Square D QO120DF tripping in blocks of four in several houses.

[11bgrunt]

POCO has 8 houses on one 100kV padmoount transformer.

These houses have the same home builder and looks like the same electric sub. The oldest house in this group is 2016.

The layout to each house is POCO URD to meter & 200A panel then four wire to the 100A sub panel. The electrician’s workmanship is satisfactory and would have passed a municipal inspection.

At random times a block of four QO120DF breakers, in the panel next to each vertically, trip simultaneously. Dishwasher, disposal, washing machine and refrigerator.

Different homeowners report the same symptoms. Maybe four times in the past month. No correlation to any homeowner activities. The red herring: Homeowner #1 has a pool with a double pole GFCI breaker for the pool. When the four DF breakers trip at his house, he finds the pool breaker has tripped.

In the subpanels there are AFCI, one GFCI, another DF and two standard QO combination breakers that have not tripped when the four DFs trip. The are not 100A plug on neutral panels.

The padmount transformer was inspected, checked with a SuperBeast to force a neutral imbalance and the NEV was checked around the transformer.

Square D time saver diagnostics tripped a single DF breaker in house # 1 instantaneously.

An instant trip indicates Arcing to ground, Shared neutral, Grounded neutral or Ground fault.

A PMI voltage recorder was set at house #1 today. The recorder will be pulled after the next event.

Our history with AF, GF & DF breakers is the problems occur in new construction and usually not with QO.

I don’t see the utility power being the cause but having a common grounded conductor probably does.

 

[zbang]

Kinda standard checks-
are all the panels properly bonded, only one N/G bond per house, good grounding electrodes & wiring, etc.
Are there metallic water or sewer lines?
(Large radar installation within 5 miles?)

 

[11bgrunt]

RF influence has been checked. Houses have many years with no issue. Water and sewer will all be plastic. Wiring methods look good.

 

[hillbilly1]

Shouldn’t have affected the pool gfi, but I’ve had a bad poco connection at the transformer cause multiple arc faults trip within seconds of each other, and they were Square D QO. Kinda surprised the poco put in a 100 kva transformer. Usually they go smaller. Might have them open it up and inspect connections.

 

[11bgrunt]

The policy is 12.5 kVA per house when serving 8 houses. The transformer was checked.

 

[kwired]

Is the mentioned Dishwasher, disposal, washing machine and refrigerator or even the pool pump variable speed?

GFCI's don't like to play well with variable speed drives and their high frequency leakage and can even sometimes trip other GFCI's that are not supplying those items.

 

[jimport]

A few years ago we had an issue with QO breakers tripping even when the appliance was not in use. Turned out to be a signal issue from the power company.

 

[hillbilly1]

The policy is 12.5 kVA per house when serving 8 houses. The transformer was checked.

Down here they will run three or four houses off a 10. Up north, they have 7-8 houses off a 10 in old neighborhoods, but usually no A/C, and heat is natural gas. Any splice boxes?

 

[11bgrunt]

Thanks for the comments.
In this part of Texas, summers can be brutal. 105F in the afternoons.
These are large houses with large air conditioners.
If I was working a complaint for one house, i think the troubleshooting method would be different. In this case, houses that have nothing in common except the POCO transformer connections have similar symptoms. The appliance motors have grounding bonds. Maybe one motor is leaking above the GFCI standard and raising the voltage on the neutral? There is no report of any appliance not working normally.
Why only four of the DF breakers and not all of the DF or the GFCI in the subpanels?
The URD runs are straight pulls except the run crossing the street. Two runs, two houses on each run.
The POCO AMI is RF for the majority. They were forced to keep the PLC system active because of meter supply shortages. PLC does put a little spike in the sine wave, but the houses would have been exposed to that since they were new.
When the voltage recorder is pulled, maybe there will be a clue there. Schneider says there is a ground fault and the DF breaker is working fine.
I am still open to any suggestions. Tomorrow I will use my test board to see if a condition can be created to cause DF to trip on command. Arcing motors didn't trip them and resistive/open neutrals didn't either.
A local EC will not use DF because of past experiences that were never resolved. If the circuit in new construction needs dual function, it gets an AFCI breaker and a GFCI feed through receptacle downline..

 

[mtnelect]

This might help to explain.

 

[11bgrunt]

Since the 70s, motor loads and GFCIs have not worked well together. I may have taken a dedicated outlet to a single circuit with a 20A single to prevent these nuisance trips in new construction. I heard stories that when AFCI was introduced, the first service call in a new house and that AFCI breaker may have been replaced with a standard combination that worked.
I think this call is more than a compatibility issue..

 

[ptonsparky]

I have not done a lot of houses since I branched out to other types of work but I was called in to look at a new house that was having issues. They were all QO breakers and it was not improper wiring methods. Short of it, the QO supplier eventually replaced all the AFCI with a new, improved model, although QO tech support said the old were working as designed, and the EC no longer uses QO.

 

[ramsy]

When the four DF breakers trip at his house, he finds the pool breaker has tripped

Each house may have a different VFD or inverter appliance, device not FCC compliant, or arc-noise that resonates at xFCI, at a magnitude within proximity of multiple receivers. That is not unusual.

What seems novel, is utility excursions or radio EMP discriminating between xFCI models, unless RF harmonics of your POCO AMI PLC system can interfere with appliance harmonics?

 

[synchro]

... At random times a block of four QO120DF breakers, in the panel next to each vertically, trip simultaneously. Dishwasher, disposal, washing machine and refrigerator.
... Homeowner #1 has a pool with a double pole GFCI breaker for the pool. When the four DF breakers trip at his house, he finds the pool breaker has tripped.

Perhaps the appliances and pool pump have noise filtering and/or surge suppression that includes capacitors and MOVs shunted to the equipment ground. Then if there's a fast transient or surge, it might cause enough current to the ground to trip a breaker's GFCI function.

I don't know if it's in the scope of your responsibilties, but perhaps a power strip with surge suppression and filtering could be plugged into another circuit that has a GFCI or DF breaker. Preferably this breaker would be in the main panel to minimize the variables involved, but it could be in the subpanel. Then if this breaker trips along the the others that you mentioned, it would point to a fast transient or surge on the supply voltage as a cause of the tripping. Then you could go from there.