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thermocouple failure

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hope it helps.

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  • jack de witt
    jack de witt Member Posts: 1
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    thermocouple failure

    i keep having thermocouple failure, i've replaced 3 in the current heating season. i've tried various positions in the pilot flame with no success, i have a slant fin gg-125 galaxy boiler,any suggestions? thank you. crankcase@att.net
  • Joh n Brickey
    Joh n Brickey Member Posts: 43
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    I'm not sure why they would be going out so fast,but you might consider putting an electronic ignition system on your boiler.
  • Mark A. Custis
    Mark A. Custis Member Posts: 247
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    John might

    have something there. Are you sure the t-couples were not bad out of the box? UEI makes a business card sized multimeter that reads DVC into the micro amp flame rectification range. They run about $35. In the old days when I knew everything I assumed all new parts wre good. Not any longer.

    I have taken to testing all sorts of sensors and parts, I quick clip with the aligators, light the piolet while holding down the electromagnet plunger speaks volumes.

    All of that blutted out you could just have had bad luck.

    They should read about 29mvdc new, Bill can correct me, but if I see 18 to 19 mvdc on one of his valve products I leave the thermocouple in service if the outer jacket has not started to burn through.

    The meter is about 1/4 the cost of a spark ignition converstion kit and with it you will know what is going on. Thirtyfive bucks is not much to know you are correct in changing the ignition/flame proof system.

    Warm regards,

    Mark

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  • Glen
    Glen Member Posts: 855
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    bad to the bone -

    and right out of the box too! It's more common now than in the past. QC ain't what it used to be. Out of a recent of box of 24 inch thermocouples - I threw away three of them. Test everything - is very good advice. That said - not all tc's are created equal - and some gas valves require a slightly higher voltage - like the JC Husky model. Just a thought ----
  • Mark A. Custis
    Mark A. Custis Member Posts: 247
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    Glen:

    I promise that I will work harder at my rightins when I give advise. I will at least attempt to add more of what I think I know.

    My mind was thinking of MGVs less than 350K.

    I proudly stand corrected.

    Thanks,

    Mark

    To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
  • Thermocouples

    1. Pilot should envelope upper 1/2 to 3/8 of the thermocouple.

    2. Adjust the pilot so that the tip of the t'couple glows "dull red" not "cherry red" if it is too sharp it will weld the tip.

    3. The pilot flame should be adjusted to give a soft blue flame. Not noisy or roaring. The adjustment is made at the pilot adjustment screw on the gas valve, screwing down decreases flow screwing up increases flow. Remember pilot gas is on line pressure it is not regulated.

    4. When diagnosing thermocouple problems you need a "millivolt" capable meter. One with DC volts will typically give you a read out. The Open circuit reading should be between 25 to 35 millivolts depending on the style of t'couple and the pilot. Minimum reading on t'couple 17 to 18 MV's if less than that clean the pilot or replace t'couple.

    5. The closed circuit reading should be roughly 1/2 of the open circuit 13 to 17 mv's you need an adapter to be able to take this reading either a Johnson Controls Junction Block Adapter part # Y99AN-1 or Robertshaw part # 10-038 Thermocople Test Adapter.

    6. Next with the meter connected bring the burner on and let it run for 15 minutes. Observe the meter readings they should fluctuate very little. At this time all the doors should be in place simulating actual conditions. Does the flame charcteristic change at all or do the readings change.
    If they do you may have a combustion problem or venting problem. This is also a good time to take a combustion test on the equipment CO2, O2, Stack Temp, draft, CO etc.

    7. It should also be noted that in extreme periods of cold weather with long cycles on boilers extremly high temperatures can be experienced in the area of the pilot. My experience with this has been that it is not selective to any particular boiler. It usually occurs with the pressed metal burners versus cast iron. It is also typical with vent dampers which close when the call for heat ends and keeps temperatures much higher for longer periods of time in the combustion chamber.

    8. What I have done in those cases is to use a Johnson Controls High temperature nickel plated thermocouple. The part number is K16RA. This t'couple can with stand much higher temperatures than normally experienced. I often used them on Pizza Ovens.

    I have a complete procedure for sale with illustrations to assit in being able to trouble shoot and diagnose these problems. E-mail me if you are interested.
  • Ben_3
    Ben_3 Member Posts: 71
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    Thermocouples

    Ah the Husky a true heating mans t-couple that puppy will never go bad only one I use If I can get it in the pilot. As for mv readings I used to have a Baso meter that I used to test them and most good t-couples under load{ keepimg pilot valve open should read about 18mvdc. Most all gvs only need a constant 7mvdc to hold open. It has been my experience that its all about postion and heat. If the t-couple isn't postioned in the pilot just right you can burn them out Should top covered in flame apporx. 3/8" and not to deep into the flame that it's splitting th flame. Don't get me wromg the top needs to be covered by the flame and not to far away where it only touches the side. Next is you pilot when on unusually loud? many gvs have a pilot adjustment and can make all the diff. in the life of those poor t-couples
  • Mark A. Custis
    Mark A. Custis Member Posts: 247
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    Timmie:

    Do you remember all this data?

