AFCI's tripping blowing my mind

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dgrey

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Plymouth, MA
A little background....I recently installed a 400 a underground service to serve an existing dwelling and a large in law addition. Two meters with mains at socket . Parrallel conductors from pole to socket. Panel in main house was left as it was already served by a 4/0 SER from a meter main ( which was surplanted by a new 2 position socket). A 4/0 SER was run to inlaw MLO panel. Which leads to issue.... Problem is all AFCI and dual function AFCI/GFCI in new panel (inlaw) trip whenever something is plugged in or lights are turned on. The circuits hold until then. I investigated all the typical things, shared neutrals etc and find nothing. I cant honestly believe i would have a miswire in every circuit in the addition. My wife says I do dumb things but that would be a stretch even for me. In the meter socket the parrallel neutrals, SER neutrals, SER grounds and Earth ground all end up on the same buss at different points within the socket. I pulled all those off and had no continuity on in law SER Grd & Neut but did have continuity on older existing SER grd & neut. Found three grounds in existing panel on neutral bar moved to ground bar but that didnt change anything. Tried pulling grounds off buss in socket and just connecting them to earth ground and still nothing. I come to you, hat in hand, hoping that someone can point me in the right direction.
 
dgrey said:
little background....I recently installed a 400 a underground service to serve
existing dwelling and a large in law addition. Two meters with mains at socket . Parrallel conductors from pole to socket. Panel in main house was left as it was already served by a 4/0 SER from a meter main ( which was surplanted by a new 2 position socket). A 4/0 SER was run to inlaw MLO panel. Which leads to issue.... Problem is all AFCI and dual function AFCI/GFCI in new panel (inlaw) trip whenever something is plugged in or lights are turned on. The circuits hold until then. I investigated all the typical things, shared neutrals etc and find nothing. I cant honestly believe i would have a miswire in every circuit in the addition. My wife says I do dumb things but that would be a stretch even for me. In the meter socket the parrallel neutrals, SER neutrals, SER grounds and Earth ground all end up on the same buss at different points within the socket. I pulled all those off and had no continuity on in law SER Grd & Neut but did have continuity on older existing SER grd & neut. Found three grounds in existing panel on neutral bar moved to ground bar but that didnt change anything. Tried pulling grounds off buss in socket and just connecting them to earth ground and still nothing. I come to you, hat in hand, hoping that someone can point me in the right direction.
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Go back and check again for breaker neutral problem. They can be a PIA, but not like you have, unless it is screw up.

Make sure the neutal Is matched to the cb. What breakers?
 
Some thoughts:

1) Shared neutrals (you've eliminated this - no MWBC?)
2) Circuit neutrals terminated on bar instead of AFCI breakers (did you have a green helper helping you with this rewire?)
3) Neutrals crossed up in panel (e.g., Circuit #1 has neutral from circuit #15 on AFCI)
4) Receptacles pushed in so that the grounding wire is touching grounded terminals

Really reaching:
5) Bad batch of AFCI from factory
6) Nails in romex that went thru/bridged neutral/ground
 
I'm having a little trouble understanding what you did. Is the main house fed from the new 400 amp service? If it is, you said that "we left it as is", but you would need to isolate the neutrals from the grounds at that service.
 
I'm betting the neutrals are landed on the neutral bus and not the breakers.

This seems to be a common mistake. I had another electrician call me a few weeks ago wanting me to trouble shoot why all the AFCI's were tripping when any load was applied to the circuits in a new house he just wired. I asked him if he was sure the correct neutrals were connected to each breaker. He responded that Square D's instructions say not to connect neutrals to the breaker when using the plug-on neutral style breakers. I told him he was either misreading instructions or they were wrong. I told him I didn't really have time to help (jobs is about 2 hours round trip away) but to connect the neutrals to the breakers and let me know if that fixes the issue. I never heard back from him.
 
They are SQ d Plug on neutrals style. I put the neutral to the bar not the breakers cuz i thought that was the whole point of em. I will try putting them on the breaker. Thanks:D
 
dgrey said:
They are SQ d Plug on neutrals style. I put the neutral to the bar not the breakers cuz i thought that was the whole point of em. I will try putting them on the breaker. Thanks:D
Click to expand...

Always read the instructions and never assume :) The plug on neutral simply eliminates the pigtail; the breaker still needs to monitor neutral current.
 
mbrooke said:
Always read the instructions and never assume :) The plug on neutral simply eliminates the pigtail; the breaker still needs to monitor neutral current.
Click to expand...


Now that its been pointed out its so obvious, At one point I wondered out loud " Why would they still put the neutral screw on the breaker?" Fool :)
 
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