Eating Thermocouples

don_52

Gents,

Johnson (BASO)

K16RA NICKEL PLATED HI-TEMP T-COUPLE

K16RA-24C
K16RA-36C
K16RA-48C
K16RA-60C

The -dash_ # is length, not sure about 18".

HTH, db

reevesjo_2

Eating thermocouples

I have a 12 year old Haugh's G400 natural gas heater that eats thermocouples. I think Haugh's was bought out by Jacuzzi, but I can not find out for sure. It has a 3/8NPT SIT 630 Eurosit #630516 gas valve (Italy). The valve is not electric. I have replaced the thermocouple three times in the last three months, with a Honeywell Universal 30 millivolt. The last time with a LUX standard copper 18" CC0018 because the Honeywell was not available.
Question: What am I doing wrong? It works fine for awhile and then just fails. The pilot goes out and will not start again without replacing the thermocouple.

Mark Eatherton

Pilot flame too hot???

I know the old saying of "They don't make'em like they used to" definately applies to thermocouplers. Was a time that you NEVER had to replace them. Now a days, everyone in the company has half a dozen at any given time. We have found that the Johnson Controls Bull Dog (?) extra heavy duty coupler seems to hold up well.

It was pointed out to me by someone I trust dearly (Timmy Mac) that if the pilot flame is too "hard" that it can cause early thermocoupler failure. Try backing the flame down a bit. It doesn't have to look like the neutral burn of an oxy-acetylene rig...

I'l check the brand name on the Johnson coupler. Bull Dog doesn't ring true for some reason.

ME

Boilerpro_5

Yep, what Mark said.....

Adjust the thermocouple so after it is in the flame for several minutes the thermocouple is only a dull, not bright red. Also the flame should only envelop the top 3/8 to 1/2 inch. Get an electric meter. Output should be 24 to 30 MV for most systems. Also look for leaks where the pilot tubing enters the pilot, if a flame is burning here it will eat the thermocouple.

Boilerpro

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lchmb

test

Have you tested to see at what point the gas valve is dropping out? Is it possible it's not the thermocouple but in fact the gas valve?

reevesjo_2

Thanks for all the good, quick advice. The thermocouple did appear too red, so I backed the pressure down on the pilot. Now, the thermocouple is "not quite red" and the pilot is staying lit and the burner fires up OK when the thermostat calls. So, I will leave it here for awhile to see what happens.
Joe