Today, I personally went back to the house with the tripping problem and this is what I found.

I opened the panel and put a clamp meter on the circuit in question. It read .18 amps. I went in the house to the affected rooms and hit one switch, the breaker tripped. I reset it and tried another switch, tripped again. I did this with 6 different switches with the same result. After the 6th one I changed the breaker to a regular one. I could then turn every light on without tripping. After I turned everything on, I had a max reading of 11.62 amps on the meter(15 amp circuit).

Most of the switches on the circuit are Lutron Maestro, however even the standard single pole was tripping the breaker, but its fixture is a florescent.

What is causing the arc fault to trip? Nothing has a ground. Everything works fine with a standard breaker. Every switch caused a the circuit to open, so we can't limited the problem to one set of fixtures or switch. The same circuit was causing periodic tripping of a GFCI, but not constant like the arc fault. ?????????????????????

Could you have possibly have hooked the wrong neutral up to the AFCI?

The other thing you might do is install a standard circuit breaker and measure the load on both the hot and neutral with everything on to make sure they are the same.

Curt

AFCI have gfci built into them.The setting is higher ,30 MA as compared to 5 MA for a standard GFCI. You have a ground fault in this circuit. Why was it on a gfci before.

A ground fault would cause the breaker to trip right away unless there is a ground fault in every light fixture.

AFCI's do not have built in GFCI's but they do have GFP. The definition of a GFCI is a device intended for personal protection that functions to de-energize a circuit or portion thereof within and established period of time when a current to ground exceeds the values established for a class A device. Cutler-Hammer does make a combination AFCI/GFCI breaker.

Curt

That was the first thing I checked, it was right.

txsparky, The customer wanted 3 prong outlets, so we put them on a GFI. After several calls to reset the GFI, we replace all outlets with a GFi wired line only to get the lights off the GFI.

[Shrug]

Any chance there is a hidden splice somewhere and the neutral is being shared/spliced with another?

If you try measuring the load on the neutral and hot as I suggested above they should be equal. If not the neutral is probably tied in with a neutral of another circuit as stamcon suggested. Another test you could try would be to connect the hot to a standard breaker but leave the neutral disconnected then check to see if any of the lights or receptacles work. If they do your picking up a neutral from another circuit or the neutral from this circuit is grounded somewhere.

Curt

This makes me wonder if this is a K&T Job (no grounds apparently)

If it is K&T I would think you could have much trouble with the neutral being dedicated.

You could shut off all the circuits and lift all the neutrals off the bar and test for continuity between them, you may find that one neutral is tied into another somewhere in the house.

iwire,No K&T, just old romex (1950's-1960's)

I think you could be right that the circuit could be sharing a neutral. That makes the most sense. It will be easy to test for. Thanks for the ideas.