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Thread: Changing a DPST to SPST Timer

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    Pointyhead's Avatar
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    Changing a DPST to SPST Timer

    My Timex timer broke recently (plastic shaft inside snapped) and no longer will spin. I bought an Intermatic T101M as a replacement. Beside the fact that mechI got a super deal on it on eBay, but didn't realize that it was a SPST as opposed to the DPST that the Timex is. Which means that the terminal strip is different. On the DPST, there are 4 terminals, 1-4, with a black and white set coming from the breaker box and a black and white set going to the pool pump. The new timer only has 3 terminals, the A post and 1 and 2. How exactly should this be wired? Anybody else have this problem?
    10 year old 18x32 inground, vinyl liner 1 year old, 25,000 gallon Grecian, Hayward ST244 Sand Filter, 1hp Hayward pump, Diving board, Side Steps, Koolcrete decking located in middle [s:37hekvij]earth[/s:37hekvij] Georgia.

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    JasonLion's Avatar
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    Re: Changing a DPST to SPST Timer

    You need to get a different timer if you need a DPST switch. The T101 only switches a single line. You need a T104 if you want to switch two lines.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Changing a DPST to SPST Timer

    Is your pump a 240 volt or 120 volt unit? I am inclined to think 240.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Pointyhead's Avatar
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    Re: Changing a DPST to SPST Timer

    The pump is 110. I just changed it out this spring. It's a Hayward 1.5 super pump. In fact, I don't have any 220 lines in my breaker box.
    10 year old 18x32 inground, vinyl liner 1 year old, 25,000 gallon Grecian, Hayward ST244 Sand Filter, 1hp Hayward pump, Diving board, Side Steps, Koolcrete decking located in middle [s:37hekvij]earth[/s:37hekvij] Georgia.

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    JasonLion's Avatar
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    Re: Changing a DPST to SPST Timer

    When using 115 volts, there is almost never a reason to use a DPST switch. Do you know what was being switched on each pole of the old switch?
    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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    Pointyhead's Avatar
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    Re: Changing a DPST to SPST Timer

    Quote Originally Posted by JasonLion View Post
    When using 115 volts, there is almost never a reason to use a DPST switch. Do you know what was being switched on each pole of the old switch?
    No, there's just the 4 insulated wires coming in to the timer box, 2 white and 2 black (plus 2 grounds). The only thing on the circuit is the pool pump.
    10 year old 18x32 inground, vinyl liner 1 year old, 25,000 gallon Grecian, Hayward ST244 Sand Filter, 1hp Hayward pump, Diving board, Side Steps, Koolcrete decking located in middle [s:37hekvij]earth[/s:37hekvij] Georgia.

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    Re: Changing a DPST to SPST Timer

    Quote Originally Posted by Pointyhead View Post
    No, there's just the 4 insulated wires coming in to the timer box, 2 white and 2 black (plus 2 grounds). The only thing on the circuit is the pool pump.
    Sounds to me that they were switching the neutral for some reason?? Without being there with a meter it's hard to tell.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Changing a DPST to SPST Timer

    Looks like the Neutrals connect to the A terminal, line to terminal 1 and load to terminal 2
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Pointyhead's Avatar
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    Re: Changing a DPST to SPST Timer

    Quote Originally Posted by danpik View Post
    Looks like the Neutrals connect to the A terminal, line to terminal 1 and load to terminal 2
    That's what I'm thinking. The clock motor is pre-wired to A (neutral) and hot to Terminal 1.
    10 year old 18x32 inground, vinyl liner 1 year old, 25,000 gallon Grecian, Hayward ST244 Sand Filter, 1hp Hayward pump, Diving board, Side Steps, Koolcrete decking located in middle [s:37hekvij]earth[/s:37hekvij] Georgia.

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