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Trying to add a surge protector at a sub panel by pool. The 240 circuit runs from the main load panel on side of house to sub panel by pool - red, black and green only - to a disconnect and the pump. The surge protector (Intermatic PS3000) has two black and one white wire only. No other wires. I was planning to connect the two black wires to the red and the black from the 240 circuit at the disconnect, but am stumped with where to attach the third wire.

I am adding a whole house surge protector, but also one at the pump for extra protection because the variable speed pump has an on board electronic unit that is more sensitive and according to many reviews, can be troublesome. Kind of like adding a surge protector next to electronics inside.

I understand that at the main load center the white/neutral would go to the ground/neutral bus bar, but that according to code, at a sub panel, it should go to a neutral bus that is isolated from the ground bus. Otherwise, as I understand it, you can end up with neutral current on the ground wire.

At the sub panel, the ground bar is bonded to the rebar in the pool. Intermatic says they get this question all the time and that they tell everyone to connect the white wire to the ground at the sub panel and tape it green. Intermatic tech support even says they are trying to get the color of the wire changed to green by production. Two local electricians have said this is fine also, even though it might not be 100% code. I am asking here because I believe the advice is very considered and expert, and I want to be safe and follow code.

There is also a 110 circuit running from the main load center directly to the sub panel. This circuit has a neutral on it. A ‘professional’ pool installer which sets up pumps routinely said that he regularly grabs neutrals from other circuits and that it would be fine to connect the white wire from the surge protector to the neutral on the 110 circuit. This makes me a little nervous as it seems like I would be mixing a 110 circuit with a 240 circuit.

I would really appreciate any thoughts on this. Thank you.

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    That's a really good question -- we'll probably need to do quite a bit of digging into it, considering that Intermatic doesn't provide much documentation-wise.
    – ThreePhaseEel
    Commented Jul 9, 2016 at 4:08
  • Minor confusion: will a surge protector actually do something useful in this application?
    – keshlam
    Commented Jul 9, 2016 at 8:02

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Good question! DOC - to answer your question, (for 240 volt application) the two BLACK wires go to a 2-Pole 20A breaker and the white goes to the ground bus or a bonded neutral bar. Here is a cut sheet for a unit similar to yours (and similar to those that we install on a daily basis:

http://www.five-two-one.com/pdf/LT521SPD_Web.pdf

Hope this helps you!

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  • The spikes from the surge protector (white) need to be connected to ground not neutral. Your ground plane for the pool would be the closest and do the most good. +
    – Ed Beal
    Commented Jul 9, 2016 at 15:20
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    Yes Ed, thank you for seeming past my ambiguity. I stated that the white goes to the ground bus OR BONDED neutral. Of course, the only place the neutral bar should be bonded to the ground bar is in the MAIN panel. With that being said, DOC's sub-panel surge protectors' white wire should indeed be mounted on the ground bar of the sub-panel as the neutral bar in this panel is not bonded.
    – Michael Carolan
    Commented Jul 10, 2016 at 14:34

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