Case of the boiler that failed on low water

Even though the customer blew down his boiler several times a heating season, the boiler still dry fired. Every time he blew down the boiler, the burner would stop, confirming the low water cutoff worked. Dry firing means it kept firing even though there was no water in the boiler. The cause of the accident surprised me. This was the first time I learned about the Evaporation Test for steam boilers,

[@freethinkerofny9187]

Thank you for conveying the information on the evaporation test. I completely rebuilt my wet line, main header and boiler last year. Since then I have been checking my McDonnell and Miller 67 by doing the blowdown test but I will now do the evaporation also.

[@boilerroomdetective]

Thank you very much I appreciate it Have a great weekend

[@Joop5000]

Ray, Those float type low water cut offs get nasty for sure! The probe type low water cut offs are a head ache too, the probes get dirty and malfunction. Not too long ago I commented on one of your videos where a friend / customer had his float completely fall off and just lay in the housing. But fortunately for him, before it fell off it actually did it's job and shut the boiler down. That's what prompted the service call, it would not fire back up, good thing! Anyway I took it all apart and scraped out all the junk. I should mention that this customer regularly flushes the low water cut off, regularly meaning every couple of weeks, but it still happened. I know for sure he regularly flushes it because he has his elderly Mom there and he wants to be sure to minimize any no heat calls. I stressed the importance of keeping that unit as clean as he could, I told him that he can never flush it out too often, the more often the better.

[@boilerroomdetective]

The float low water cutoffs, especially the #67, are a pain to clean but worth it. I never had one where the float fell off. I believe they are adding more chemicals to the water now. We are seeing more leaking nipples or it could be the piping is thinner. Thanks my friend