Issues with Dual Function Breakers on 120/208 commercial panels

[electrofelon]

The original breakers were afci bolt on style breakers by code so we went with the dual function breakers not knowing that they would cause such and issue.
Your response about nuetral to ground voltage did get me thinking that may be the issue.

In my experience, by far the most common cause of AFCI tripping is poor wiring like neutrals from different circuits tied together or an EGC touching a neutral at a device. Some AFCI breakers have a ground fault component but it's often higher than the class A setting. Perhaps now that you changed to the dual function breakers you are at the class A 5 milliamp detection setting and it's now picking up some of those wiring errors. They can certainly be a bear to find. I would start with switch boxes, particularly ones with three ways where there might be multiple circuits with neutrals tied together.

 

[HertzGood85]

In my experience, by far the most common cause of AFCI tripping is poor wiring like neutrals from different circuits tied together or an EGC touching a neutral at a device. Some AFCI breakers have a ground fault component but it's often higher than the class A setting. Perhaps now that you changed to the dual function breakers you are at the class A 5 milliamp detection setting and it's now picking up some of those wiring errors. They can certainly be a bear to find. I would start with switch boxes, particularly ones with three ways where there might be multiple circuits with neutrals tied together.

Thanks for the reply and I like the way your thinking, that was also my initial response was to start checking along the home run. It is a pain to track down every box and inspect but it is a good start. I do not that there are no shared neutrals for the rooms that are affected because each return path comes back to the breaker and then the nuetral from each breaker is landed on the nuetral bus. In your experience could a lose ground wire cause a gfci to trip intermittently?

 

[electrofelon]

Thanks for the reply and I like the way your thinking, that was also my initial response was to start checking along the home run. It is a pain to track down every box and inspect but it is a good start. I do not that there are no shared neutrals for the rooms that are affected because each return path comes back to the breaker and then the nuetral from each breaker is landed on the nuetral bus. In your experience could a lose ground wire cause a gfci to trip intermittently?

Note it's not just shared neutrals / multi wire circuits that are a issue. A common issue is in boxes with multiple circuits, often switch boxes, where all the neutrals are tied together instead of being kept separate. What you could do is plug a big load like an electric heater into the problematic circuit and clamp the neutral conductors and see if it's all coming back on the neutral it's supposed to be on. Also check for continuity between neutral and EGC.

I don't see how a loose EGC would affect anything.

 

[tortuga]

HertzGood:

Did you say why is the breaker tripping? Arc fault or ground fault?

 

[kwired]

The GFCI feature of these breakers would be tripping pretty much immediately rather than intermittently if there is mix up of downstream neutral conductors. An AFCI only breaker may hold as long as there is no load or little enough load that there is no leakage current over 30mA. Square D AFCI's still have 30mA GFP AFAIK, but a dual function of course has the GFCI feature as well.

 

[tortuga]

DF breakers tell you why they trip, the first thing one should find out is what kind of fault you have. Arc fault or ground fault?

 

[HertzGood85]

Note it's not just shared neutrals / multi wire circuits that are a issue. A common issue is in boxes with multiple circuits, often switch boxes, where all the neutrals are tied together instead of being kept separate. What you could do is plug a big load like an electric heater into the problematic circuit and clamp the neutral conductors and see if it's all coming back on the neutral it's supposed to be on. Also check for continuity between neutral and EGC.

I don't see how a loose EGC would affect anyt

Okay I see what you are saying i did try to plug in some heavy duty carpet cleaning machines in the circuit and it would not trip the dual function breaker which i though was odd. But the breaker will trip randomly every 6 hours in an empty room with no load in a wing of the building with not custodial activity what so ever and when check the breaker it indicates that it was a ground fault...

 

[HertzGood85]

DF breakers tell you why they trip, the first thing one should find out is what kind of fault you have. Arc fault or ground fault?

Hey thanks for the reply. When checking the indication feature on the breaker it indicates that the breaker tripped due to ground fault every time. How does a breaker intermmittantly trip from a ground fauld one day and then go maybe 2 or 3 days and then trip again. Even in rooms that are empty with no load whatsoever?

