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burned out thermocouples

We have been using JC husky thermoucouples #k16bt-36 for 20 years or so, they use to be penn baso. better output than the honeywells (sorry Honeywell) and better lifespan. Little more money but definately worth it.


  • ScottMP
    ScottMP Member Posts: 5,884
    Last night

    Went on a service call and replaced a thermocouple for a new customer. As I placed the old thermocouple next the other two that were on the top of the boiler, I wondered what would kill them off this fast.

    I have been reding the lower post about the better quality TH. But what would kill this off.

    Open basement, no paints,thinner or solvents near by, Atmospheric burner.

    End of the thermocouple looks like it was pealing. Very black, the others looked that way also.

    The pilot flamed seemed very large and lazy to me. I tryed to adjust it down but it seemed to make NO difference to the flame. I believe I had the right adjust location, ( small screw under a cap next to the pilot tube ).

    Any Help ?


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  • Gary Fereday
    Gary Fereday Member Posts: 427

    Scott, That may have been the regulator for the main burner. The pilot adjustment screw my well have not been located. You sould have been able to have shut off the pilot with the adjustment. Regulated Gas adjustment is for only the main burner. The pilot gas is not regulated ,but incomeing line pressure. anyway bigugh
  • Thermocouples

    I think you had the right screw. It will almost bottom out before you see a change. If this is a Honeywell VR8200 or 8300 valve spray some WD 40 into the hole after you remove the cap, let it sit a minute and then continue to screw down.

    Is the tip of the t'couple cherry red or dull red? It should be dull red. It sounds to me like the tip is being welded by too sharp a pilot.

    How often are thermocouples being changed?

    Also I suggest using a nickel plated Johnson K16RA t'couple they are like the energizer bunny they out last everything else. I always used them on Pizza ovens when I had restaurant service business.
  • Joe Kuhl
    Joe Kuhl Member Posts: 17

    I can't believe someone is actually suggesting you spray WD 40 into a gas valve.Do you have any idea what so ever whats under that cap? Why don't you mention that to your Honeywell supplier.See what they say.
  • It is not going into the gas valve it is

    to free up the pilot adjustment screw. Honeywell has not seemed to be able to solve this problem for over 20 years. When I was working as an instructor with Honeywell on their Source Program 1994 to 1999 I brought this to thier attention. The problem is still not solved. Not to pick on Honeywell this is a problem with all gas valves. It is caused by the gas itself, it builds up a white substance around the bottom threads of the adjustment screw. I have torn apart hundreds of gas valves and found this substance on most of them. I have been doing this (spraying WD - 40 into the threads) for 40 years on gas valves works like a charm and never did anything but keep you from having to put in a new gas valve because you can not adjust the pilot gas flow. If you are a Honeywell rep perhaps you can bring this to their attention once again. A fellow from Honeywell called the Control Pro Bill Ribble (retired) thought it was a great idea.

    If I could ask you what would you do to adjust the pilot to get it to keep from burning out thermocouples?
  • t-couple problem

    My 2 cents, if the tip of the t-couple is black and the pilot lazy, my guess would be a pilot orifice has been reamed out and causing the lazy pilot. get another orifice and see how it does.
  • Bob C.
    Bob C. Member Posts: 20

    A little late but I was wondering what type of boiler was it? (if it was a boiler) I had a problem with H-B smith boilers. I installed one of the boilers on a slab. The next week I installed the same (type, size) boiler for another customer BUT there was one thing different! this boiler came with a piece of paper taped to the jacket of the boiler that said it had to be installed on cinder blocks and gave a special arrangement. Well I thought nothing of it and put it up on the cinder blocks and did the same every other one I installed after reading the paper. I had to got back after one year and replace the tcouple on the boiler sitting on the slab. The white metal threads were distorted. I changed it Adjusted it and left. The following year I'm back again changing the tcouple. I had called Smith the first year and got a run around (check this, check that). I asked if it had anything to do with it sitting on the slab and I informed Smith that this particular boiler did not come with instructions to put on cinder blocks (yes I do actually read instructions). Anyways they finally give me this heavy-duty tcouple and now I only have to change it every two years(ha ha ). I wasn't laughin; eventually I disconnected the boiler and put it up on blocks. NOW ITS FINE! There was too much heat transfer to the floor. The blocks allow air to circulate between them removing the heat.

    Long winded BOB CAT
  • J Christensen
    J Christensen Member Posts: 2
    Burned out thermocouple

    What type of gas are you burning ? If it's propane try using a husky thermocouple. ( Johnson Controls )
  • now thats food for thought

    i'll have to remember that. may come in handy.
  • ScottMP
    ScottMP Member Posts: 5,884
    Natural Gas

    The boiler is a Utica. I believe it has a sheet metal base to it, so the makeup air and temperature around the burners is set.

    I have got one of my suppliers looking into the Johnson thermocouple. We may make these our standard replacment units.

    Good point about the orifice size, we'll check that when we service this new customer.


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  • Boilerpro
    Boilerpro Member Posts: 410
    The Husky's are available through Johnstone supply

    Even though the shorter sizes don't look as Husky as they used to be, they still have a Husky and long tip.

  • For high Failure on T'couples

    use Johnson Controls K16RA nickel plated thermocouple. It will withstand high temps that a lot of modern boilers develop around the pilot due to tightening up the sections on boilers in order to increase efficiency. What happens is when it gets real cold outside and the boiler is running longer the temperature goes up above the ambinet temp that t'couples are designed for.

    I have discovered this on a number of boilers. One way to overcome is at time of installation get the boiler about 3 to 6 inches off the floor.

    The tests I have run on this show a decrease in temperature as much as 600 to 1000 degrees lower temp at the pilot.
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