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Thread: Sta-Rite Max-E-Therm SFS Deliming

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    Sta-Rite Max-E-Therm SFS Deliming

    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?

    Thanks all,
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    Jul 2011

    Re: Sta-Rite Max-E-Therm SFS Deliming

    The heater is done for. I wouldn't put a penny or a dime into it. Was there water inside the heat exchanger chamber? From the looks of it I would have to say there probably was. If not, the discoloration was due to poor water flow thus causing the unit to sweat.

    You would end up spending a lot more money on that old unit than you should if you fix it. Save your money and buy something else. This units are garbage.
    Paul A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Re: Sta-Rite Max-E-Therm SFS Deliming

    Thanks, Paul. I'm assuming I will be replacing sooner than later, but didn't mind learning a thing or two by working on it (for free, save for some RTV and a few other supplies). So I did. Pulled everything apart per the YouTube video's instructions (which were really helpful), cleaned up what I could (got the gunk out of the manifold with a screwdriver, soaked the heating coils in vinegar to remove some of the lime, pressure washed stuff, etc.), put the unit back together and have it in service. Over the last few weeks, it's run much better. Still runs hotter exhaust temp than normal spec (now around 400-440F), but doesn't trip the 480F sensor. May not be the best situation, but at least lets me use it a bit longer.

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