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Comfort aire beckett oil furnace (uni oil) short cycling when thermostat is not calling for heat???

rmb551
rmb551 Member Posts: 7
in Oil Heating
It is turning on and runing the burner, then shutting off b4 the fan comes on, then it will do it again 10 minutes later! The thermostat is not calling for heat! I have replaced the t-stat, the wiring between t-stat and furnace, the limit switch, and both the relay and transformer on fan center!!! Im at a loss, what is "sticking" or "malfunctioning" turning the burner on when the t-stat is not calling for heat??? Ive been thru the wiring schematics dozens of times and checked connections! Could the oil burner control(grey box with reset button) be malfunctioning and turning on intermittantly or the relay going to it??? 

Comments

  • Big Ed_4
    Big Ed_4 Member Posts: 2,935
    I have not seen the burner primary turn the burner by itself . I assume the thermostat is connected to a board or a fan center . You will need to test the system to find the problem . Disconnect the thermostat at the unit .If it stops then it is a problem from there to the thermostat . If it still act up disconnect the TT at the primary control and see what happens . If there is a jumper across TT I would suspect the fan center or board...

    There was an error rendering this rich post.

  • rmb551
    rmb551 Member Posts: 7
    Fan center is new, thermostat is new, wiring between t-stat and fan center-new, there is no control board(too old),limit control-new. Only things I have not changed are primary control(grey box with reset) and the isolation relay(going to tt) So what I am asking is could one of those 2 things be malfunctioning and turning burner on when nothing is calling for heat? 
  • SuperTech
    SuperTech Member Posts: 2,266
    The grey box, R8184G burner control is a piece of junk that should be replaced even if it's functioning correctly. Those controls are antiquated technology that energizes the ignition system the entire time the burner is running. It's like holding a lighter up to a candle that is already lit. Try installing a modern Carlin primary control and set it up for interrupted ignition. The diagnostic features on the Carlin can be useful when troubleshooting. 
    EdTheHeaterMan
  • HVACNUT
    HVACNUT Member Posts: 6,073
    I can't see the N.O. isolation relay magically open and close by itself, then TT on the primary can't close. 
    Can you show the wiring or draw a diagram?
  • Big Ed_4
    Big Ed_4 Member Posts: 2,935
    Did you leave a section of old thermostat wiring ?

    There was an error rendering this rich post.

  • rmb551
    rmb551 Member Posts: 7
    Wiring is completely new(used old wire to pull new wire) I have Identical furnace in garage(its a Ruud not a unioil) but all parts are same exact part # so far, so pulled both those from it, trying grey box now, if it doesnt Ill  put relay in(doing 1 at a time so I can find this ****!) And I have another t-stat that I can try(cause new doesnt always mean good) Bad thing is If I had a tech come, whats he gonna do  sit here til it just randomly comes on! It did it  twice  6-7a.m. and hasnt done it since!Trying to get it sorted b4 it gets cold! If something fixes it I will post what it was! 
  • rmb551
    rmb551 Member Posts: 7
    P. S. I have the schematics and cant find any wiring screw ups! Everything looks correct! 
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,638
    edited October 2023
    You will need to provide more information. If I said that my car was accelerating by it self for 10 seconds and then goes back to normal to a auto mechanic, and ask "What could cause that?" they would not be able to tell me what is wrong with only that information. The first round of questions would be , Year, Make, Model, What transmission, What engine. So far all I know is that your have one of several Beckett burners on a Comfort air furnace. It is more than 10 years old because it has the gray box primary control. Need more info. Or you could just fire the parts cannon at it. Oops you already did.


    I am not Carnac the Magnificent so I can only guess that there is an older ST9103A fan timer and someone has mis-wired that control when attempting to replace another control. The normal control diagram for the R8184G for example, May not be the correct method when matched with the ST9103A fan timer. Those ST9103A controls have had their issues also.

    Can you provide the model and serial number of your furnace and approx. age. And perhaps a picture of the place where the thermostat wires connect (sometines in the blower compartment) and a picture of the oil burner so I can see the label on the back of the burner, just below the RW Beckett sticker. That shows the components that burner was built with, the firing rate and sometimes the recommended nozzle spec.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • Big Ed_4
    Big Ed_4 Member Posts: 2,935
    Disconnect the thermostat at the unit and see what happens , No short cycle,,,,,, the problem will be the thermostat circuit ....

    There was an error rendering this rich post.

    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,638
    rmb551 said:

    P. S. I have the schematics and cant find any wiring screw ups! Everything looks correct! 

    "Everything looks correct!"...and yet, you are having this problem. What does the back of the circuit board on the fan control look like? Are there any loose solder joints.

    Are these schematics top secret papers? I promise not to sell them to the Russians if you show them to me.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HVACNUT
    HVACNUT Member Posts: 6,073
    edited October 2023
    Unless something was rewired, the only thing that starts that burner is closing TT on the primary. The only way TT closes is through the isolation relay. The only way the contacts on the isolation relay close is if there's 24 volts to the relay coil.
    Is anything connected to W on the Fan center other than W from the thermostat? Is there a Humidifier or dehumidifier?
    What make and model thermostat?
  • pecmsg
    pecmsg Member Posts: 5,121
    What make thermostat?
  • rmb551
    rmb551 Member Posts: 7
    It is a 1996 here are your pics, it "ghosted" twice around 6-7a.m. on the 20th... Did it again on 21st around 8p.m. I pulled the thermostat (honeywell rth110b)off to make sure it wasnt turning it on without saying "heat on" (because new doesnt always mean " good") it kept running, while not calling for heat! I ran downstairs to check more, but it stopped!!! Now have to wait for it to do it again... 
  • rmb551
    rmb551 Member Posts: 7

  • rmb551
    rmb551 Member Posts: 7
    Sent wiring again , cause first one was cut off!!!!!!!

  • pecmsg
    pecmsg Member Posts: 5,121
    If the control wires are solid those are the wrong connectors. 
  • HVACNUT
    HVACNUT Member Posts: 6,073
    That's a pretty cheap thermostat. Dust? Blow it out. Make sure wires can't touch each other. 
    How cold is it? Can you leave the thermostat off the sub base for a few days?

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