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Thread: Heater Temperature Reading Does not Match Actual Water Temperature.

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    Heater Temperature Reading Does not Match Actual Water Temperature.

    We have a 2 1/2 year old SR400NA we use to heat our SPA. Last night the SPA would only heat to 94 degrees as reported by out Pentair Water Easy Touch controller. The water was lukewarm at best. I tried shutting off the breakers to all the pool equipment to see if that woul reset everything, but that did not help. I then went to the heater and looked at the display which was reporting the water temperature at 104 degrees (high-temp lockout). The service light is NOT lit, so it thinks everything is good. Is there an easy fix for this or am I looking at replacing the thermometer in the heater.

    Update:

    I went out and tried to heat the SPA again today and the SPA will only come up to 77 degrees while the number on the heater's display says 104 (I'm assuming that is the temperature the heater thinks the water is at).

    Thanks

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    Patrick_B's Avatar
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    Re: Heater Temperature Reading Does not Match Actual Water Temperature.

    Welcome to TFP!

    I have Pentair and always have to calibrate my controller to the heater, but we are only talking a few degrees at most. Sounds like the thermo in the heater is way off. I'm not sure of the brand, but I don't think most of them can be adjusted. Sorry I can't offer more help.
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    Re: Heater Temperature Reading Does not Match Actual Water Temperature.

    Could be several things. First I would suspect the thermal regulator in the heater. Between the inlet and outlet of the heater is where this part is at. You unscrew it and pull out the thermal regulator. If when you unscrew it, it won't pull out using little effort, then the bypass valve in the neater is broken and needs to be replaced. A but more work to fix that. However, if you can pull the thermal regulator out and it's all corroded, replace it and then see if the heater operates as it should.
    Paul
    http://www.gastekservices.com 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: Heater Temperature Reading Does not Match Actual Water Temperature.

    Guys, thanks for the input. I have a pool guy coming out to look at a separate issue and will have him check this out, I just want to have an idea what the issue could be. As with any gas appliance I would always turn the gas off before tinkering. Through the school of hard knocks I learned to be pretty cautious about stuff I'm unfamiliar with.

    Thanks again.

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    Re: Heater Temperature Reading Does not Match Actual Water Temperature.

    Quote Originally Posted by dt03457 View Post
    Guys, thanks for the input. I have a pool guy coming out to look at a separate issue and will have him check this out, I just want to have an idea what the issue could be. As with any gas appliance I would always turn the gas off before tinkering. Through the school of hard knocks I learned to be pretty cautious about stuff I'm unfamiliar with.

    Thanks again.
    Its more than likely the temperature sensor in the heater. Its a relatively inexpensive part and very easy to replace.

    - - - Updated - - -

    Quote Originally Posted by ps0303 View Post
    Could be several things. First I would suspect the thermal regulator in the heater.ld.
    Thermal regulator failures typically lead to the high limit kicking the heater off, or the stack flue sensor ( not enough water to cool down the heater).
    20X40 30,000 gallon gunite pool

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    Re: Heater Temperature Reading Does not Match Actual Water Temperature.

    Quote Originally Posted by racket View Post
    Its more than likely the temperature sensor in the heater. Its a relatively inexpensive part and very easy to replace.

    - - - Updated - - -



    Thermal regulator failures typically lead to the high limit kicking the heater off, or the stack flue sensor ( not enough water to cool down the heater).
    Not all the time.
    Paul
    http://www.gastekservices.com 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: Heater Temperature Reading Does not Match Actual Water Temperature.

    What would be the tolerance? My 6yr old Starite SR400 is about 6 degrees higher. Few months ago I replaced the thermal reg and thermister on a separate issue. Where would you find temp sensor in the heater?
    18k free form IG w/spa (4 jets), Paramount in floor cleaning system, Starite system 3 filter, Jandy 2hp ePump, Sta-Rite SR400LP Maxi-therm propane heater, Jandy aquapure/apurem 1400 SWCG, Jandy automation PS4 w/PDA, IntelliBrite 120v 5-G LED pool & spa lights, 2" piping and (3)4x12 (5)4x10 Fafco Sunsaver Solar Panels.

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    Re: Heater Temperature Reading Does not Match Actual Water Temperature.

    My 10 year old Jandy LT400 would heat the spa to 90F degress (it was set to 102F) and then stop heating. The fan and the pool pump kept going but the heat would not come back on. If I would shut everything down and do a restart then it would continue heating to 94F and stop heating again.

    I replaced just about every sensor including the thermistor, high and low temp switches and exhaust temp sensor. Still no change. This week I tried to the spa heater again. When it shut down at 90F I disabled the pool actuators and switched the P4 Aqualogic to the pool setting. I previously also set the pool setting to 102F. The heater immediately restarted and the spa temp rose the 102F setting.

    I'm not completely thrilled about having to "trick" the system like this but now I feel the problem is more than likely the LT400 temperature control board. For $600-800 they want for a replacement I'll keep dancing around the system for now. You might try this with yours to see what happens.
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