nuisance trips and arc fault breakers

[nosparks]

I am having a problem with an arc fault breaker that we have just installed. I am experiencing nuisance tripping. Could someone with a history of experience guide me along with some troubleshooting tips. This is a first for me and I am stumped. Thanks in advance for your help!

 

[stud696981]

Re: nuisance trips and arc fault breakers

The most common problem with AFCIs tripping I have found is where a neutral and a ground wire come in contact with each other, such as an outlet when it's pushed in the box after installation.

 

[davedottcom]

Re: nuisance trips and arc fault breakers

Try removing ALL loads from the circuit first, then one by one introduce each load, when it trips you know where the problem is.
What brand is it?

 

[gary]

Re: nuisance trips and arc fault breakers

Vacuum cleaners and surge protectors are known trouble makers.

 

[al hildenbrand]

Re: nuisance trips and arc fault breakers

nosparks,

You don't mention whether this is a new install or a change in an existing branch circuit.

If the AFCI has been added to a branch circuit, part or all of which is existing, another suspect is that the neutral is shared with another circuit.

 

[templdl]

Re: nuisance trips and arc fault breakers

I agree with stud696981.
What I do to identify the case is to remove all loads from the problem cirduit, turn off the breaker and remove the line, neutral and EGC from the breaker and ground bar. The check the resistance between the neutral and EGC. If it soesn't show open circuit then you have identified the problem. You'll have to go beck through each junction and outlet box to determine where the neutral and EGC have come into contact with one another. But it's more apt to be and outlet box where the EGC has folded forward enough to touch the neutrl terminal screm on the outlet.

 

[DBrambrink]

Re: nuisance trips and arc fault breakers

I have the same problem with an arc fault protector installed on an in-room air conditioning unit. Drove me nuts for awhile. Have since discovered than anytime the lights are dimmed in the living room, the arc fault unit trips. If the lights are set to full illumination, the arc fault unit doesn't trip. I think this fancy dimmer I bought is putting noise (harmonics) on the line, which the arc fault unit interprets as an arcing fault.

 

[templdl]

Re: nuisance trips and arc fault breakers

As has been related of this forum AFCIs do have GF of about 30ma sesitivity. With the type of load that you have, inductance such as motor loads, the line current and neutral my become unbalanced for an instant. The AFCI is looking for a balance and assumes that if the Line and Neutral current aren't the same there has to be a ground fault. The length of cable runs appeared to been a factor in nuisance tripping of GFCIs. Nuisance tripping was even more of a problem with those 50 and 60a GFCIs for spas. It's a pretty difficult task to have a 5ma sensitivity when the breaker's amp rating if 50 or 60a. I'm amazed that there isn't more nuisance tripping.
It would be interesting if you replace that AFCI breaker with a 5ma GFCI breaker to see if you get the same results. Even better if you had a 30ma GF equipment protecting breaker that would be close to the sensitivity of a AFCI.

 

[LarryFine]

Re: nuisance trips and arc fault breakers

Originally posted by templdl:
With the type of load that you have, inductance such as motor loads, the line current and neutral my become unbalanced for an instant.

There's no reason for current in one wire in a circuit to be different than that in the other, barring stray capacitance to earth.

The length of cable runs appeared to been a factor in nuisance tripping of GFCIs.

This is a possibility, since there can be capacitive coupling to earth, especially in underground wiring.

Nuisance tripping was even more of a problem with those 50 and 60a GFCIs for spas.

A big contribution to spa GFCI difficulties is the presence of water, especially in immersiobn heaters.

It's a pretty difficult task to have a 5ma sensitivity when the breaker's amp rating if 50 or 60a.

I don't believe there is a correlation between breaker rating and the GFCI sensing circuitry. 5ma to earth is the same on a 15a or 60a circuit.

 

[nosparks]

Re: nuisance trips and arc fault breakers

Thanks again all for your help I will take all of your suggestions into consideration. As far as loads go: we have two circuits for the bedrooms, lighting shared with smokes and one for receptacles.

 

[LarryFine]

Re: nuisance trips and arc fault breakers

Originally posted by nosparks:
Thanks again all for your help I will take all of your suggestions into consideration. As far as loads go: we have two circuits for the bedrooms, lighting shared with smokes and one for receptacles.

In the '02 and up NEC, they all must be protected; in '09, only the receptacles.

 

[templdl]

Re: nuisance trips and arc fault breakers

LarryFine, I would have to agree with you on the surface but re:

There's no reason for current in one wire in a circuit to be different than that in the other, barring stray capacitance to earth.

I've had enough inquiries as an application engineer that this is not all that unusual. Unless someone takes the time an invest the money to so and access each field application issue all we can do is assume that motors can cause GFCI nuisance tripping even though one would like to undestande that the L and N current should be the same.
Re:

I don't believe there is a correlation between breaker rating and the GFCI sensing circuitry. 5ma to earth is the same on a 15a or 60a circuit.

Yes you're right reguarding the 5ma being the same but a 15-20a load is a darned sight less that 50-60a. 50 and 60a GFCIs are more prone to nuisance trips because of their higher ampacity loads.