Utica Boiler MGB150HD Shutting off after a few minutes

Hello everyone,

I am working on diagnosing my boiler system now since I noticed it went out today. I first attempted to just relight the pilot light and that seemed to get it to kick back on but yet again it shut off after a few minutes. I am still fairly new to the system so I started to read and poke around and noticed the following about my system. It roughly has the following flow.

  • The water supply is teed from the cold water from the water heater so it should be automatic.
  • I have a regulator valve to keep the system at 12psi
  • I have a backflow valve
  • I have the resevoir
  • I have a White Rodgers device that is set to 25? maybe this is an air regulator
  • I have a safeguard low cut off valve
  • The system then going into the boiler and comes back out and is split into three zones

One concerning part is the pressure and temperature gauge has water in the gauge. The temperature still responds but the pressure doesn’t move at all so I am not sure what the pressure is. The zone valves are still working turning on and off and the pipe gets hot so the heating works when the system is on. The burner flames are very yellow compared to the blue I would expect and I am thinking that this maybe one of the suspects.

Other things I have done: Took out the thermcouple and sanded it off. I hooked my meter up to it and held a flame to it and it slowly changed but then it eventually went negative (not linear responsive like I would suspect). Took some water out of each zone through the valves to try and bleed any air out.

So that smattering of information is where I am currently at. At this point I could swap out the thermcouple pretty easily to try and eliminate that but I still really need to swap out the gauge for the pressure and temperature to get a better idea of performance.

So what do we think we’re looking at? It runs for 5 minutes and then….high temp limit (thermocouple), low water/pressure limit (system issue), other?

Thanks in advance,



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