7.5 hp 230 volt trips 60 amp GFCI breaker

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Besoeker said:
But fine they are not.
According to the op:

That does not sound fine to me.

Again from the OP:


Same comment.
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For whatever reasons it appears all but Siemens or the special issue CBs of the pump mfg have a problem. I've had Leviton GFCI devices that would trip with a single 6 lamp HO fixture connected. Install a CWD GFCI device and no problems. IDK why, just what.
 
The issue is, these are NOT actually "single phase" motors; they are 3 phase motors that have a BUILT-IN VFD that converts a single phase FEED to the 3 phase that the pump needs. Then the problem is that the VFD is creating enough Common Mode noise that the 5mA required trip level for a GFCI is activated. The issue of VFDs causing GFCIs to trip has been known for years, but because GFCIs only apply to single phase services, this has only reared its head recently when Pentair (and now others) started shipping these VFD powered pumps for residential swimming pools.

UL REQUIRES that ANY breaker listed as a GFCI trips at 5mA nominal, but no more than 6mA. But CM noise from a VFD will be at a much higher frequency and actual leakage current from the fundamental (60Hz). The issue with the Siemens breakers is just the result of a slight design variation that HAPPENS to be less sensitive to CM noise signals, likely because they have a different way of filtering out HF current in their GF sensor, so they don't trip as easily from this.

There have been reports of people getting around this by adding a shielded isolation transformer ahead of the pump and grounding the shield so that the CM noise doesn't make it back to the breaker. There have also been mentions of adding ferrite beads to the wires going to the pumps as a way to suppress it too, I have never heard back if that worked or not.

PS: because the VFD will also "soft start" the motor, the breaker never sees the motor starting current.
 
Jraef said:
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There have been reports of people getting around this by adding a shielded isolation transformer ahead of the pump and grounding the shield so that the CM noise doesn't make it back to the breaker. There have also been mentions of adding ferrite beads to the wires going to the pumps as a way to suppress it too, I have never heard back if that worked or not.
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I could see an inspector arguing that since a real ground fault on the pump side of the isolation transformer will also not trip the GFCI, the required GFCI protection for the pump or the pump outlet is not being provided.
 
thank you all for your input

just to clarify, this is a commercial swimming pool application.

according to the 2014 NEC article 680.21(C) any single phase circuit supplying power to a swimming pool pump motor has to have GFCI protection.

in addition to this code, the NC Administrative Code and Policies has issued an amendment (161213 Item B-5) stating, " whenever a Pool pump motor requires replacing and the existing branch circuit or receptacle providing power to the pump motor does not provide ground fault circuit interrupter protection for personnel, the branch circuit or receptacle shall be updated to provide GFCI protection.

this being said, any time we go into a swimming pool pump room and work on a pump, we check to see if the circuit is GFCI protected. a large percentage of them are not and we are updating this issue. the problem we are encountering is when we install a GFI breaker for a 7.5 hp pump. the GFI trips immediately when the pump is started.

please note the following specs

1. main panel GFCI breaker is installed in is a Cutler Hammer type BR
2. GFCI breaker being used is a Cutler Hammer 60 amp 2 pole GFCI type BR
3. a motor starter is wired after the GFCI breaker utilizing a thermal overload device. the control circuit is isolated from the gfci breaker and has a different source of power. pump is controlled by an ON/OFF button station on the motor starter.
4. pump motor is a us motors 7.5 hp 230 volt 30.4 amp I phase 3600 rpm and is on a Pentair EQ series pump.

this pump was tested with a regular cutler hammer 60 amp 2 pole breaker before we began any work. the pump ran fine with a standard breaker.
once gfci breaker was installed and the ON button was pushed, the gfci breaker trips immediately.
if we disconnect the motor terminal wires from the branch circuit wiring the gfci will remain on
we have went through all the capacitors and tested them with a cap checker and they all test fine
the in rush amp draw is around 130 amps when the ON button is depressed and the motor attempt to run.

so again, I am asking why does the GFCI breaker trip?
 