    Your wealth of knowledge contiues to save my person from bodily harm.

    Mark

    To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
  • [Deleted User]
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    Give me a call at Slant/Fin

    I'd like to try to help.

    800 873 4346 ext 456

    or

    516 484 2610 ext 456

    Noel
  • Thermocouples

    check out.
  • Big Ed
    Big Ed Member Posts: 1,117
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    Timmie

    I read a few posts about chemicals stored in the area of the boiler causes thermocoulping failure. Is this true ?
  • For Scott Milne

    on thermocouple problems.
  • frank_10
    frank_10 Member Posts: 2
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    thermocouple

    install a new gas valve, guaranteed success/ ran into this problem many of times, was puzzled just like yourself, starting changing gas valves if problem persisted, never got called back again
  • frank_10
    frank_10 Member Posts: 2
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    thermocouple

    install a new gas valve, guaranteed success/ ran into this problem many of times, was puzzled just like yourself, starting changing gas valves if problem persisted, never got called back again
  • Eric Tardif
    Eric Tardif Member Posts: 38
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    Loud Pilot Flame

    I just had my oil steam boiler replaced with a one year old Burnham V83 converted to steam and gas. The total job (equipment, parts, labor, etc.) cost $3200. The power gas gun pilot light is very loud. I can hear it 10 feet away. The heating-man/plumber said that it was preset by the factory and he wasn't going to touch it. According to Tim's instructions, it should be adjusted, right?

    The oil to gas converter gun is a Wayne P265. In the mean time I'll check the manual.
  • That Wayne burner

    needs to be adjusted by a professional gas combustion/conversion burner expert. I would get that done as quickly as possible.
  • Eric Tardif
    Eric Tardif Member Posts: 38
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    Any in Boston?

    Do you know anyone in the Boston area? I'll do an internet search.
  • Eric Tardif
    Eric Tardif Member Posts: 38
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    Called a Pro

    Thanks for the info Tim!
  • Fitty
    Fitty Member Posts: 6
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    zunkels

    Ben,
    My name is Tom Zunkel. My folks came from Emmetsburg, Iowa, supposedly emigrating here from Germany in the 1890,s. supposedly there were 4 brothers that jumped ship in New York. 3 brothers went on to Iowa, one stayed in Ohio. I am mildly interested in another branch of that family.
    Please let me know if your family story tallys with the above.
    Incidentally, I am 70, a retired tech writer and illustrator, happily divorced. I have a brother, ****, who just retired, and was chief engineer and consultant in the door hardware business.
  • JoeV_2
    JoeV_2 Member Posts: 43
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    Thermocouples or flame rods?

    I am confused and have to ask if the correct terminology is being used here...

    Thermocouples have two wires to measure temperature. Flamerods have a single wire to deliver positive voltage and uses the pilot flame as a resistor to complete the circuit to ground.

    Do I have it right?





  • joev you have it wrong

    may I suggest you get some basic training.

    Thermocouple as we use it in gas heating is two dissimilar metals welded together so that when heat is applied to the tip (called the hot junction) the difference in temperature between the hot and cold junction causes a small millivoltage to be created which is sufficient to energize an electromagnet which holds open a safety valve seat by magnetism as long as the pilot is lit and burning blue, soft and enveloping the upper 1/2 to 3/8 of the tip. The tip should glow dull red not cherry red as that will weld the tip and damage the thermocouple. Technically the thermocouple is two wires one is the inner copel lead the other is the copper outer casing of the thermocouple.

    Flame rods use flame rectification which is created by superimposing a AC signal electronically on a circuit and allowing that AC signal to pass through the flame of the pilot. Then by creating a greater ratio to ground area versus rod area (4 to 1 is the minimum) a small DC microamp signal is created, usually 2 to 10 microamps. This is accomplished by using the flame ionization process of the ionized particles in the flame. The ability of a soft, clean blue flame to conduct electricity makes it happen.

    Hope this helps.

    I have all kinds of written material on all of this which is quite helpful in understanding these concepts.
  • JoeV_2
    JoeV_2 Member Posts: 43
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    Thanks Tim, I am not a heating man.

    I understood the principle of operation of both devices. I didn't realize thermocouples were used in home heating systems. I have worked on industrial oil/gas combustion systems that have used either flame rods or UV sensors.

    On my old boiler, I converted a standing pilot to electronic ignition and it used a flame rod. Actually, on my existing hot air furnace, I have a flame rod as well.

    I have worked with thermocouples in a lot of applications, never in a flame safety circuit. That's why I was confused.
  • Joev, Glad to be

    of some help.
  • Bill W@Honeywell
    Bill W@Honeywell Member Posts: 164
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    Pool or laundry chemicals...

    primarily chlorine are the usual suspects. Detergent powder also. Lint from clothes dryers can also be an issue for the whole burner assembly, not just the t'couple. White or green discoloration can be indicative of either form of contamination.
This discussion has been closed.