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Message to Tim McElwain

Roy Tenn
Roy Tenn Member Posts: 15
in THE MAIN WALL
Hi Tim,

First off I would like to say I really enjoy your post and comments on all HVAC topics. Keep up the good work.
I have a question about thermocouples.I installed one last
Sept.( 6 mts ago) and now it failed. I had to replace it today. The pilot flame engulf it normally and everything seems ok. I noticed the defective thermocouple tip is burnt
severly. This is a Honeywell 36 inch standard thermocouple.The boiler is a Weil-Mclain. Problem is on going for 3 years now.
Your thoughts? suggestions?
Thanks in advance.

Roy

Comments

  • Unknown
    Unknown
    Tip burned is usually

    a case of the pilot flame being adjusted to sharp. Soften up the flame so that the tip glows "dull red" instead of "cherry red". The pilot should not be roaring but quiet. The flame should hit the upper 1/2 to 3/8 of the thermocouple.

    The other cause of failure is high temperatures in the combustion chamber and the pilot getting excessive temps for long periods of time in particular when it is very cold and the system is running for long periods of time. In attempting to get higher efficiencies from boilers and furnaces we are holding heat in longer and getting higher temps near the thermocouple. A good solution is a Johnson Controls nickel platted corrosion and high temperature resistant thermocouple the part # K16RA.

    I also like to do a combustion test when dealing with this problem to determine proper air mix in the chamber which helps to keep the area of the pilot at an acceptable temperature. It has been my experience that when I can get CO below 100PPM air free the pilot temp is reduced and runs much better.
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