 

[HertzGood85]

The GFCI feature of these breakers would be tripping pretty much immediately rather than intermittently if there is mix up of downstream neutral conductors. An AFCI only breaker may hold as long as there is no load or little enough load that there is no leakage current over 30mA. Square D AFCI's still have 30mA GFP AFAIK, but a dual function of course has the GFCI feature as well.

Hey thanks for the reply. Yeah that's thing when for the type of fault indication on the dual function breakers they register as having a ground fault every time. But why is it happening intermittently sometime hours sometimes days in between? These room have very minimum load because they are special care units for dementia patients and all lighting is 277 on a completely separate circuit.

 

[kwired]

It is the GFCI function of the breaker that is apparently tripping it, doesn't mean there is an actual ground fault occurring.

Some "noise" on the line even if unloaded causes GFCI's to trip, even if not originating from the protected portion of the circuit.

I once had a wall switch type occupancy sensor left over from a job, thought I would put it in the bathroom in my shop. Right away it kept causing a GFCI receptacle nearby (think on same circuit but said light was not on load side of the GFCI) to trip every time the light was on. Never did figure out why as I put regular switch back in right away figuring it don't like to play well with the GFCI. That has been like 15 years ago when I did that.

GFCI's don't like inductive kick back or other transients either. sometimes even when on the supply side of the circuit. Name brand ones are better at handling it but still sometimes trip when a big enough surge hits them, like during thunderstorms or even when POCO is having issues and maybe a circuit recloser is cycling or other switching activity causes transients on the line.

If all your effected GFCI's are tripping at same time maybe it would be easier to figure out some event that is occurring when they trip.

 

[hbiss]

How does a breaker intermittently trip from a ground fault one day and then go maybe 2 or 3 days and then trip again.

Simple. Anything that has surge suppression, and that's not just limited to outlet strips and the like because many devices have built-in SPDs, will randomly trip a GFCI. That's because SPDs clamp on the normal surges caused by motors turning on and off, switching transients from the POCO and a million other things that causes the voltage to momentarily exceed the clamp voltage. When they clamp, they conduct from hot to ground. Bingo!

With the increasing use of SPDs everywhere to protect sensitive solid state devices, GFCIs are becoming increasingly troublesome.

-Hal

 

[kwired]

Simple. Anything that has surge suppression, and that's not just limited to outlet strips and the like because many devices have built-in SPDs, will randomly trip a GFCI. That's because SPDs clamp on the normal surges caused by motors turning on and off, switching transients from the POCO and a million other things that causes the voltage to momentarily exceed the clamp voltage. When they clamp, they conduct from hot to ground. Bingo!

With the increasing use of SPDs everywhere to protect sensitive solid state devices, GFCIs are becoming increasingly troublesome.

-Hal

And if you already have say 3 mA of capacitive leakage just in the normal circuit it takes less of a surge to cause a trip than if your capacitive leakage were nearly non existent.

 

[HertzGood85]

It is the GFCI function of the breaker that is apparently tripping it, doesn't mean there is an actual ground fault occurring.

Some "noise" on the line even if unloaded causes GFCI's to trip, even if not originating from the protected portion of the circuit.

I once had a wall switch type occupancy sensor left over from a job, thought I would put it in the bathroom in my shop. Right away it kept causing a GFCI receptacle nearby (think on same circuit but said light was not on load side of the GFCI) to trip every time the light was on. Never did figure out why as I put regular switch back in right away figuring it don't like to play well with the GFCI. That has been like 15 years ago when I did that.

GFCI's don't like inductive kick back or other transients either. sometimes even when on the supply side of the circuit. Name brand ones are better at handling it but still sometimes trip when a big enough surge hits them, like during thunderstorms or even when POCO is having issues and maybe a circuit recloser is cycling or other switching activity causes transients on the line.

If all your effected GFCI's are tripping at same time maybe it would be easier to figure out some event that is occurring when they trip.Hm

Thats some good information and now that you mention it the i will never have just one trip because when i check the panel there will be a pattern of 3 or 4 all tripped on the same day and usually those that are tripped are fed off the either the A and B phase or the B and C phase only. Never all there during an event. Of course pinpointed exactly what time they tripped it difficult because i'm not here 24/7

 

[HertzGood85]

Simple. Anything that has surge suppression, and that's not just limited to outlet strips and the like because many devices have built-in SPDs, will randomly trip a GFCI. That's because SPDs clamp on the normal surges caused by motors turning on and off, switching transients from the POCO and a million other things that causes the voltage to momentarily exceed the clamp voltage. When they clamp, they conduct from hot to ground. Bingo!

