersized furnace this is what happens when a builder takes the lowest bid and the contractor installs the bare minimum equipment.the only people that suffer are the homeowners.and it figures they each got a goodman.jmo thanks

  13. #13
    Join Date
    Sep 2003
    Location
    Ocean County, N.J.
    Posts
    477
    I agree with all of your posts. I wrote on the service invoice:" Checked t/stat and furnace, found both to operating normally. No further diagnostics possible until load calculations have been performed." Articulating the invoice in this way I felt I was not entering an opinion either way, but pointing out a foundation had to be established before you could go foward. Having said that, for my own information can anyone tell how to adjust the CPH on a Honeywell T812D t/stat?

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