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Thread: Heater won't stay running, any suggestions?

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    Heater won't stay running, any suggestions?

    We have a brand new pool last September. had pool company winterize pool, and open it up this spring. they wouldn't touch the heater as part of the opening which I didn't find out about until after the fact. Told me I could just turn it on as the home owner. Turned heater on, it comes on fine, gas is on, it starts to heat up, you feel the hot exhaust, it runs for between 10 and 20 minutes max, and then the "service heater" light comes on.

    Spent the past week trying everything I could think of to get it work. The manual indicates this could be a low flow issue, so I've tried what little I can think of to ensure proper flow. Today I took apart the 3 stage filter entirely, washed out all the filters, washed the sand and silt out of the bottom, etc. to see if that would help, no luck at all.

    It's a Pentair MasterTemp Pool and Spa Heater, worked great last year for the 2 months we had it on, not sure if there is any pool opening heater maintenance I've missed along the way? The pool company has called a certified natural gas installer to come and look at it, it's a holiday in Canada this weekend, so won't see him until at least Tuesday if we're lucky, was really hoping to enjoy the pool over the long weekend.

    Only other thing that's different this year over last is that the gauge on the filter is showing zero, and it did show pressure last year. The pool guy commented on it (after I pointed it out) and confirmed he didn't think it was working and likely needed to be replaced. When I cleaned the filter and put it back together. I had the release valve open until the water filled the filter and then closed it, so I know there is water in the filter, but wondering if maybe there isn't enough overall pressure in the system, which could explain why the pressure valve is showing zero, and why the heater is giving the "service heater" error, one of the symptoms that can cause this is low flow.

    any thoughts on other things I can check, try out, look further in to? let me know, appreciate any insights anyone might have.

    Enjoy the weekend,

    4440 Gallons - Intex 48" x 15'
    Intex Sand Filter Pump Model SF20110 - 2650 gph
    AG - June 2011

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Heater won't stay running, any suggestions?

    Welcome to TFP!

    There are unfortunately quite a number of possibilities.

    Check the strength of your return jets. If the return jets feel strong then it isn't flow problem. If there is a flow problem, check the skimmer basket(s), pump strainer basket, look under the pump strainer basket and feel around inside the pump to see if there is any debris blocking the impeller. Also check for valves that might be in the wrong position.

    It is very common for pressure gauges to fail over the winter, just replace it and don't worry about it unless the new one shows an unusual pressure.

    One common way heaters have problems is when debris accumulates inside the fire chamber. That might just be fallen leaves, or animals might have nested inside. See if you can access the burner chamber and blow or vacuum it out.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    In the Industry
    ps0303's Avatar
    Join Date
    Jul 2011

    Re: Heater won't stay running, any suggestions?

    One thing to do, if you want to, you could take the top off the unit and flip it over and there are a set of LED lights on the back that could tell you whats wrong. Maybe during the winter a mouse or something took up residence in the unit and chewed wires as well. Any number of things. Take the front panel off if you haven't already and inspect for things inside like nests and then remove the wing nuts from underneath the top, one in each corner, and flip it over. Turn it on and see what LEDs light up when it goes into "service heater" mode.

    These units have sealed can type of setup so it's very hard and extremely unlikely something go into that area. Hopefully there wasn't a breach in the heat exchanger allowing water to fill the canister where the burner is located.

    Those filter gauges are garbage for the most part. After a year they usually fall apart, get water in them, or something that disrupts their reading. You should be able to get one fairly easily at a home improvement store.

    Here is a link to the manual if you don't have one. ... erTemp.pdf

    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.

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    Re: Heater won't stay running, any suggestions?

    Thanks for the suggestions, guess i'll be doing a bit more investigating tomorrow!

    4440 Gallons - Intex 48" x 15'
    Intex Sand Filter Pump Model SF20110 - 2650 gph
    AG - June 2011

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    Join Date
    Aug 2014
    Canton MI

    Re: Heater won't stay running, any suggestions?

    I had the same problem with my Mastertemp heater. Had the pool for a year and then right around 80 degress would cycle on/off. Ended up being the thermo regulator. Quite easy to replace and was under warranty. These heaters seem to have that problem, very finicky with chemical balance. It seems to "rust" out the regulator and then it wont slide and gets stuck, then heater gets too hot and shuts off. Once it cools it starts up again. Easy to remove on the back of the heater to check it out though. See my previous post to see if your problem is like this --> one Just google "Mastertemp and thermo regulator". I do have a salt water pool and it seems to happen more to those with salt water. Makes me consider having PB replace as the thermo regulaotr has now quit working this year already and needed to be repalced. (Chemicals are all in balance).
    25K inground gunite with raised spa. Full Pentair products - Mastertemp 300 Gas Heater , IntelliBrite 5G Pool Lights (2), 1X Spa LED Light, VS Intelliflo Pump, Intellichlor SWG, 2 waterfalls and bubblers w/ seperate pump, sunshelf

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