With the increasing use of SPDs everywhere to protect sensitive solid state devices, GFCIs are becoming increasingly troublesome.

-Hal

Aww I see now, heres a question: could a completly separate circuit in the same conduit induce a voltage high enough through the insulation of wire to cause the gfci breaker to trip? if they were running a large 120 motor for say like a carpet cleaning machine?
thanks

 

[ptonsparky]

For some reason I thought the load side of GFCI protected circuits were supposed to be in separate raceways or cables from non protected. I may have to do some digging

 

[hillbilly1]

For some reason I thought the load side of GFCI protected circuits were supposed to be in separate raceways or cables from non protected. I may have to do some digging

Usually those type of places are wired in MC, but I don’t think the op has specified. Many years ago I troubleshot an assisted living complex when they first came out with arc faults. Panelboards were full of them. Each breaker put out enough heat from the breakers that the panel cover was almost too hot to touch. Siemens paid us to replace all of them, never heard anymore about it. A lot of wasted 12-3 mc on that job, the pm and foreman didn’t realize they required separate neutrals.

 

[Fordean]

Hello, we just recently installed over 120 breakers in a 12-year-old long-term skilled nursing facility. The breakers are the Square D QOB 20-amp 120-volt DF (Dual Function) style and the panels feeding them are 120/208-volt three phase. When we initially installed them a few of the breakers would randomly trip intermittently. But the ones that did would trip with hardly any loads on the circuits. These breakers feed the power to residential rooms. There are no shared neutrals on any of the circuits, no lighting or non-linear loads and no refrigeration or heating appliances. Short circuits and ground faults have been ruled out and tested for. Over the course of 4 months, we now had to revert 30 circuits back to the original afci breakers because the nuisance tripping has become too much of a hassle and we cannot figure out the issue. The remaining 90 dual function breakers continue to work fine and have not tripped.

I have read some of the other posts on here addressing this same issue and I'm starting to wonder if the issue is either due to too high of inductance in load wire back to breaker or could it be a power quality issue? I'm no engineer and I could really use some help on this one.

Thank you.

1 If a light bulb is screwed in not all the way Trip

2 Chandliers Had 20 bulbs 1 neutral and hot socket wired wrong at factory Trip

3 Breaker works with neutral Neutral to ground. Trip ex. Ground wire touching neutral screw I make guys screw unused neutral screw in some cases

4 Fancy lighting strips Even if u think keeping switch off to trouble shoot Its the neutral Not the hot

 

[tortuga]

IOn normal mode for the meter, I'm getting a reading of 0.7 mA leakage current on an empty (no load) room that is having issues and in a lived-in room with minimum loads I'm getting about 0.9 to 1 mA.

You have the best tool for the job as it can detect "complex, non-sinusoidal waveforms" so no matter how that 4-6ma is happing you should be able to see it with the meter.
I am wondering how are you taking the leakage current readings with the 368FC?
I'd replace the breaker with a standard 20A breaker (or a 30ma breaker if you have to leave it)
Set the fluke 368FC measure (log) the 'max' current 'imbalance'.

Then clamp both the hot and neutral

You should see an 'event' over 4ma.

I'd bring a standard plain old 20A breaker, a GFCI breaker as well as a 30ma 'GFPE' (class b) GFCI for that panel just to eliminate possibilities and study the issue.

 

[jim dungar]

You have the best tool for the job as it can detect "complex, non-sinusoidal waveforms" so no matter how that 4-6ma is happing you should be able to see it with the meter.
I am wondering how are you taking the leakage current readings with the 368FC?
I'd replace the breaker with a standard 20A breaker (or a 30ma breaker if you have to leave it)
Set the fluke 368FC measure (log) the 'max' current 'imbalance'.

Then clamp both the hot and neutral

Check the specs for your meter. Most of the clamp-on ones do not have the accuracy to differentiate fractions of mA.

 

[tortuga]

Check the specs for your meter. Most of the clamp-on ones do not have the accuracy to differentiate fractions of mA.

He has a 368FC, I believe thats the meter to have for this kinda issue: