Just put a new honeywell L8124C Aquastat Relay on my Weil-McLain
hot water boiler. I replaced the Relay because my burner clicks on Ignites for 30-90Sec and then pops off. The house is warm and I have 3 zones. I STILL have this problem (ie Burner Turns Off after short run time) HELP!!!
Could be overpressure switch, underpressure switch, overtemp switch, or, if a closed combustion, a leak in the either the air intake or exhaust or the fan that brings in the outside air may not be pressurizing the system properly. Well, it could be the flame detector, too. In other words, it could be a lot of things, and I probably haven't listed them all. You need to check to see if the control panel has any indicator lights, and review the manual for troubleshooting. A modern boiler has all sorts of safety switches and a sequencer...if something is out of wack, it shuts itself down. It is most likely a sensor switch, but could be lots of things including a real physical problem that the sensor is correctly reporting. If a bad switch, once identified, it may be simple to replace. But, don't just go buying new parts, as all of them can be checked prior to that if you have the proper tools and enough understanding and skill.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013