Pentair Pool Pump GFCI trips

[rszimm]

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?

 

[JohnE]

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.

 

[texie]

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?

 

[FionaZuppa]

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

 

[GoldDigger]

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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[Ultrafault]

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

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[Sierrasparky]

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!

 

[Jraef]

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.

 

[Sierrasparky]

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

 

[FionaZuppa]

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.

 

[FionaZuppa]

and to verify, its a gfci cb and not a afci or combo cb ?

how funny, from 2015

Note to Hayward engineers, if you can't design a product that doesn't trip a GFCI in 2015 go work at a freaking McD's.

fyi, some time ago there was a post here asking about the ferrite ring in the bathroom fan unit. its there to suppress motor RF noise. ferrite rings on the hots may also help in pool pump gfi issues if RF is the cause.

and from what i can see, if the pump makes RF noise it cannot impact other safety equip. Pentair should be held responsible if their crud is creating noise that trips gfi's.

 

[Jraef]

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.

No it's not going to be triac based, it's a VFD.

Common mode noise is always going to seek to return to it's source. In this case, the source will be the DC bus of the VFD, the noise is being created in the motor windings by the VFD pulses and is expressed onto the motor frame. So it has to flow from the motor frame back to the VFD DC bus on the ground plane. Any restriction of that HF noise on the way means it bleeds out into other ground paths in trying to get back, that's where the issue lies with the GFCI. It sees that current flow on the ground path that is not accounted for in the power flow path and reacts to it, assuming it is leakage to ground (which in a way, it is). So driving a ground rod etc. is not going to change that.

Could Pentair have done a better job of designing the system so that this doesn't happen? Maybe. But we don't know that they didn't, and the root of the problem is that someone didn't follow the explicit instructions on wiring up the pump. For example they may have had detailed requirements for how the grounding was to be done, but it was installed like every other pool pump that the installer had done in the past and although it meets NEC requirements, it created a new problem.

 

[FionaZuppa]

but its likely not DC leakage? if its RF then there are several ways to try and squash it. how about adding a choke at the pump, ~1-2mH in size inline with the egc, along with ferrite ring? sure, a choke in mH in that size wire will be big. 150kHz & 1mH makes ~1kΩ

 

[bclumen]

I've been involved with the DC region's pool industry for 20+ years and have been witnessing Pentair VS pumps tripping GFCI breakers since they introduced the pumps to the market. Our company has a small department that specializes in electrical installation for pools and other outdoor related projects. We wire on average 200+ per year. I've used every brand breaker multiple times except GE. I don't have a lot of experience with Hayward since there are not a lot of pool builders using them but Pentair is by far the most frequently used followed by Jandy.

Pentair had Siemens make a breaker that they claim to trip at 6 ma instead of the 4-6 ma range. It is only approved for installation in the Pentair control system enclosures.
Jandy put out a service memo stating they've tested their VS pumps on all breakers (1" frame) and the Siemens proved to be the most reliable.
I've found that the Siemens results in less tripping with the Pentair and Stayrite pump (made by Pentair now) but not had many problems with the Jandy VS pumps.
I was using CHBR breakers but had to go back on 50+ pools last year to swap the CHBR GFI breakers with Siemens (I was able to return them to reduce that pain). I was put in touch with an engineer at CH who was knowledgeable of the issues with the VS pumps on the GFI breakers and he sent me a case. Some breakers from that case have been used on jobs close to us and sure enough they tripped.
Had another job with a brand new Stayrite pump and the existing CHCH GFI we connected it to tripped. Now installed a Siemens 60A hot tub disconnect and swapped the 260GFI with a 220GFI to hopefully correct the issue.

I've been told by a builder who have had several VS pumps tripping on the Siemens and the pumps replaced a few time under warranty that Pentiar will not warrant the pumps unless they install the Pentair breakers. They did that and the pumps are still tripping.

I've noticed that several of the jobs where VS pumps cause tripping are at the end of streets or on cul-de-sacs (near the end of the power company's line). I'm wondering if that may have something to do with this.

 

[czars]

I have had similar problems with Pentair and Hayward variable speed pumps. Hayward finally told me that the pump electronics puts noise back on the line that some GFCI breakers can not handle. For whatever reason, the Siemens GFCI breakers have not been bothered by the noise. There a likely ways to ID the noise and then filter it out, but all that takes time and costs money. For customers that do not have a Siemens panel to install a Siemens GFCI in, I install the proper breaker size and mfg into the existing (non-Siemens) panel and follow it with a 50A GFCI SPA panel to provide the GFCI protection. This has worked every time I have had the problem.

 

[Dennis Alwon]

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.

I bet they left you a different brand gfci.... This stuff is ridiculous. Hayward pumps say that only a Sq. D gfci works and another manufacturer says only Seimens will work.

When we do pools we find out from the pool company what brand is needed because it is a hassle to deal with later. May as well avoid trouble and now they can't blame you for the issue.

They need to fix the motors to work properly.

 

[FionaZuppa]

I have had similar problems with Pentair and Hayward variable speed pumps. Hayward finally told me that the pump electronics puts noise back on the line that some GFCI breakers can not handle. For whatever reason, the Siemens GFCI breakers have not been bothered by the noise. There a likely ways to ID the noise and then filter it out, but all that takes time and costs money. For customers that do not have a Siemens panel to install a Siemens GFCI in, I install the proper breaker size and mfg into the existing (non-Siemens) panel and follow it with a 50A GFCI SPA panel to provide the GFCI protection. This has worked every time I have had the problem.

my own spa, uses this same setup. 50A cb in main, 50A gfi Eaton in sub panel located near the hot tub. distance between sub and main is ~100ft in wire (buried in pvc). however, my spa does not have fancy speed control, simple two sets of pumps that run at low or full speed, but electronic controls.

just for the learning experience, i would stick a choke inline with the egc at the pump.

the makers could likely add a ferrite and choke and the problem would perhaps never surface.

 

[vincentvigil]

my own spa, uses this same setup. 50A cb in main, 50A gfi Eaton in sub panel located near the hot tub. distance between sub and main is ~100ft in wire (buried in pvc). however, my spa does not have fancy speed control, simple two sets of pumps that run at low or full speed, but electronic controls.

just for the learning experience, i would stick a choke inline with the egc at the pump.

the makers could likely add a ferrite and choke and the problem would perhaps never surface.

What size ferrite did you use?

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[bclumen]

I bet they left you a different brand gfci.... This stuff is ridiculous. Hayward pumps say that only a Sq. D gfci works and another manufacturer says only Seimens will work.

When we do pools we find out from the pool company what brand is needed because it is a hassle to deal with later. May as well avoid trouble and now they can't blame you for the issue.

They need to fix the motors to work properly.

Could not agree more.

 

[FionaZuppa]

What size ferrite did you use?

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i dont have a tripping issue.
my next step would be to FFT scope the lines near gfi to see what the RF/noise looks like.

but perhaps just those that snap-clamp on. $1.33 at allied. put them on the hots and egc.

and, have any of these lying around? just put the pri or sec winding in series with the EGC at pump, just as a test, see if the gfi tripping issue goes away. if it does then get a 1mH coil in proper awg size. 14ga and bigger will make a large coil, but if that's what it takes then so be it. a surplus store should have these old xfrmers for like $1.