GFCI busbar

[electrics]

hi, do we need to have a separate GFCI busbar in subpanels? if so why? have a nice day, best regards...

 

[infinity]

Do you mean a separate Equipment Grounding Conductor (EGC) busbar? If that's what you mean the answer could be yes or no.

 

[electrics]

no no, just a bar which is coming after a GFCI (rcd ) and is connected to a main neutral bar and it feeds the neutrals of the outlets from here, namely it is intented to be a separate bar from main neutral bar and i cant see why

 

[Volta]

No, one common bar wouldn't work. Each individual GFCI device needs to have its load neutral isolated from all other neutrals or else it would be seen as a fault and the circuit would open.

 

[shepelec]

mis read the question never mind

 

[electrics]

hi again, excuse me but it sounds a bit weird for me ,when must we use such a separate busbar, is it true that whenever gfcı or rcd neutral conductor is through common neutral bar there occurs trip?

 

[Volta]

It should. Small GFCI breakers here in the states have a line side neutral wire, and a load side neutral termination. Since each device carries its own neutral point, no extra bar is needed to wire these.

 

[electrics]

so we say in short if we have some circuits which are not feeded through gfcı devices beside the ones which are feeded through them, so we need to separate the busbars as neutral and gfcı neutrals is it true?
By the way what u said at the last message means "in general small GFCI wont need busbars since they have neutral points on its own but this is just a supplemantary information as regards what u asked me" am i true, excuse me just wondering if it has any relation directly with the answer i seek, if it is so i thank u for ur extra infos, if not so excuse me i cant see the relation between what i ask and what u mean directly...

 

[shepelec]

I think what the op is referring too is, an RCD is a GFCI main in the UK. So yes you would need to have a seperate insulated neutral buss or it would trip.

The RCD monitors the neutral of the protected circuits. If a non-RCD neutral where connected to the RCD neutral it would be seen as a fault.

 

[electrics]

i cant see how neutral current will be divided nevertheless. Can u pls show it with drawings if possible=?

 

[shepelec]

Think of it this way. If the currents are not balanced between the hot and neutral the RCD will trip. If you were to connect a non-RCD neutral to the RCD neutral buss, it would show as an imbalance to the RCD, as you would show more current on the neutral than on the hot.

Protected and unprotected neutrals must be seperate for the RCD to work.

 

[electrics]

oh no, i dont mean crossover the neutrals, i mean how we get a tripping if we dont have separate rcd neutral ,i mean we have a panelboard neutral busbar and we connect all the neutrals (rcd and non-rcd ones) to this busbar and so how can there be a tripping because of the neutral current divide ? i want you pls tell me the gist of this dividing the busbars as main and rcd neutral busbars...

 

[George Stolz]

The concept behind a GFCI is simple: It takes two conductors to make a circuit, hot and neutral.

The GFCI looks at the current traveling along each conductor to be sure they are the same. If they are not the same, it trips and shuts off power to the circuit.

Regardless of where in a system the GFCI is placed, it will look at the downstream conductors for balance.

If power travels along the hot conductor, through the GFCI, through the load, and then has a pair of neutrals to return through, only half of the current that the GFCI expects to see will be on the neutral the GFCI is looking at. Therefore, it will trip; as it is assumed that such a condition entails a ground fault. Normally, when a GFCI sees 1A leaving on the hot, and 1/2A returning on the neutral, then the missing half amp would be returning to the source along a ground fault current path.

So, if you're protecting a whole feeder (not sure why you would) then you would need to ensure that all neutral current is returning to the neutral point of the GFCI supplying that feeder.

 

[shepelec]

This is a UK RCD, Like a GFCI main. In the UK almost all of the plugs are RCD protected.

You still need the 2nd neutral bar for the RCD neutrals. The neutral current does not know the difference. I assume you only have one RCD in the consumer unit.

 

[electrics]

if u have one neutral only in a panelboard so how can it be that a neutral will find any other way to the main (upstream and outside the panel busbar)neutral busbar? what u tell is i think is if u crossover the neutral across a rcd and non-rcd neutral busbars isnt it? what i cant get is if u have one neutral busbar how can it cause a tripping ?

 

[shepelec]

Because you can't balance the current going back to the RCD. Think of the way the RCD works. What goes out must come back. This is the only way the RCD can tell if it is fault current or normal current.

 

[electrics]

excuse me but i cant understand, pls tell me what u mean with one or two sentence, i mean with a generalisation something like a clause in a code, because i cant see what u mean, it is simple to understand that a rcd is a device which operates...... .part, but i cant see when do we need to use a separate rcd neutral busbar...

 

[shepelec]

Maybe I misunderstood you.

You are installing a new consumer board.

Is this board fed only by an RCD?

 

[electrics]

can we say about this something like this?
"if a rcd feeds some feeders and their neutrals neutral of any load which are fed through this rcd shouldnt be fed from any other neutral point than this rcd-connected neutral"_?

 

[shepelec]

can we say about this something like this?
"if a rcd feeds some feeders and their neutrals neutral of any load which are fed through this rcd shouldnt be fed from any other neutral point than this rcd-connected neutral"_?

YES!! That is correct