AFCI ISSUES

brian john

Senior Member
Location
Leesburg, VA
Lighting and residential are not my line of work, but I have been contacted to investigate numerous tripping AFCI at a residential property and looking into some insight from MH.

I received this from an on-site facility "engineer".

What are your thoughts?

. I put in another ticket for the breakers tripping, but I wanted to let you know that I may have found the root cause. After testing, the issue only occurs when the under cabinet LED lighting is turned on. Internet research indicates that some cheaper LED transformers induce interference into the electrical line, and can cause AFCI breakers to trip, even if the lighting is on another circuit than the one tripping. However, the tripping does not happen until a heavy load is applied, like a fridge compressor or vacuum. The two factors combined are what is triggers it to trip. Can you please pass that onto the contractors and see if they can investigate? Ideally, if this is confirmed to be the cause, the solution could be to replace the cabinet LED transformer with a better quality one. I will not be home much of today, so any updates should be via text or phone. Many thanks!
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
I put in another ticket for the breakers tripping, but I wanted to let you know that I may have found the root cause. After testing, the issue only occurs when the under cabinet LED lighting is turned on. Internet research indicates that some cheaper LED transformers induce interference into the electrical line, and can cause AFCI breakers to trip, even if the lighting is on another circuit than the one tripping. However, the tripping does not happen until a heavy load is applied, like a fridge compressor or vacuum. The two factors combined are what is triggers it to trip.
That behavior is consistent with my understanding of how AFCI breakers typically respond to applied electrical stimuli.
A common approach in an AFCi is to detect the presence of high frequency current through the breaker, which is presumably due to an arc. The load current waveform at the line frequency (e.g., 60 Hz) is also detected. AFCI's are often designed to trip if the amplitude of the high frequency signal is above a certain level, and it is also modulated in synchronism with the load current waveform (as it would be for an arc driven by the line voltage).
I believe other proprietary enhancements to this basic technique are also common.

In your case the AFCI breaker's bus may be being modulated by high frequency noise currents coming from the LED drivers as you described. Then a corresponding noise voltage would be developed on the breaker bus because the impedance of the service conductors, transformer, etc. would likely be quite a bit larger at high frequencies due to inductive reactance. An then the noise voltage on the bus would cause the load current to have a noise current component that can be measured by the AFCI, via Ohm's law.

The load current is also measured in an AFCI, and there's a trip curve of load current vs. time that must be exceeded (in addition to the presence of high frequency noise) in order for a trip to occur.

And so the presence of the two factors you mentioned (LED lighting and a heavy load) being needed before the AFCI trips makes perfect sense.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The threshold for declaring a series arc is about 8 amps, regardless of breaker size. The threshold for a parallel arc signature is more than the nominal breaker size and it serves only to trip promptly in a situation that would eventually cause a thermal trip if the current were continuous.

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Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Not surprised the electrons cause interference.

I was told by GE that an afci required about 4 amps before it could detect a fault. I am assuming the refrigerator is on that same circuit which would explain why it would only trip when the refrig or something else were on
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
We have likewise had this problem. Depending on the breaker manufacturer you might get some useful input from them (Siemens actually had a person assigned to AFCI tripping problems Siemens Technical Support: 1-800-333-7421)
In a couple of cases, we have had contractors add simple Ferrite ring noise suppresor cable clipls to the wiring and, as much as it sounds like snake oil, it solved the problem.
 

tesla six

Member
Location
Buffalo, NY
Occupation
Licensed Electrician
Based on personal experience I may initiate a case with the breaker manufacturer. In my case I worked with a Seimens support person on a couple different jobs to solve the problem originating with LED lighting as well as talking with the V.P. and an engineer at the lighting manufacturer to try solutions (one solutions was literally move the grounded conductor - neutral - of the problematic circuit to a different location of the same neutral bar it was on?!?!? it makes a difference) It took a few hours but we worked through it.

Also if you can get your hands on a Seimens Arc Detect meter (discontinued item), they can be handy, and point you in the right direction. Another trick is replace the AFCI with a another new AFCI, I had an appliance tripping the AFCI and went through all the connections of that dedicated circuit, tested the appliance with a witness and it would never trip for me. After several visits I brought a new AFCI and it solved the problem.
 

brian john

Senior Member
Location
Leesburg, VA
We have likewise had this problem. Depending on the breaker manufacturer you might get some useful input from them (Siemens actually had a person assigned to AFCI tripping problems Siemens Technical Support: 1-800-333-7421)
In a couple of cases, we have had contractors add simple Ferrite ring noise suppressor cable clipls to the wiring and, as much as it sounds like snake oil, it solved the problem.
Are there different designs of Ferrite Chokes for different frequencies or is there one choke fits most circumstances?
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
We have likewise had this problem. Depending on the breaker manufacturer you might get some useful input from them (Siemens actually had a person assigned to AFCI tripping problems Siemens Technical Support: 1-800-333-7421)
In a couple of cases, we have had contractors add simple Ferrite ring noise suppresor cable clipls to the wiring and, as much as it sounds like snake oil, it solved the problem.
I believe it would be appropriate to try a ferrite choke on the conductors connected to the source of interference, which was LED lighting in the OP's case. If you put the choke right after the AFCI breaker it might be effective in preventing false trips, but it might also attenuate noise from an arc on the branch circuit and potentially keep it from tripping in that situation as well.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I believe it would be appropriate to try a ferrite choke on the conductors connected to the source of interference, which was LED lighting in the OP's case. If you put the choke right after the AFCI breaker it might be effective in preventing false trips, but it might also attenuate noise from an arc on the branch circuit and potentially keep it from tripping in that situation as well.

Years ago when I had issues with ge afci I called them and they had ferrite chokes for the purpose. They did warn that the choke would not work on any circuit with dimmer switches.

It help in one instance but not another. We finally tried a different generation afci and that worked.

Might be worth seeing if the didn't screw up some wiring to those lights
 

Knuckle Dragger

Master Electrician Electrical Contractor 01752
Location
Marlborough, Massachusetts USA
Occupation
Electrical Contractor
Being pretty much ignorant of ferrite "ring noise suppressors" or "ferrite chokes". How would you choose the appropriate one in this LED light case and where would you install it?
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Being pretty much ignorant of ferrite "ring noise suppressors" or "ferrite chokes". How would you choose the appropriate one in this LED light case and where would you install it?
Trial and error. Don't you have a bin of ferrite cores of various sizes on your truck?

But before I went that route I would take the damn AFCI breaker out and run my truck over it.

-Hal
 
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