Jandy Pool And Spa Heater Not Working

[sogden]

I have a jandy LT 250 NOX pool and spa heater. The heater was working fine, when one day i tired to heat the spa and the heater would start then would pop like a gas relief valve went off. Then the air flow LED would flash. I checked the hose and switch and could find nothing wrong. After several attempts to start the heater, the error led changed to Hi limit and the blower would not run at all. I purchased and new blower and installed that, but still no blower function and i cont to get hi limit error led. any ideas?

[Pool Clown]

Haven't worked on too many of those but from general experience, A Hi limit fault is sometimes caused by a improperly functioning Thermostatic or mechanical by-pass. Man, That blower musta been expensive... That popping you heard sounds like "banging". It's when the water begins to boil cuz the bypass is stuck open and flow thur the collector slows down to a point where the water 'Cooks". Once the water reaches a predetermined temp, the hi-limit opens the safety circuit, and the heaters gas valve closes. Once that happens, the water begins to cool, closing the high-limit signaling the control for a call for heat and the whole circus begins again.

Take the by-pass out and look for cracks in the bulb looking part of the thermostat.

Good luck