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Thread: Pentair Pool Pump GFCI trips

  1. #1
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    Pentair Pool Pump GFCI trips

    Brand new 3HP Pentair pool pump, computer controlled, variable speed. Connected via 2 pole GFCI breaker (no load neutral to the pump). Nuisance trips about once per day. The pool company tells me this is so common that they generally swap out the GFCI breaker as soon as the inspection is complete with a standard 2 pole breaker. They give me some gobbledygook about inductive loads, blah blah. Being a EE and knowing that GFCIs are pretty simple (just run all the load wires through a coil and measure the current coming off that to make sure all the current going out one line comes back on one of the others), this just doesn't sit well with me. Inductive loads or no; computer controlled or no, if current is on one line and not coming back on another, it's by definition going through either the grounding conductor or into the actual physical ground. I suppose some high speed switching of the motor from the variable speed controller could theoretically induce a small amount of current in the case or the grounding conductor, but that would seem to be a design fault in the pump.

    Anyone else run into this?

  2. #2
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    Quote Originally Posted by rszimm View Post
    Brand new 3HP Pentair pool pump, computer controlled, variable speed. Connected via 2 pole GFCI breaker (no load neutral to the pump). Nuisance trips about once per day. The pool company tells me this is so common that they generally swap out the GFCI breaker as soon as the inspection is complete with a standard 2 pole breaker. They give me some gobbledygook about inductive loads, blah blah. Being a EE and knowing that GFCIs are pretty simple (just run all the load wires through a coil and measure the current coming off that to make sure all the current going out one line comes back on one of the others), this just doesn't sit well with me. Inductive loads or no; computer controlled or no, if current is on one line and not coming back on another, it's by definition going through either the grounding conductor or into the actual physical ground. I suppose some high speed switching of the motor from the variable speed controller could theoretically induce a small amount of current in the case or the grounding conductor, but that would seem to be a design fault in the pump.

    Anyone else run into this?
    I'm experiencing this now. I don't wire a lot of pools (1-3/ year). Homeowner said pool company left me a replacement breaker to change it out. I haven't been there yet and assumed it was a replacement GFCI breaker. I'll be going there tomorrow and will see what they left me.

    I'm interested to hear others' experiences.
    Formerly J Erickson as username.

  3. #3
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    Quote Originally Posted by rszimm View Post
    Brand new 3HP Pentair pool pump, computer controlled, variable speed. Connected via 2 pole GFCI breaker (no load neutral to the pump). Nuisance trips about once per day. The pool company tells me this is so common that they generally swap out the GFCI breaker as soon as the inspection is complete with a standard 2 pole breaker. They give me some gobbledygook about inductive loads, blah blah. Being a EE and knowing that GFCIs are pretty simple (just run all the load wires through a coil and measure the current coming off that to make sure all the current going out one line comes back on one of the others), this just doesn't sit well with me. Inductive loads or no; computer controlled or no, if current is on one line and not coming back on another, it's by definition going through either the grounding conductor or into the actual physical ground. I suppose some high speed switching of the motor from the variable speed controller could theoretically induce a small amount of current in the case or the grounding conductor, but that would seem to be a design fault in the pump.

    Anyone else run into this?
    This is a known issue with these pumps. I think there are even other threads about this. I seem to recall that Pentair claims they do not have these issues with Siemans GFCI. I have a novel idea, maybe someone needs to take Pentair to task and force/shame them into investigate and fix what the issue is here. Just taking the coward way out and telling people that they must use a certain brand would not be acceptable to me. What does one do if Siemans is not an option for the panel that is installed? OK, add a subpanel for the Siemans breaker. Who's paying for this?

  4. #4
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    why not amp clamp the egc (take off gfi), see how their stuff is bad, then you can send a nasty-gram to pentair.

  5. #5
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    Quote Originally Posted by FionaZuppa View Post
    why not amp clamp the egc (take off gfi), see how their stuff is bad, then you can send a nasty-gram to pentair.
    Since a pool pump may have several routes to ground (and hence to POCO return) other than the EGC, you really need to simultaneously clamp hot(s) and neutral, just as the GFI does.

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  6. #6
    Is it possible that the rectifier has movs installed that are leaking to ground?

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  7. #7
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    Yea but nothing should be flowing to Ground!

    They probably have is some circuitry that has a component that has line to ground current flow....... Maybe a MOV or something.

    Oooops I was late on that reply!

  8. #8
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    The issue is, these newer Pentair pool pumps have a built-in VFD to a 3 phase motor (the VFD accepts single phase, puts out 3 phase). VFDs produce a lot of high frequency (above 150kHz) common mode noise if not installed exactly perfectly with regard to grounding between the drive and motor. So in some GFCIs, that HF CM noise gets detected and acted upon. The Siemens GFCI breakers apparently discriminate against that HF CM noise and don't trip as easily. So you can either replace the GFCI with a Siemens version, or you can add a shielded isolation transformer between the GFCI and the pump.

    I have HEARD (but not had the chance to try) that increasing the size of the ground connection inside of the pump between the drive and the motor can help, because the HF CM noise travels on the surface of conductors, not deep into them. By increasing the conductor size you are increasing the surface area. That's one of the reasons to use Shielded VFD cable, it's an alternate path for CM noise to travel. In this case because the VFD is close coupled to the pump motor, that doesn't apply here.
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  9. #9
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    Quote Originally Posted by Jraef View Post
    The issue is, these newer Pentair pool pumps have a built-in VFD to a 3 phase motor (the VFD accepts single phase, puts out 3 phase). VFDs produce a lot of high frequency (above 150kHz) common mode noise if not installed exactly perfectly with regard to grounding between the drive and motor. So in some GFCIs, that HF CM noise gets detected and acted upon. The Siemens GFCI breakers apparently discriminate against that HF CM noise and don't trip as easily. So you can either replace the GFCI with a Siemens version, or you can add a shielded isolation transformer between the GFCI and the pump.

    I have HEARD (but not had the chance to try) that increasing the size of the ground connection inside of the pump between the drive and the motor can help, because the HF CM noise travels on the surface of conductors, not deep into them. By increasing the conductor size you are increasing the surface area. That's one of the reasons to use Shielded VFD cable, it's an alternate path for CM noise to travel. In this case because the VFD is close coupled to the pump motor, that doesn't apply here.
    Very interesting.
    Thanks

  10. #10
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    modern day MOV's should be leaking in the uA range, not mA.

    HF noise on the line is very interesting. i would be curious to see the results if you tied the EGC to a 10ft ground rod very close to pump EGC.
    and/or
    tie a 600v 0.1uf with a 10k resistor in series from each 240 hot leg to a ground rod, as close to pump as possible.

    the pump is electronically controlled multi-speed? perhaps triac based, and if they switch fast that noise is a pita to some gfci's.

    next best thing is to scope the wires in FFT mode (load side) close to the gfci, see if you can find HF there. you can isolate using the same RC snubber.

    but considering pool gear needs gfi, pentair should have their act together if their crud is creating HF noise on the wires.
    Last edited by FionaZuppa; 07-05-17 at 03:08 PM.

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