I have a 7 year old laars lx400 low nox heater that is causing me soooo much trouble! I was hoping for some advice. The heater was working ok, but then started getting AGS errors and blowing the EXTSW1 fusible link sometimes. I noticed some blow back - so I took out the burners and cleaned and replaced ones that were burned through. A bunch were clogged up and nasty. I reassembled the heater and it lit and ran fine - no blow back - nice and quiet - blue flame - but after a few hours it burns out the EXTSW1 fusible link. I don't think it is blowing back - in fact, I used an IR thermometer and think it is just running really, really HOT! The fusible link is doing its job.
What could cause this? I know the burners are new and clean. Could there be soot or something on the heat exchanger? The vent stack and lid are really hard to get off, making getting to the heat exchanger really hard - so tell me that's not it, please. I did have to swap out the 3HP Northstar pump with a lower performing one - a 1.5HP pump - so the flow rate is lower than normal. This would lower the rate that the exchanger removes heat so it could cause it to overheat... but it shouldn't if the pressure is high enough to trip the heaters flow rate sensor, right?
I need to get a replacement pump that is sized right, but in the meantime, I would like to heat the pool! Any suggestions?
thanks so much!