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  1. #1

    Carrier Furnace short cycling in a dual zone system

    Hi Fellas,

    I'm new to this site and I have a question that none seems to be able to answer. I have a dual zone heat/ac system in my 2100 sqft 2 story home. Recently my heater has been short cycling, but only when the heat is turned on up stairs. (Downstairs has been working great). When I say short cycling I mean I set the heat up stairs to 69 with the current temp 64. The heater will turn on and blow heat until it reaches 1 degree higher, then it shuts off and restarts. It will continue to do that until it reaches the set temp. So from 64 to 69 it shuts down and recycles 5 times.

    I have had a tech out who checked my zone control board and said it was bad. I replaced the board and get the same results. I have also tried replacing the electronic termostat with no luck. Filter is new and vents are up on the walls and clear.

    ANy suggestions? I'm out of ideas

    Thank you very nuch for taking the time to read this post.

    Mike

  2. #2
    Join Date
    Oct 2009
    Posts
    975
    The controls on the furnace are protecting you. A qualified tech can pinpoint why and then guarantee the repair.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,101
    Someone sharper needs to look at it. Find out what is shutting the furnace down. Could be overheating since only 1 zone is calling. May have been doing this since Day 1. What zone panel did you get? A good one these days will have a limit system to keep the furnace from cycling on furnace limit and it shuts the furnace down if the air gets too warm. Too many techs cannot properly diagnose an issue with a zoned installation.

  4. #4
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,660
    How many sq. ft. up? How many sq. ft. down? Does your zone system have a by-pass damper?

  5. #5
    BaldLoonie, Sweathog and George 2 thank you for the replies. I purchased a Robert Shaw slim zone classic. I installed it and it seems to be working well.
    George2 my home is 2098 sqft. I would guess the upstairs in 900sq ft and 1200 sq ft down stairs. I have replaced a honeywell spring acuated damper a year ago. I disconnected the honeywell unit and manually opened the butterfly to allow heat to the upstairs. Still no cahnge. I also just put in a newhigh limit switch with no luck.

    Mike

  6. #6
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,660
    Quote Originally Posted by Mike4435 View Post
    BaldLoonie, Sweathog and George 2 thank you for the replies. I purchased a Robert Shaw slim zone classic. I installed it and it seems to be working well.
    George2 my home is 2098 sqft. I would guess the upstairs in 900sq ft and 1200 sq ft down stairs. I have replaced a honeywell spring acuated damper a year ago. I disconnected the honeywell unit and manually opened the butterfly to allow heat to the upstairs. Still no cahnge. I also just put in a newhigh limit switch with no luck.

    Mike
    Okay, I thought maybe the upstairs was smaller area. I guess I should have asked how many supplies feed the 2nd floor?
    It doesn't sound like you have a by-pass damper. That HW spring damper goes where?
    I'm not clear as to what is still activated and what is disconnected?
    Are the registers in the floor or ceiling on the 2nd floor?

  7. #7

    I have the same issue

    Hi everyone,

    I have the exact same problem.


    Two story home, approx. 1600 sq. ft. upstairs, and 1500 sq. ft downstairs.

    2 zone control.

    Carrier Model 58 RAV
    115K BTU
    2000CFM

    Honeywell EMM-3 Minizone Controller
    White-Rogers 1F78 thermostat

    2 16" supply ducts into 2 J-boxes
    1 18" return duct
    11 in-ceiling registers upstairs various sizes
    9 in-ceiling registers downstairs various sizes

    PROBLEM: heater short cycles about every 7 min. (downstairs only)

    When heating downstairs only, error 33 high limit switch trips open. I measured the heat at the sensor, and it trips at 210F as designed, so I know my furnance is overheating.

    I can run the upstairs indefinitely, and the heater doesn't cycle.

    I believe I ruled out any electronic issues with the unit, and I believe that I may have airflow issues with the downstairs ducting.

    I have adjusted the upstairs damper to stay open about 30 degrees when I operate the downstairs control only. This has lengthen my cycle time to over 30 minutes ( I only tested to this time, as it may run longer before cycling)

    What else should I check? Would it be safe to operate given that I have adjusted the upstairs damper to get better airflow?

    Thanks!

  8. #8
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Thread relocated to AOP

  9. #9
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,101
    Your downstairs ductwork can't handle the entire output of the furnace. Opening the upstairs a bit is a wise move.

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