Steam boiler troubleshooting
Good Morning ,
Any plumbers out there.
I have a 40 yr old 200,000 BTU steam boiller residential
Working fine for last 30 years . Was turn off for nearly 18 months and recently relite.
Problem – i can light the pilot – it stays lite – i turn on the switch and the boiler fires – it gets hot- the pressure builds to 2 lbs it runs for several hours and goes off including the pilot .
just now i lite boiler and it would not fire and i did not hear the usual clicking sound from the gas valve of pressure trol
Just because your a plumber doen't mean your a boilerman, let alone steam.
Post your question over on Heatinghelp.com and thier forum, "the wall".
Very friendly and smart folks. They have a section just for steam heat.
I'm not a plumber or boileman. I just have several years experience with old commercial heating boilers., So I'll take a SWAG.
The intermitent pilot failure sounds like a thermocouple going bad if it is and open fire chamber boiler. If it is a sealed chamber it will have a flame sensor, either IR or UV, that is dirty or gone bad. The flame sensor tells the control valve unit that there is a pilot lite and allows the valve to open and the main burner to ignite. Other considerations are pressure switches and other safeties if the unit is a forced draft or fire tube system
Since the unit is 40 years old, you likely don't have a wiring schematic on it, but it would help if you could give more information about the unit. A lot of information can be found on the internet with just a manufacturer name and model number.
Yeah, the failure mode you describe is most suggestive of a bad thermocouple. But before replacing it, you may want to just loosen and retighten the connection between the thermocouple and the gas valve and try that out -- it may be a little corroded.