Vulcan 36L Oven control?
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  1. #1
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    Vulcan 36L Oven control?

    I have a Vulcan 6 burner stove with oven and I'm having trouble with a low flame in the oven and it takes forever obviously to bake anything. This is NOT a convection oven. I'm making the assumption the oven thermostat is to blame since the safety valve is just open and closed. The stove burners are fine. Is there someway to test the oven thermostat? Looks like gas comes from the manifold, thru the oven thermostat, then thru the safety, then out the burner.


    BTW, the part I'm looking at for replacement is 417424-G1


    Thanks for any info.
    Last edited by tcape; 05-01-2013 at 04:31 PM. Reason: added more information
    "Delay is preferable to error"- Thomas Jefferson

  2. #2
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    i would first check gas pressure, then verify orifice is clean. t-stat just turns burners off and on at a set point it doesn't control flame height. test with a t-couple and thermometer at 350 degrees.

  3. #3
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    question

    Quote Originally Posted by kklobas View Post
    i would first check gas pressure, then verify orifice is clean. t-stat just turns burners off and on at a set point it doesn't control flame height. test with a t-couple and thermometer at 350 degrees.

    The oven was working fine a few months ago and all the top six burners burn fine. I did take a short video of it, but I don't have time to post it right now.. maybe in the AM. But the flames barely make it out of the burner tube slots, and that is when all the stove burners are off.

    I understand the thermostat and the safety are just on and off... and it does seem like a pressure issue, but the stove burners and the oven burner are both after the regulator and the stove burners burn fine. I will recheck anyway.


    Thanks for the reply
    "Delay is preferable to error"- Thomas Jefferson

  4. #4
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    I would remove and clean burner and orifice too. Could be restricted

  5. #5
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    Your thermostat looks like this:

    Name:  BJ tstat.jpg
Views: 599
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    This is a BJ series throttle-action thermostat. The BJ thermostat is really the best of gas control thermostats - due to its accuracy.

    It operates as it's name implies. When adjusted to a desired temperature, it provides full flame. As temperature nears setpoint, it throttles back the flame until the thermostat is satisfied. However, when satisfied, it should NOT shut the gas flow off completely. It should still have about a 1/8" flame from the burner. That flame is called the bypass flame.

    The bypass flame is set up during the thermostat's installation in the factory or by a technician installing it. As shown in the picture, there's a straight-slot gas flow adjustment located on the thermostat body which adjusts gas flow for the bypass flame. There will be a raised "B" next to that adjustment in the thermostat body's casting. There's another adjuster is for pilot flame adjustment, used in applications where a pilot burner feeds through this thermostat. More often than not though, I 've found the pilot port plugged off or nonexistent.

    If the bypass flame is set too low, it will flutter around the burner and possibly go out. If the bypass flame goes out and the thermostat throttles for more flame (for more heat), there's often some gas buildup before that gas finds the pilot flame. There's generally a very notable reignition in such a situation, much like setting a small puddle of gasoline in your driveway on fire. Sometimes the reignition will make the pilot go out due to an inrush of air.

    If the bypass flame is set too high, it will cause a rise in oven (or griddle) temperature despite the thermostat's setpoint. Remember - this thermostat throttles back to it's smallest flame when satisfied...the bypass flame.

    If the bypass flame is set correctly to 1/8", the flame will be steady and uniform around the burner and helps keep oven temperature at or near setpoint during low food production periods.

    With ALL of this said, I think you have a bad thermostat. If the burner flame never goes beyond what you described, which sounds like just the bypass flame - and even when the oven is stone cold and you set it for 500 degrees -then the thermostat is bad.

  6. #6
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    Here is a short video of the burner, and I have it turned up to 500. The oven was not running at all prior to me arriving so the only heat in the oven was from the pilot light.
    "Delay is preferable to error"- Thomas Jefferson

  7. #7
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    That video shows a properly adjusted bypass flame. The thermostat is not calling for heat. Replace it.

    When you install the new one, make sure you check and adjust adjust the bypass flame to the same flame level as in your video.

    What I do with a new thermostat like that which I've just installed is set it to a moderate heat such as 300*.
    Let it preheat. Monitor the temp with an accurate digital thermometer. Of course, when it gets around that temp, the thermostat should throttle back. You may find that some minor temperature calibration is in order. Not yet though...

    With the oven temp at or near that setpoint, turn the stat back down 50 or so degrees. Inspect the flame, which is the bypass flame. Adjust the bypass flame by turning the adjusted screw in (CW) to decrease flame height...or out (CCW) to increase flame height. It is critical to have it properly adjusted. Once you're satisfied with it, you won't need to do it again. It's set up.

    Go back to checking/adjusting calibration. A general rule is to allow a thermostat to cycle twice before adjusting calibration. That's difficult to observe on this style stat. So...just let it heat for about 20 minutes - empty and with the door closed.

    The oven temp should have settled by then. If setpoint and your digital thermometer are different by more than 10*, the stat needs some calibration.

    To adjust calibration, remove the stat knob and POP out the round center cover. While the knob is off, note the calibration adjustment screw recessed inside the tstat stem. Then reinstall the knob.

    Insert a narrow-bladed straight slot screwdriver through the knob and engage that calibration screw. Push IN on the screwdriver but DO NOT TURN THE CALIBRATION SCREW. You'll note some springiness to it. When you push in on the screw, it no longer meshes with the knob hub, so the knob will turn independently of the internal works that sets the temp.

    So, with the calibration screw pushed in and held steady so it won't turn, look at your digital thermometer to note actual temperature, then turn the oven knob to match it as closely as possible. Then remove the screwdriver, letting the calibration adjuster seat again. The oven should be accurate now.

    Don't forget to put that round center cover back into the knob.

  8. #8
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    I failed to mention that I typically calibrate an oven at a setpoint of 350*, since that's the most commonly used setting.

  9. #9
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    Quote Originally Posted by ECtofix View Post
    I failed to mention that I typically calibrate an oven at a setpoint of 350*, since that's the most commonly used setting.
    Thanks so much for the information, it was extremely educational. I knew the basics about these kinds of controls, but your info has added to my knowledge!


    Thanks again,

    Tony
    "Delay is preferable to error"- Thomas Jefferson

  10. #10
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    Glad to help out. When I was doing service work in the field, I often encountered these particular thermostats that weren't set up correctly when they were installed.

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