GFCI's on 3 phase circuits

[farnorthsparky]

Just curious, when installing GFCI receps on a three phase circuit, does each phase need it's own neutral, since GFCI's operate due to an imbalance between hot and neutral?

 

[BullsnPyrs]

The nuetral can't be shared from the GFCI out to the end of the protected circuit.

 

[hurk27]

Just curious, when installing GFCI receps on a three phase circuit, does each phase need it's own neutral, since GFCI's operate due to an imbalance between hot and neutral?

The circuit feeding a GFCI receptacle can be a multi-wire circuit (shared neutral), but not the load side, if you use breakers, single pole GFCI breakers will need their own neutrals, but you can share a neutral with two pole.

 

[480sparky]

You can feed the GFCI recep with a MWBC, but you can't Line-Load protect any receps beyond the GFCI recep with it.... each circuit must have it's own grounded conductor.

 

[normbac]

You can feed the GFCI recep with a MWBC, but you can't Line-Load protect any receps beyond the GFCI recep with it.... each circuit must have it's own grounded conductor.

Could you explain that. Are you referring to three phase only. Is wiring a 12-3 to two sa circuits a violation?

 

[480sparky]

Could you explain that. Are you referring to three phase only. Is wiring a 12-3 to two sa circuits a violation?

A GFCI works by comparing the amount of current on the grounded (neutral) to the current on the ungrounded (hot). If they are more than 5ma different, the GFCI trips.

If you try to use GFCIs on a MWBC to protect 'downstream' receps, one of the GFCIs (or two, in the case of three phase) will trip because the 'hot' and 'neutral' will always be different.

You can feed three GFCI receps with a 3-phase MWBC, but you cannot use the MWBC to protect any 'downstream' receps.... you must use a separate grounded for each circuit.

 

[hurk27]

Could you explain that. Are you referring to three phase only. Is wiring a 12-3 to two sa circuits a violation?

All he is saying is you can use a MWBC up to a GFCI receptacle but not after it, load side has to have separate neutrals, and yes you can use a MWBC to feed SABC but you now have to have handle ties for the breaker's feeding it.

 

[480sparky]

All he is saying is you can use a MWBC up to a GFCI receptacle but not after it, load side has to have separate neutrals, and yes you can use a MWBC to feed SABC but you now have to have handle ties for the breaker's feeding it.

Or a two-/three-pole breaker.

 

[normbac]

So when I see two SA circuits in a kitchen with a 12-3 how is this working are the gfci not protecting correctly. TIA

 

[480sparky]

This:

will not work.



You either need to separate the neutrals after the GFCI receps:

Or install a 2-pole GFCI breaker:

Option #2 won't work on three-ph. as I don't think anyone makes a 3-pole GFCI breaker.

 

[normbac]

Thanks I misunderstood what you were saying

 

[480sparky]

Thanks I misunderstood what you were saying

Pictures are worth a thousand bucks. I accept cash, PayPal and check.

 

[normbac]

Pictures are worth a thousand bucks. I accept cash, PayPal and check.

That's why I love mike holts books.