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Thread: Pentair Mastertemp 400 - No Power?

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    Pentair Mastertemp 400 - No Power?

    Hi folks,

    First post. I have a Pentair Mastertemp 400 heater. Last week we turned on the heater to heat the spa and the heater did not ignite. I went over to the equipment and see no power at the control panel on the unit. I did see a plastic bucket had blown over and was laying on the exhaust vent. I can see a small amount of the bucket melted due to the exhaust heat, probably from the last time we used the spa. Is there some kind of thermal overload breaker or any circuit breaker within the unit itself. I have checked the sub panel and there are no beakers thrown there. What else would cause no power at the unit itself?

    Any ehl would be appreciated.

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    4knights's Avatar
    Join Date
    Aug 2012
    NE Kansas

    Re: Pentair Mastertemp 400 - No Power?

    Welcome to TFP, I can't answer your question but here is a link to your manual and troubleshooting.
    Ron- Kansas. IG fiberglass, Riviera 30 Freeform 13600 gallons,
    EasyTouch 4 w/IC20 SWCG, Pentair Whisperflo 1hp, 2 speed 220 pump, Hayward ProGrid 4820 DE filter using Eco Klean instead of DE, 2 Savi Melody 12v 5 color LEDs, Raypack 266k btu millivolt heater, Arctic Armour Mesh custom safety cover (Total self Install) TF-100 test kit w/Magic stir.

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    Join Date
    May 2010
    Yuma AZ

    Re: Pentair Mastertemp 400 - No Power?

    Welcome to TFP
    Do you have any LED lights on your control panel showing?
    Is the "service Heater or Service System " indicator lights on?
    I recently fixed my Mastertemp 400 but my problem was the HSI-igniter.
    Pentair has an excellent customer service department. 800-831-7133 (CA) I'm not sure if they are open on weekends but they will help you with diagnostics of your system. You will need a multimeter and a few small tools.
    The system has a stack flue sensor which may have been triggered due to the obstruction of exhaust gases
    10,000 gallons IG Freeform, 8ft raised spa,pebble finish
    FNS 60 Sqft DE Filter,2HP Whisperflow for Pool/Spa filtering
    2HP Whisperflow for Spa jets
    1HP Whisperflow for Waterfall
    Master Temp 400,000 Btu Heater

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    Re: Pentair Mastertemp 400 - No Power?

    No LEDS lighting up at panel.

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

    Re: Pentair Mastertemp 400 - No Power?

    The next step is to get out a multi-meter and see if power is present at the input terminals on the heater.
    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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    Re: Pentair Mastertemp 400 - No Power?

    OK I have power to the unit and 24 volts coming out of the transformer. Nothing happens when I turn on the heater. No blower, heater does not start nor is there anything lit up on the control pad. What's the next thing to check? I see a few sensors, should I start bypassing them to see what happens?

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    In the Industry

    ps0303's Avatar
    Join Date
    Jul 2011

    Re: Pentair Mastertemp 400 - No Power?

    There is a fuse inside the control panel in the heater. Check and see if it is blown. I believe is 1 1/4 amp fuse. Good luck finding them. If you do replace it and it blows right away when you turn it on, then you probably have a short on the systems board of which then the board needs to be replaced.
    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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    laurin1's Avatar
    Join Date
    May 2015
    Flower Mound, TX

    Re: Pentair Mastertemp 400 - No Power?

    I'm having a similar problem. Power on the terminal board seems right. I am getting 240 on red/black and 120 on black/yellow and red/yellow now.

    I have tested the fuse on the terminal board for continuity. How do I test the voltage coming off of the transformer?

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