AFCI triping

[AKsparky1]

Follow me on this. Two boxes. one two gang and one four gang. The two gang has two 3-way,s and the circuit home run. The four gang has four 3-way switches. A traveler is connecting one 3-way from the two gang to one 3-way in the four gang via 12/3 NM-B and a switch leg is leaving the 3-way in the four gang to the light that uses 3 CFL's. Another cable carring the same circuit was brought from the two gang to the four gang to supply the other 3-ways. This duplex had to be wired this way because it is a premanufactured home consisting of four moduals. I know that in this case I must keep the grounded (white) conductors seperate in the four gang even though they are all originateing from the same circuit so that there is no parrallel path on the grounded conductors in the 12/3 and 12/2 in the four gang. At first glance you would think to tie all the gounded conductors together but this would be a code violation because you would have half the return current traveling on the white wire in the 12/3 traveler cable and the other half on the white wire in the 12/2 carrying the cicuit from the two gang to the four gang for the other swithches and you must have the grounded or neutral conductors for a circuit ran with its ungrounded conductors in the same cable or raceway. The problem is this circuit is served by an AFCI breaker and it trips unless you tie all the white wires together in the four gang. Now the strange is I seperated the grounded conductors in the first half of the duplex and did not have a problem. What are some of the other problems that cause an AFCI to trip other than an arc fault? No return current getting back to the breaker maybe......

 

[Ohms law]

All neutrals of the same circuit must be tied together, especially when on a AFCI breaker.

 

[Dennis Alwon]

Most brands of afci also have gfci built in that trip at ~40ma . You could have a ground fault situation. I am not sure why all the neutrals need to be joined together if they originate from the same circuit. Something must be crossed.

 

[Little Bill]

Follow me on this. Two boxes. one two gang and one four gang. The two gang has two 3-way,s and the circuit home run. The four gang has four 3-way switches. A traveler is connecting one 3-way from the two gang to one 3-way in the four gang via 12/3 NM-B and a switch leg is leaving the 3-way in the four gang to the light that uses 3 CFL's. Another cable carring the same circuit was brought from the two gang to the four gang to supply the other 3-ways. This duplex had to be wired this way because it is a premanufactured home consisting of four moduals. I know that in this case I must keep the grounded (white) conductors seperate in the four gang even though they are all originateing from the same circuit so that there is no parrallel path on the grounded conductors in the 12/3 and 12/2 in the four gang. At first glance you would think to tie all the gounded conductors together but this would be a code violation because you would have half the return current traveling on the white wire in the 12/3 traveler cable and the other half on the white wire in the 12/2 carrying the cicuit from the two gang to the four gang for the other swithches and you must have the grounded or neutral conductors for a circuit ran with its ungrounded conductors in the same cable or raceway. The problem is this circuit is served by an AFCI breaker and it trips unless you tie all the white wires together in the four gang. Now the strange is I seperated the grounded conductors in the first half of the duplex and did not have a problem. What are some of the other problems that cause an AFCI to trip other than an arc fault? No return current getting back to the breaker maybe......

Your AFCI also has GFCI protection in it (not the 5-6 MA, but around 30 MA). The GFCI is sensing an imbalance because of the way you have the neutrals run. That is what is tripping the AFCI.

Edit: Sorry Dennis, I left my reply in limbo too long before I hit the button!

 

[Ohms law]

Most brands of afci also have gfci built in that trip at ~40ma . You could have a ground fault situation. I am not sure why all the neutrals need to be joined together if they originate from the same circuit. Something must be crossed.

I should have said, only tie neutrals of the same circuit together. Also with combination type AFCI's, they monitor the neutral to ground. So if you have a ground touching a neutral terminal then the breaker should trip as well.