I have a Sta-Rite SR333NA at a pool I've recently taken over from my in-laws. The heater has worked inconsistently for years. Looking into the error code, it's the SFS (Stack Flue Sensor) that's at fault. I found a very helpful set of videos on YouTube (Part I: ; Part II: ) detailing the work that I've now gotten into.
My situation does seem to be very much in line with the video's situation (high exhaust temps, shutting off after a few minutes, service heater light on, and now that I've dug into it, buildup and liming on the coils). You can see the liming evidenced after a pressure wash in the picture of the heating coils below. I now have two issues that I'm trying to resolve:
1. Have I done enough with the pressure washing to delime the coils? I'm tempted to use CLR (or something else on a recommendation) to further get at that buildup before I close it back up and put it in service. Any experience and/or recommendations?
2. Mice have clearly cozied up in the insulation that was under the stainless steel bowl that the coils sit in. There's also plenty of char, lime and perhaps a little more chewed up bits taken out of the insulation (see the other picture). I assume I should be replacing this insulation, and am wondering if I need to get the OEM kit or if a hardware store would sell sufficient material that I could cut to fit? I have enough of each piece that I could attempt to match them, but was wondering if anyone has gone this route?