Unraveling Intermittent Boiler Flame Failures: The Ultimate Troubleshooting Guide for Technicians

We had a "job from hell", Latrobe High School, where we had so many flame failures that you could not fix that my boss had me stay all day so I could witness the burner failing. I spent about 12 hours there with meters on every device so I could find the culprit. The burner never failed until I left for the day. The head custodian called the shop to report that it failed as I was leaving the school.

My first 13 years in the business I did nothing but burners. Flame failure probably caused my anxiety issues LOL.

A few examples: (you never forget these once you had them)

Power Flame burner in a Town hall Honeywell R4140 control with lead sulphide scanner. Locked out every day. Every time maintenance reset it it started. This went on for months. I went to the job after work and pulled up a chair. The burner ran long cycles. Finally I saw it. It had to run a long time on a cold day to really get the combustion chamber hot. The scanner was picking up hot refractory on pre purge and giving a false flame signal locking out the control. Changing to a UV scanner fixed it.

Another Power Flame locking out. Around 1980 the programmers changed from a Fireye 5022 mechanical realy to a D-5022 solid state programmer. The older controls if a limit opened (like a bouncing water level) the control would simply shut the burner down and recycle. With the newer controls you would get a lockout. This job had been locking out for months. Pulled up a chair again. This building had a T87 stat pulling in a RA89a relay to start the burner. The burner ran fine till 9:00 am when the workers came in (office building). All at once the relay started to chatter. The thermostat was mounted on the wall next to the rest room doors. heavy door with a bad closer. Every time the dor slammed shut it rattled the mercury in the stat chattering the relay and locking out the burner. It only did this with the room up to temp wher the mercury was close to tipping.

We had 3 burners we serviced in Pittsfield, Ma. 2 hour drive. 2 were new burners and one was existing. All on 3 different jobs. All had been running ok and the cold weather hit and they all started locking out. We eventually basically tore all three burners apart looking for issues and found nothing. One was an oil burner and two were gas/oil and the gas oil was locking out on either fuel. All had gas pilots.

I decided it had to be a pilot issue.

I replace all the standard ignition transformers (6000) volt secondary with new ones rated 8500 volts. 120v to all burners was fine.

Fixed all three jobs. Talking with Berkshire Gas they wer "Gas shaving" adding propane to the natural gas to keep the pressure up in cold weather. Propane is more dense and harder to light.

I swear the burner knows as soon as you get in the parking lot and start your truck they go on lockout