Came out today for a no heat call. Upon inspection I found that the systems emergency switch at the top of the steps was turned off. I turned it back on and the system received the call for heat. I observed the system starting until it received an error code 15 for an open limit. I traced it back to the spill switch behind the system I reset the switch and the system tried to start but after 3 seconds it failed again. There was no time for the limit to be reached the limit reset button is faulty and will not reset. Installed a new limit switch and tested the system. I observed the system starting normally. I let the system run for about 20 minutes until it reached the temp limit. I took a combustion analysis test and received the following readings, o2 is at 8.9% and the co levels are 12ppm. The burners went out but the circulator pump continues to cycle until the water temperature goes down . The system is operating properly at this time. The systems model # is smeared. See photos.