Pilot flame too intense

[oparr]

It's wasting gas and killing thermocouples. Finally decided to research this after another thermocouple died today after only two or three seasons. The boiler's manual shows a pilot flame profile but unfortunately I'm unable to view the actual flame from the side so I've adjusted the flame so that the thermocouple shows no signs of glowing red but is obviously hot enough to maintain pilot gas flow. Does this make sense? Thermocouple is centered properly and flame is hitting it in the right place. I could tell based on where started to glow first when lighting the pilot before it was adjusted.

[Tony Hwang]

Hi, Some gas valves have a screw for adjusting pilot flame size.

[oparr]

I know, already adjusted flame.

[Meat Plow]

If it's hot enough to maintain the pilot that should be fine. I've actually adjusted pilots using an adapter inline with the thermocouple that gave me a test point to monitor the voltage the thermocouple produced. There is a point where adding more flame makes no change in the voltage and that's usually with a very minimal flame, just enough to surround the thermocouple.

[oparr]

Unfortunately, what's happening now is that the pilot is fine until the main burner kicks in then it dies. I'll increase the flow until all is well on both fronts. Trial and error I guess.

[Meat Plow]

Make sure your flue is clear and that the burner(s) light without delay. You might be getting a puff while they light that puts a smaller pilot flame out.

[oparr]

Oh yeah, the main burners light as soon as the solenoid sounds, that was always the case. Seems like the pilot would go out after the main burners turned off and not when it kicked in as I had originally thought. Anyway, it's working fine now after further adjustment. I adjusted the pilot gas flow so that it took the specified one minute to stay on when lit from cold. Thermocouple glows red now, however, the flame is about half as intense as before. Going to replace the pilot burner assembly as well, orifice may be degraded, it's 28 years old.

[Meat Plow]

Ooooooo 28 years old, you didn't mention that. I don't think it's abnormal for the tip of a pilot to glow a bit. I guess I misunderstood you as to when the pilot extinguished. When there is a situation where there is an adjustable pilot, my training was to meter the thermocouple voltage output in circuit. The adapters I used to do that also served useful in saving time when there was a problem with the pilot. Took a minute to hook the adapter up and measure millivolts versus 5 or more minutes to replace a thermocouple only to realize that wasn't the problem.