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Trane package unit 2 stage gas valve adjustment

Does anybody know how you adjust the low fire on this valve? There is an adjustment screw under the cap I have been able to set high fire but don’t see where you adjust low at. Just replaced a sooted up heat exchanger on this unit I imagine was caused by the high gas pressure settings in low and high fire.  It’s a model 36c76 type 486. The black cap on the side is the vent. It’s on a Trane ysc092a3rma29a

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,913
    edited January 2021
    Have you checked the operating gas pressure on the manifold side of the gas valve?
    Does this unit have an exhaust vent fan? Check to see if the fan failed after some time and the burner is still firing. That may cause carbon buildup
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • ratio
    ratio Member Posts: 3,331
    Looks like a White Rodgers valve. Have you looked through their literature for a similar valve?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,096
    Is this one of those Roof tops with the power burner where they use negative gas pressure on the outlet side of the valve? If so there are some videos on U tube about that
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,096
    From what I could find the two stage valves have two adjustment screws on top 1 for lo and 1 for high
  • thegreatcornholio
    thegreatcornholio Member Posts: 25
    Is this one of those Roof tops with the power burner where they use negative gas pressure on the outlet side of the valve? If so there are some videos on U tube about that
    No it’s not one of those it’s just like a normal 80% gas furnace. It’s 2 stage but can’t see where low fire adjust is located
  • thegreatcornholio
    thegreatcornholio Member Posts: 25
    ratio said:
    Looks like a White Rodgers valve. Have you looked through their literature for a similar valve?
    Yeah looked all over online and in the Trane installation manual
  • thegreatcornholio
    thegreatcornholio Member Posts: 25
    From what I could find the two stage valves have two adjustment screws on top 1 for lo and 1 for high
    Do you see it in the picture?
  • thegreatcornholio
    thegreatcornholio Member Posts: 25
    Have you checked the operating gas pressure on the manifold side of the gas valve? Does this unit have an exhaust vent fan? Check to see if the fan failed after some time and the burner is still firing. That may cause carbon buildup
    ...I guess re read my post?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,096
    @thegreatcornholio

    I spent some time searching for that valve with no luck. I think it may be an OEM valve made for Trane.

    I suspect lo fire is non adjustable but that is just a guess.

    Maybe post the RTU model # and we can find it through Trane


    Hate OEM stuff
  • thegreatcornholio
    thegreatcornholio Member Posts: 25
    @thegreatcornholio I spent some time searching for that valve with no luck. I think it may be an OEM valve made for Trane. I suspect lo fire is non adjustable but that is just a guess. Maybe post the RTU model # and we can find it through Trane Hate OEM stuff
    Yeah I’m thinking there is just no adjustment for low too..pretty weird.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,096
    I found the manual on line. For two stage all it says is 1.8" wc for low fire and 3.5" wc for high fire that's what it says to set it to. No pictures of the gas valve or how to adjust.

    I know a guy that works for Trane if I still have his # I will reach out. Bad instructions piss me off.