Results 1 to 11 of 11
  1. #1
    Join Date
    Jan 2007
    Posts
    20

    Quick cycling on Rheem mod

    I have a 1 month old Rheem mod furnace. During most evenings the furnace runs nearly continuously with very few cycles. However, about once or twice every evening I will near the t-stat click OFF only to turn back ON again after only 30 seconds and then run continuously for a very long time.

    Usually this happens when the t-stat shows we're near the setpoint. This caused me to believe it was an issue with the t-stat and not the furnace. However lately I have seen it cycle OFF then immediately ON again while it was doing recovery and about 2 degrees away from setpoint.

    Is it possible that this is the furnace causing this and not the t-stat? I thought the t-stat would click ON & OFF without any feedback or influence from the furnace. Is this correct? Or are there things the furnace can do that would cause a t-stat to click like that?

    If it is the furnace, shouldn't there be an error code generated on the Rheem's status LED? I tried looking thru the window at the LED and it always reads "0" = OFF or "H" = Heating. If there were a furnace error code related to this cycling, would it be displayed only while the condition existed then clear? Or is there a memory that would hold it so it could be discovered later?

  2. #2
    Join Date
    Jan 2007
    Posts
    20
    One further piece of information I forgot to add...

    To the best of my knowledge I have never observed this cycling behavior when the furnace is firing at 100%. I have only seen it happen when the furnace is firing at what seems like the 40% to 70% range.

  3. #3
    Join Date
    Jan 2004
    Location
    Here and there
    Posts
    4,804
    It's fine rest well. If there are no error codes and the set up is correct let it do its job. It should have a near constant run time when close to design temp . Is your house comfortable ? Does it reach set point ? As far as the stat clicking I have not a clue. Without a failure code it is tough to tell. Post the model and Serial # and venting configuration if you have doubts
    i belong to peta ... people eating tasty animals. all my opinions are just mine.

  4. #4
    Join Date
    Jan 2007
    Posts
    20
    Ok, here is my model/serial info...

    Model: RGFD07EMCKS
    Serial: FK5D702F490512785
    t-stat: TST401MDMS
    Venting: (I will try and go get a picture of it shortly)

    When the t-stat "clicks" OFF for 30 seconds to a minute then comes right back ON, the furnace actually shuts down completely then immediately re-lights. That does not seem normal to me. But I am suspicious that it's the modulating t-stat since I have already noticed so many problems with it (see the other messages I've posted regarding this).

    If the Rheem had generated an error code, for how long and under what conditions would that code be viewable on the LED? For example, if an error code was generated and the furance later re-lighted, would the furnace display "H" while heating or continue to display the actual error code? Or would the error code be lost forever (until it happens again)?

  5. #5
    Join Date
    Feb 2007
    Posts
    7
    Quote Originally Posted by BB1 View Post
    Ok, here is my model/serial info...

    Model: RGFD07EMCKS
    Serial: FK5D702F490512785
    t-stat: TST401MDMS
    Venting: (I will try and go get a picture of it shortly)

    When the t-stat "clicks" OFF for 30 seconds to a minute then comes right back ON, the furnace actually shuts down completely then immediately re-lights. That does not seem normal to me. But I am suspicious that it's the modulating t-stat since I have already noticed so many problems with it (see the other messages I've posted regarding this).

    If the Rheem had generated an error code, for how long and under what conditions would that code be viewable on the LED? For example, if an error code was generated and the furance later re-lighted, would the furnace display "H" while heating or continue to display the actual error code? Or would the error code be lost forever (until it happens again)?

    bb1, mine does the exact same thing,i believe it's the stat. as far as the error codes it would be stored so if you want to find out if you have any codes stored, power down the furance then wait a few seconds and power it back up and watch your code display window sequence the error code #'s if any show up. for instance 8 followed by 2 will be error code 82...

  6. #6
    Join Date
    Jan 2004
    Location
    Here and there
    Posts
    4,804
    Modman is correct. Fault codes will be stored from latest to oldest. The reason I ask about the vent is that it is critical and the biggest problem with this series and most others is drain and vent. Drains plug at the traop and other places. The vent on this furnace is very limited in length for 2 " even though the connestions are as such.
    i belong to peta ... people eating tasty animals. all my opinions are just mine.

  7. #7
    Join Date
    Apr 2004
    Posts
    7,680
    are you sure it's set up to modulate? (valid V signal). When you mention 40 and 70 this leads me to believe they didnt hook the V wire up correctly...

    Is there a capitol H in the Window during a call for heat or is there a lower case h?

    You may also want to make sure thre are no offsets in the ambient temperature.

  8. #8
    Join Date
    Jan 2007
    Posts
    20
    Yes, the V wire is hooked up. And yes, it displays a capital "H" on the furnace LED. I don't have an offset set.

    I know it is modulating since moving the setpoint up will immediately cause the furnace to start firing harder and then lowering the setpoint back down will immediately cause it to fire less.

    When the furnace is not receiving the V signal it uses a blind timing method which is incapable of responding to setpoint changes in the manner described above. Therefore I am certain it is operating in modulating mode.

  9. #9
    Join Date
    Mar 2007
    Posts
    3
    Not to hijack your thread, but this is what I am concerned about while getting quotes for a new system. Does anyone know if the Focuspro6000 or 8000 will show the error codes on this type of furnace? My contractor wants to use these instead of the Rheem touchscreen. He said they use them all the time.

  10. #10
    Join Date
    Apr 2004
    Posts
    7,680
    Then he's ignorant, the Honeywell stat cannot operate the mod furnace in modulating mode. The WR thermostat has a 5 year warranty, if there is a problem you are covered.

    This individuals problem merely needs to be looked at, yeah it could be a bum stat but it could be a hole in the wall behind the thermostat, or one of a few other things. If the contractor is still trying to figure out the problem he should call his distributor's service manager for some help. The funace doesnt make any thermostat "click". This is a function of the thermostat itself.

  11. #11
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    Quote Originally Posted by Spanky1 View Post
    Not to hijack your thread, but this is what I am concerned about while getting quotes for a new system. Does anyone know if the Focuspro6000 or 8000 will show the error codes on this type of furnace? My contractor wants to use these instead of the Rheem touchscreen. He said they use them all the time.
    If you are getting a Mod furnace be sure you get a matching MOD t-stat.. You are spending good money on this fine piece of equipment, no point of crippling this with a 2 stage t-stat where the Mod stat will do 13 stages.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event