Hopefully you had not had an opportunity to read Jraef's excellent post (#23).
From my viewpoint he gave a very valid explanation as to why.
The solution does not seem to be that obvious.
 
folks please understand that we are not dealing with a 3 hp intelliflo or similar type pump. there is no vfd or vsd involved here. it is truly a single phase motor.
someone mentioned previously that they heard of Pentair pumps tripping gfci breakers! this is NOT the same application.
 
stephenweyant said:
folks please understand that we are not dealing with a 3 hp intelliflo or similar type pump. there is no vfd or vsd involved here. it is truly a single phase motor.
someone mentioned previously that they heard of Pentair pumps tripping gfci breakers! this is NOT the same application.
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Supply a Siemens sub from the BR panel using a 70 amp BR breaker. Supply your circulating pump from that sub via the preferred Siemens GFCI.

Or

Plug the Siemens breaker into your BR panel and see if it holds. If it does, see above.

edit, ok, they don't have a preferred breaker. Try it anyway.
 
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Yeah, if your motor has capacitors, then it's a true single phase motor. So the VFD issue will not be in play.

I notice in the poop sheet that this is a "premium efficiency" motor and another known issue with them is that in order to get higher efficiency, they lower the impedance and winding resistance, resulting in higher inrush currents. So the fact that it hold in under a "regular" 60A breaker and trips on the GFCI breaker might be due to the breakers having different instantaneous trip curves.

Or it could be that the higher inrush and starting capacitor surge causes a high DC offset in the AC line that is causing the GFCI to trip.

Also, since this has an external OL relay on the starter, is that a solid state OL relay by chance? Sometimes it's hard to tell now, and the "self powered" SSOLs have a little power supply on them that might be a source of CM noise too. In addition, some motor starter coils are now also solid state, so they too have a power supply that can create CM noise. Just another guess, because now I've got nothing else. But it comes down to why a standard breaker would not trip and a GFCI breaker will; it usually comes down to SOMETHING being misinterpreted by the GFCI sensing circuit.
 
@Jraef
thank you for the reply.
the motor starter is not solid state so no electronics at all. bi metal heaters and regular type coil.

since im having issues with multiple motors at different facilities, the only common factor so far is the Cutler Hammer GFCI breaker. I will try to install another brand of breaker and see if its any better.

is there an alternative method of providing GFCI protection to motors? something rated more than 60 amps? I see this as a real issue according to NEC regulations. how can you use a 60 amp GFCI breaker on a 10 hp single phase pump motor?
 
@Jraef

I was looking at some other GFCI devices and they do offer a Class C device with higher mA ratings. however im not sure if this would be appropriate. the NEC doesn't specify, only stating it as GFCI protection for personnel. Littlefuse and NSS both offer these and it could be an option?
 
kwired said:
presuming both have same instantaneous trip point.



GFCI in the places where NEC is used is a device that responds to leakage current outside the intended circuit conductors, listing requirements for such devices want them to trip if leakage is more then 4-6 mA. They do not respond to short circuits or overloads, though there are types that are incorporated into circuit breakers - but the GFCI function is still a separate portion of those units and when they trip on short circuits or overloads that is the thermal-magnetic components that is tripping.

OP needs to somehow determine if his GFCI breaker is tripping on GFCI functions or thermal-magnetic functions.
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>>


OP needs to somehow determine if his GFCI breaker is tripping on GFCI functions or thermal-magnetic functions.
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For a "TEST ONLY", if the OP disconnected the white pigtail wire on the gfci breaker from the neutral bar in the panel would that disable the gfci function of the breaker from operating?
IF so, then if the breaker tripped instantly on startup it would be caused from high inrush current on startup and therefore the T/M unit in the breaker caused the breaker to trip open.
 
GoldDigger said:
Post #23 tells you exactly why.
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stephenweyant said:
@Jraef

I was looking at some other GFCI devices and they do offer a Class C device with higher mA ratings. however im not sure if this would be appropriate. the NEC doesn't specify, only stating it as GFCI protection for personnel. Littlefuse and NSS both offer these and it could be an option?
Click to expand...
GFCI to NEC is the class A 6mA protection intended for personnel protection. Levels higher then 6mA are GFP, intended for equipment protection.

So when NEC says GFCI it means the 6mA personnel protection devices. Actually NEC doesn't typically use the GFCI acronym but rather the full term "ground fault circuit interrupter". Most places where they do use the GFCI acronym is in parenthesis following the use of the full term - "ground fault circuit interrupter (GFCI)".
 
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