Question regarding 4 pole MCB

[ozj999]

Hi all,

63A 4 pole MCB is it mean that it will trip when the total current of the 3 phase supply exceed 63A? Or it will only trip when only any of the phase current exceed 63A?

 

[Knobhead]

Any of the poles.

 

[Engineer54]

Each pole is rated at the rating shown on the device. So the MCB will trip when any one of the poles exceed that rating, subject of course to the normal time current curves of whichever type of MCB it is!!

 

[itselectric]

I've never seen a 4 pole MCB. Thats not to say there isn't any. I 'm curious as to the D.B. it would be compatible?

 

[44ALLAN]

I've never seen a 4 pole MCB. Thats not to say there isn't any. I 'm curious as to the D.B. it would be compatible?

Some of them fit direct onto the 3 phase solid busbars in the D/B ( instead of your normal 3 pole isolator) then a link cable is wired across onto the neutral link.

edit..........that's a 4pole Rcd I was on about misread your post.
Google 3phase and neutral mcb though and you'll see the types there are.

 

[itselectric]

Just googled it, as I said before I've not seen one. I have seen 4pole rcd's and mccb you live and learn.
When I googled the mcb the first one that came up was a Merlin Gerin. I've installed plenty of their boards before but not one that would take a 4 pole. If you let the wrong man loose with one of those on a standard merlin gerin board there could be some interesting repercussions

 

[44ALLAN]

Just googled it, as I said before I've not seen one. I have seen 4pole rcd's and mccb you live and learn.
When I googled the mcb the first one that came up was a Merlin Gerin. I've installed plenty of their boards before but not one that would take a 4 pole. If you let the wrong man loose with one of those on a standard merlin gerin board there could be some interesting repercussions

I'm guessing the main difference is the MCCB will have a higher breaking capacity than the MCB but they will both still open all 3 phases AND neutral when tripping.
Most of my bigger machines have MCCB as main switches/isoloators.

 

[itselectric]

The point I was trying to make was someone with not enough knowledge installing a 4 pole mcb into a standard db they would end up with a phase on the neutral pole

 

[Engineer54]

Some of them fit direct onto the 3 phase solid busbars in the D/B ( instead of your normal 3 pole isolator) then a link cable is wired across onto the neutral link.

edit..........that's a 4pole Rcd I was on about misread your post.
Google 3phase and neutral mcb though and you'll see the types there are.

MG (Schneider) DB's can be arranged to cater for just about any configuration you require, including TP+N compact bus bars of various descriptions.

On earlier projects, we've used such DB's specifically for areas where DP and vigi units and 4 pole breakers with 4 pole Vigi units were called for!! The 4 pole breakers with vigi units, works out to about 20cm in length or so!! ...lol!!

 

[Engineer54]

The point I was trying to make was someone with not enough knowledge installing a 4 pole mcb into a standard db they would end up with a phase on the neutral pole

I doubt very much if a DI would ever get to see a 4 pole MCB, let alone install one. Besides you would need to be an absolute fool to install one in a standard DB!! ...lol!!

 

[44ALLAN]

The point I was trying to make was someone with not enough knowledge installing a 4 pole mcb into a standard db they would end up with a phase on the neutral pole

No need to fit a 4 pole Mcb into a D/B though.
Mcb's will be fit onto the outgoing legs and normally just a 3 pole isolator to cover the board.
Must admit though I have a few boards covered by a 4pole Rcd...........one trip and the lots off lol

 

[Engineer54]

Something like a fail safe system them!! lol!! Not a very well planned/designed installation having a EL protection at the front end, with nothing downstream to discriminate with. Can be more trouble than they are worth in most cases!! lol!!

 

[martinh287]

Another four pole mcb could be a standard three pole 60898 mcb with shunt 26946 attached. This would allow the isolation of all line conductors under fault condition or with s vels unit attached to the shunt will operate as a rcbo

 

[44ALLAN]

Something like a fail safe system them!! lol!! Not a very well planned/designed installation having a EL protection at the front end, with nothing downstream to discriminate with. Can be more trouble than they are worth in most cases!! lol!!

I agree but, without tempting fate, I can't remember the last time an Rcd tripped ! ( maybe I should test them they might all be stuck eh!! ) lol
The 3 phase boards in question have them as their main switch and until I get any nuisance tripping their staying that way.

 

[i=p/u]

In tp-n boards is it not 4 pole mcb as main switch? Or isolator