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Thread: TStat ?

  1. #1
    Join Date
    Feb 2005
    Posts
    12
    I have a 93% efficient furnace and 14 seer AC unit. Everyting seems to work fine but my furnace only runs 3-5 minutes at a time it does maintain the 70 degrees set on the furnace no problem. I have a Honeywell Chronotherm 111 thermostat. I was told it really causes the furnace to cycle to frequently. Any suggestions on a Tstat for this. It appears White Rogers Tstats will let you adjust temperature variance which will let the furnace burn longer. It seems to me the furnace is not near as efficent when it only burns 3-5 minutes. Just when the ductwork etc is warmed up it shuts down. Maybe I am wrong. Your thoughts will be greatly appreciated.

  2. #2
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by hageman6
    I have a 93% efficient furnace and 14 seer AC unit. Everyting seems to work fine but my furnace only runs 3-5 minutes at a time it does maintain the 70 degrees set on the furnace no problem.
    Your furnace looks oversized from here. Was a heat loss calculation done when it was installed?

  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,317
    The cycle rate for high efficiency furnaces on Honeywell stats can differ from the normal setting. Have your installer read the thermostat's installation literature to ensure which cycle rate is best for this system.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    Feb 2005
    Posts
    12
    Yes the heat calc was completed. I had a 100BTU 80 percent that when operating really kept the house comfortable. The new 93 Percent efficnet furnace is an 80K based on the heat calc.

  5. #5
    Join Date
    Nov 2002
    Location
    Albuquerque, NM
    Posts
    35
    I had a Honeywell T8000C Tstat installed with a new Carrier 58CVA furnace. The default cycling rate on the thermostat was 6 cycles per hour, while the furmace manual called for 3 cph. You need the tstat installation manual to know how to reset the tstat cycling rate. The owners manual doesn't have it! I reset it and it's much better. Obviously at 6 cph it's going to be cycling every 10 min which is annoying.

  6. #6
    Join Date
    Jan 2005
    Posts
    340

    Cycle Rate adjustment on Chronotherm III


  7. #7
    Join Date
    Feb 2005
    Posts
    12
    Thanks for the installation guide. It appears that this adjustement should take care of my problem.
    Thanks

  8. #8
    Join Date
    Jan 2005
    Posts
    340

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