Troubleshooting a CB Firetube Boiler

I have had the modulating dampers get out of sync in the past which has caused interlock failure. The best bet is to replace the damper motor once they get out of sync you can adjust it but they will slip again.

Or the linkage is binding on the prepurge causing the interlock drop outs.

What model is the flame safe guard system? ie; CB 780 , does it have an expanded annunciator CB783?

At what stage does it lockout? Does it lockout during the start up or while running normally? Does it get past the purge cycle? Have you check the Pre-ignition interlocks (fuel valve proof of closure) and flame signal check during Standby and Pre-Purge. If running have you checked flame scanner; aimed at flame correct, dirty lens, amp signal is adequate (measured with meter)? Is it giving a lockout code (if annunciated) .

As you can see more information is needed to determine the cause, simply replacing all of the components without finding the cause can be a waste of time and money.

I once worked on a new boiler at a hospital that would only lockout when the makeup air temperature in the boiler room dropped to low. The endless search to find the cause, believe it or not was the cold air. The makeup air heater was steam heated and once steam was lost it could not heat the air coming into the boiler room. The fuel/air mixture (O2 density changed) would change and the scanner could not see the flame and the boiler would lock out. We ended up using a magnification lens on a more expensive IR scanner. All systems check out repeatedly during the trouble shooting, replacing parts was futile.

I would suggest calling in the CB FSR.

Dear DMR, Try this ..........http://www.boilersupplies.com/warrick/ Your warrick lwco control is now been discontinued. Replace it and buy a spare too, then come back and give a GA to the right answer.