Arc Fault Breakers with a 120volt leg of a 208volt service?

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Tom Hedstrom

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Camden, Maine
Has anyone else had trouble with arc fault breakers on a 120volt leg of a 208volt service? When the load on the circuit gets up around 150 watts the arc fault breaker trips. This is a finished condo I walked in on today. My other guess is someone may have stolen the neutral off that circuit for something else, causing an imbalance. The only symptom I can find, other than the tripping breaker, is on the three way switching for that circuit I get 60-80volts to neutral and to ground on the runner that isn't being used at the moment. Has anyone seen/solved this?

thanks, Tom
 
AFCI's can be fussy but AFCI does not care if the 120V is coming from a Star or Delta or single phase source.

What are you using to load up the circuit?

60V on the runner, (traveler? You people in Maine do have some funny words) is probably just your meter reading phantom voltage.
 
As Dave stated the CB shouldn't care what the system is supplying the 120 volts. We just did 200 dorm rooms with AFCI breakers fed from a 480-208Y/120 volt transformer with no issues related to the supply.
 
First try to determine whether or not it is the ground current part of the AFCI breaker that is tripping.
If it seems to be proportional to the load current independent of the nature of that load, that is a very strong indication of a cross coupled neutral.
If you make sure that only that breaker is on, to avoid open neutral MWBC problems, lift the neutral at the breaker and still see low resistance from the circuit neutral to ground, that is the problem.
Next step is to figure out where.

Tapatalk!
 
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