I have a Max-E-Therm 200HD NG heater that has been having exhaust temp issues. The heater worked with no problems last year, but this year it will not run longer then 1-3 hours before hitting the exhaust temp limit and shutting down (SFS led light comes on). I checked the exhaust and nothing is restricting the flow, and the sensor checked out OK. When I display the exhaust temperatue on the heater by holding down the on button it shows the exhaust is at 460-470. I have a temp gun and measured the temp at roughly the same location as the SF sensor and it reads 300-350. Also when the burner shuts off the exhaust temp display on the heater will match the exhaust reading of the temp gun (300-350).
Has anyone seen this problem before?
Since the heater is still under warranty I had Pentair send some one out to look at the heater. They told me that the heat exchanger was sooted up and needed to be cleaned off. The guy that they sent out said he would gladly do this for $600 . So I ended taking the heater apart myself to get to the heat exchanger and there was no soot inside the heater. After this I called Pentair and they told me that the problem was that there was not enough gas pressure. After the heat exchanger issue I was skeptical of what they were telling me. So I asked if there was not enough gas pressure how could the heater get hot enoguh to over heat. They could not answer my question. The latest is they are sending a new control board for the heater after I called a bunch of times . However I still wanted to see if anyone else has had this problem in case it is not the control board.
Thanks for your help