pilot keeps going out

jay_50

I've been working on a smith gb-100 boiler that the pilot keeps going out.I replaced the thermocouple twice and also the gas valve.The gas valve cured the problem for 24hrs then went out.The boiler is in a small room with less than adequate combustion air.I corrected that issue but I still have the problem and cranky customers.Any suggestions would be appreciated.Thank you.

captainco

Pilots constantly going out is a potential sign of a dangerous piece if equipment doing its job. It can often be a sign of flue gases spilling and displacing the air with CO2 which is heavier than air. Not sure if it is venting that you should have fixed instead of combustion air. That would require a combustion analyzer and a draft gauge.

delta T

So many possibilities, as Captainco said, could be a draft/combustion air issue, could be gas pressure issue. Is the pilot clean and adjusted to a proper flame? Have you watched the boiler fire under its normal operating conditions (door to room closed, cover on front of boiler, etc)? any cloths dryers or stove exhaust fans or the like that could cause a lazy start that is blowing out the pilot on ignition? Has the venting been inspected as far as is possible to insure that it is the right size, and within specs on any horizontal branches according the IMC?

In my experience an intermittent pilot failure is usually caused by something wrong when the boiler fires. If it can't light off properly and rolls out, or it creates too much draft initially (rare) the pilot can go out. You just have to start eliminating possibilities one at a time. Start with checking draft under normal operating conditions as stated above, make sure there are not fans or anything running, make sure it is in spec there. Then do it again with all bathroom fans, clothes dryers, stove hoods etc, running and check it again. Still good? move on to the gas pressure. Make sure your mainfold pressure matches the rating plate, check your orifice size and make sure it is correct, check your inlet pressure (static and running), watch the pressure for awhile while it is firing to make sure the gas company's regulator is not wandering. So on and so on, and eventually you find the problem.

Tim McElwain

Do you know how to take millivolt readings? Do you have a combustion analyzer?