Issues with Dual Function Breakers on 120/208 commercial panels

[kwired]

That should have been EGC (Equipment Grounding Conductor)
For example (a poor mans tester) I put a 30k 3watt resistor in a cord cap wired hot to equipment ground, that pulls .004 amps @ 120V, just below the level a GFCl should trip.
If the GFCI trips at that level I say its defective and return it.
Or put two in series for a .002 Amp load (2ma).
With that nice fluke tester and standard test conditions I dont know how the manufacturer could stand behind their product and say it works.

If you added said test ground leakage to a circuit that already had 3mA of capacitive leakage you just exceeded GFCI trip threshold even though nothing was technically wrong with anything.

Same thing can happen with a circuit that has same 3mA of capacitive leakage and you then plug in some item that has 4 mA of leakage even though it won't trip when plugged in someplace else that doesn't have the 3 mA of leakage in the circuit already.

And we do have problems with items not being GFCI compatible these days, though the biggest common offenders which are variable electronic speed controlled motor driven loads don't seem to be mentioned in OP.

 

[kwired]

I had not figured out what turning on the filter on the meter meant until you just explained it, that's a good idea. What would you say a different reading would indicate through this higher frequency filter? On 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.

Also, I did do a check on that, and I would say 90 percent of the breakers I replaced were on the B and C phase in the panels. These panels are all in separate buildings and are fed off the load side of a step down 480 transformer but of course all power in the facility comes from main 2000-amp utility bus.

Do you have HVAC loads that is driven by a VFD? Though if they are on 480 volt side they likely won't impact the 208 side of transformer all that much. But you may want to analyze wave forms and make sure there is no high frequency harmonics causing troubles in the supply lines.

 

[ptonsparky]

Square D specifically states that circuit lengths of over 250ft can cause nuisance tripping of their GFCIs.

What is the maximum total length of load wire that can be used with a QO-GFI or QO-EPD circuit breaker? | Schneider Electric USA

Wouldn’t the circuit length be 2 times 125 for a total of 250?

 

[HertzGood85]

If you added said test ground leakage to a circuit that already had 3mA of capacitive leakage you just exceeded GFCI trip threshold even though nothing was technically wrong with anything.

Same thing can happen with a circuit that has same 3mA of capacitive leakage and you then plug in some item that has 4 mA of leakage even though it won't trip when plugged in someplace else that doesn't have the 3 mA of leakage in the circuit already.

And we do have problems with items not being GFCI compatible these days, though the biggest common offenders which are variable electronic speed controlled motor driven loads don't seem to be mentioned in OP.

Thats a good point if but these rooms have hardly any loads on them and I am only picking up .9 mA to 1 mA of leakage current on the breaker circuits that are having that issue. Yes all our HVAC equipment are running on the 480 side.

 

[HertzGood85]

Do you have HVAC loads that is driven by a VFD? Though if they are on 480 volt side they likely won't impact the 208 side of transformer all that much. But you may want to analyze wave forms and make sure there is no high frequency harmonics causing troubles in the supply lines.

Almost all of our HVAC motors are VFD driven but yes they are on the 480 side so I have been wondering how I would go about measuring for high frequency harmonics from motor start ups. We do have a fluke 435 II power analyzer on site. Thank you.

 

[HertzGood85]

Wouldn’t the circuit length be 2 times 125 for a total of 250?

Thats an excellent question and I've never thought of it that way, is that how the total length is calculated for max length on a 120 volt circuit?
I always figured the line and neutral each as one half the circuit needed to complete an entire run. But if your right I could well be over 250 feet in some rooms. But even though some of the problem circuits are less than 50 feet away.

 

[mtnelect]

Is this all-new wiring or are you still using some of the existing wiring ? If so, some of the grounded wiring might be crossed.

 

[HertzGood85]

Is this all-new wiring or are you still using some of the existing wiring ? If so, some of the grounded wiring might be crossed.

This is all existing wiring that was installed 12 years ago so its not in terrible shape. What do you mean by the grounding wires being crossed?

 

[mtnelect]

This is all existing wiring that was installed 12 years ago so its not in terrible shape. What do you mean by the grounding wires being crossed?

 

[tortuga]

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.

Did you say why is the breaker tripping? Arc fault or ground fault?
Are these the breakers without the diagnostic LED's and the diagnostic procedure is something like you hold the test button while the breaker is off then turn it on (while still holding test), then if it trips instantly its a ground fault or if there is a few second delay its an arc fault or something like that? I hate it when they dont just have an LED on there.

If you added said test ground leakage to a circuit that already had 3mA of capacitive leakage you just exceeded GFCI trip threshold even though nothing was technically wrong with anything.

Yeah good point, disconnect the branch circuit and install the resistor on some leads in the panel, or remove the breaker and test it at another location that has known good 208/120.

