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Thread: montague oven

  1. #1
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    montague oven

    hey guys im still learning the kitchen field i have been in the hvac-r field for 5 years but just started doing kitchen equipment well im working on a montague oven keep having this issue where the pilot light keeps turning off thermocouple has been replaced also safety valve where the thermocouple goes to the weirdest thing is that pilot stay on as long as the oven is not being used but as soon as they start using it it stays on for like 30 min then it turns off m#2-115a(s) any input would really be appreciate thanks. oh yea there are also 3 other ovens of the same gas line and they are working just fine.

  2. #2
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    The ovens might each have dedicated gas line regulators and the one for that oven may be on the fritz.

    I suggest checking gas pressure to that oven. It may be dropping too much during main burner demands. That will cause a less intense pilot flame and eventually slowly lower the thermocouple output to below the lockout threshold of the pilot safety valve.

    I also recommend ensuring the thermocouple is properly and securely installed into the pilot burner bracket. Here's why:

    Although it's in the oven and gets very hot, only the last 1/3 of the thermocouple should get RED hot. That last 1/3 is the hot junction. Conversely, where the compression collar nut is - is the cold junction. The difference in temperature between those two points gives you your DC output.

    The compression collar also serves as a heat sink for the cold junction and will dissipate heat to the pilot bracket and the heat shield that IT'S mounted to.

    If the thermocouple isn't securely mounted, then it can't dissipate the heat from the flame as readily, so the cold junction will retain that heat, get much hotter and thereby weaken the effective output of the thermocouple. Depending on the conditions, it may drop low enough to cause the pilot safety valve to lock out.

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  4. #3
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    Thanks for the input and yes each oven has its own regulator so i will check the gas pressure and i did check thermocouple and its in the right spot and secure so my next step will be to check the gas pressure to it.

  5. #4
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    Make sure your thermostat bypass setting is ok. It might be going out and popping when coming back on, blowing out the pilot. Sound about the right timing, 30 minutes, for that to happen.

    Has someone replaced the thermostat recently?

  6. #5
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    Quote Originally Posted by BadBozo2315 View Post
    Make sure your thermostat bypass setting is ok. It might be going out and popping when coming back on, blowing out the pilot. Sound about the right timing, 30 minutes, for that to happen.

    Has someone replaced the thermostat recently?
    Great points. That's certainly at the top of the list as one of several issues caused by improper installation of modulating thermostats.

  7. #6
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    no thermostat has not been replaced i would of never thought that the thermostat would take a pilot out and it seems to get to temp right but it wont stay there because the pilot goes out.

  8. #7
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    Low gas pressure can also cause delayed ignition, causing the pilot to go out. Plugged regulator vent plugs are the most common issue. Check thermocouple output by disconnecting from pilot safety, and read between the disc at end of TC, and the outer copper tubing, with meter on millivolts DC. Should be about 20-30 mV no-load.(you have to hold the safety valve in for this, and be sure the thermostat is off). Then check burner venturi and orifice for restriction.

  9. #8
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    Quote Originally Posted by neto23 View Post
    no thermostat has not been replaced i would of never thought that the thermostat would take a pilot out and it seems to get to temp right but it wont stay there because the pilot goes out.
    The issue that Badbozo was suggesting can arise from the thermostat is this:

    It's a modulating thermostat. Its span of operation ranges from 100% gas flow to the burner (a full flame, such as when an oven is first turned on) and incrementally down to the bypass flame (when thermostat is satisfied and has throttled down to 0% output).

    When a BJ or FDO thermostat is properly installed and set up, it should have a bypass flame of about 1/8" high. Any MORE and the oven temp may continue to rise even though the thermostat is satisfied. Any LESS and the main burner flame may go out completely.

    The problem with the latter situation is that there's usually still a smidgen of gas flow from the main burner, even though the main flame went out. Now...this is the important part: The proximity of the pilot burner may not be close enough to relight the gas at the main burner's ports in a low gas flow situation. Keep that in mind.
    So THEN...as the oven temperature drops and the thermostat begins to slowly throttle in more gas, if that gas still hasn't found the pilot flame YET, the gas will more or less build up inside of the burner chamber. When the right air currents and fuel/air mixture finally presents itself to the pilot flame, that gas will light off with a big ole POOF!
    In this little episode, the pilot might get blown out.

    That's why Badbozo was asking if that FDO thermostat had been replaced recently. They are replaced W-A-Y too often by DIYers or techs that don't know how to set them up properly.

    * * * * *

    On that note, there is one more thing I recommend you should do.

    With the pilot burner off, give it a solid couple of blasts with nitrogen. To be even more thorough, remove it, disconnect its gas supply tube and blast it through the inlet.

    We all know that air-to-fuel ratio is roughly 10:1. The pilot burner orifice diameter is roughly the same as a...uh...hair. ANY debris that the air carried in to sustain the ever-present pilot flame can eventually build up around the the top of the pilot orifice hole and affect its gas flow. So, as a rule, whenever you're having pilot issues, give the pilot a good blast of nitrogen to blow away that debris.

    I'll add that I've gone so far as to flush out those things with coil cleaner or alcohol. There's lotsa grease in kitchens, so a little degreasing might also help a pilot breath better.

    Just a suggestion.

  10. #9
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    tanks guys for all the input will try all of these options and hopefully i could figure this thing out thanks

  11. #10
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    I had a Fryer one time I was working on that would drop the pilot every time I cut the thermostat on. I ended up replacing the gas valve to fix the issue.

    Also this is my first post here. Hello everyone

  12. #11
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    Be sure to check gas pressure on the problem oven while other ovens are calling for heat.

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  14. #12
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    I would replace the ignition control board. Most of my pilot issues are always the ignition board. It could be a sign that it's getting week. We use or ovens daily as we our a school.

  15. #13
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    Six year old thread, folks.

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