If the old AFCI breakers work:

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.

Try swapping the AFCI with just a plain GFCI breaker, or better yet try a QOB120EPD 30ma class B GFCI breaker on one of the problem circuits, then measure the leakage current over a few days with a data logger. It it trips a class B GFCI then you know you got a problem.

 

[tortuga]

Here is a 30k 2watt resistor

https://www.digikey.com/en/products/detail/yageo/RSF200JB-73-30K/18364

I'd solder it up to a nice loop of THHN at your shop and cover it with heat shrink.
Then wire it from the line terminal on the breaker to equipment ground bar and see if your new meter reads about 4ma.
A correctly calibrated GFCI breaker should never trip.

 

[synchro]

I have not tried that. If an unwired breaker doesn't trip that would indicate that breakers is bad correct?

If an unwired breaker trips it could indicate a bad breaker, or at least one that is more sensitive to voltage spikes on the panel bus or other power quality issues.
Does public safety personel with two way radios ever enter the buildings?

 

[electrofelon]

Why were the DF breakers installed? What was there before?

I would say most likely the breakers are just doing their job and it's a problem with the wiring, most likely a N-G bond. I'm really not sure why when an AFCI trips nearly everyone jumps to it being a bad breaker or some kind of inverse deractance from unilateral phase detractors causing the breaker to trip when it shouldn't.

 

[hbiss]

Why were the DF breakers installed?

My question also. Is there some requirement that AFCI/GFCI breakers be installed for all circuits in this commercial facility? Or was it some misguided management decision? Doing this can only lead to problems. AFCIs are useless and we are finding that GFCIs don't play well with newer equipment. Likely you will never find a solution that will make them work, and that causes more problems than they thought they would prevent. Power outages in patient rooms should never be tolerated.

Go back to regular breakers and install GFCI receptacles where required by the NEC.

-Hal

 

[HertzGood85]

My question also. Is there some requirement that AFCI/GFCI breakers be installed for all circuits in this commercial facility? Or was it some misguided management decision? Doing this can only lead to problems. AFCIs are useless and we are finding that GFCIs don't play well with newer equipment. Likely you will never find a solution that will make them work, and that causes more problems than they thought they would prevent. Power outages in patient rooms should never be tolerated.

Go back to regular breakers and install GFCI receptacles where required by the NEC.

-Hal

Hey Hal, the decision was made to go with these breakers on the forethought that it would save time with our required monthly testing of gfci's in our resident's room. Because we are a medical facility we have yearly inspections by several different agencies, and they require seeing paperwork indicating that we tested manually tested the gfci push button in each patient's room and logged it. The idea was to protect the entire room with the gfci and have all manual test buttons at one location via the panel. This has proven to be a major issue as seen. The 120 we installed were just a test run and there are over 400 more to install because procurement decided it best to just buy them all in bulk. At this point im ready to go back to the regular AFCI's but it's not decision at the moment. If i can find some reasoning, then maybe i can convince them but for now im faced with finding the reason why 30 out of the 120 have tripped and others have had no problem.

thanks for the post i feel the same as you about it

 

[HertzGood85]

If an unwired breaker trips it could indicate a bad breaker, or at least one that is more sensitive to voltage spikes on the panel bus or other power quality issues.
Does public safety personel with two way radios ever enter the buildings?

Thats an interesting question because just about all personnel here have hi band radios, its how we operate. Could that affect the breakers in some negative radio? thanks

 

[HertzGood85]

Why were the DF breakers installed? What was there before?

I would say most likely the breakers are just doing their job and it's a problem with the wiring, most likely a N-G bond. I'm really not sure why when an AFCI trips nearly everyone jumps to it being a bad breaker or some kind of inverse deractance from unilateral phase detractors causing the breaker to trip when it shouldn't.

Those were my initial thoughts exactly especially when first troubleshooting. I am wondering if a loose wire connection could be causing this issue since the contractor who installed used stab in connection almost everywhere which i know i notorious for failing.

 

[HertzGood85]

Thats an interesting idea and thank you for the code submittal information. I read it but i still don't understand what they mean by crossed ecg? is that an ecg that is carrying voltage potential like in lost neutral system? thanks

 

[electrofelon]

Those were my initial thoughts exactly especially when first troubleshooting. I am wondering if a loose wire connection could be causing this issue since the contractor who installed used stab in connection almost everywhere which i know i notorious for failing.

So I'm still not clear, were there afci breakers in there before? Or were they just regular breakers? If the latter, why didn't you just use GFCI breakers instead of dual function breakers?

 

[HertzGood85]

So I'm still not clear, were there afci breakers in there before? Or were they just regular breakers? If the latter, why didn't you just use GFCI breakers instead of dual function breakers?

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.