Question regarding 4 pole MCB

[44ALLAN]

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

Depends what you want to do.
Some have a 3 pole Isolator and Neutral bar separate.
Others have 4 pole RCD's..........there's a few permutations.

 

[i=p/u]

I thought main switch has to be 4 pole = isolate all conductors...

 

[44ALLAN]

I thought main switch has to be 4 pole = isolate all conductors...

Not necessarily.
Industrial boards you'll most likely find a solid bar for the earth and separate one for the neutral too with a 3 pole Isolator.

 

[Guest55]

I thought main switch has to be 4 pole = isolate all conductors...

only for a domestic do all poles need to be switched at the supply origin.

i never fit a 4 pole switch in commercial db , i've seen the mess it makes if the neutral contacts fail while installation is energised.

 

[martinh287]

I thought main switch has to be 4 pole = isolate all conductors...

only for a domestic do all poles need to be switched at the supply origin.

i never fit a 4 pole switch in commercial db , i've seen the mess it makes if the neutral contacts fail while installation is energised.

Was unaware of that on modern commercial db boards. I would prefer to be installing a isolated neutral to eliminate potential differences between neutral and earth particularly on a tn-s supply. I know on section boards with 60947-2's installed the neutral is not isolated but but at db level I would think it was a must have.

 

[johnboy6083]

I prefer 4 pole main switches too. I like to be able to isolate the whole board for testing and fault finding.

 

[i=p/u]

Just I put in quote for tp-n board and said 4 pole switch but the guy just quoted for 3 pole switch.

 

[johnboy6083]

Also the neutral links on MG boards are flimsy!

 

[BigAndyB]

So what's the trip time on the 4 pole ?
Are they adjustable like the ones agreco use in temp some supplies?

 

[martinh287]

Someone else might be able to debate a plus of having a 3 pole isolater instead of 4 pole but id be quoting for a four pole if I was you

 

[i=p/u]

And is this the incomer kit for the board ???

 

[Engineer54]

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.

Not quite sure i'm understanding you here. Are you saying the main switch/isolation for this DB is a Straight 4 pole RCD or 4 pole MCCB with earth leakage protection incorporated!! To be honest, i've never seen a commercial (or otherwise) 3 Phase DB with an RCD used as it's main switch!! Normally it'll be a straight isolator switch or an MCCB, (with or without earth leakage protection.)

 

[44ALLAN]

Not quite sure i'm understanding you here. Are you saying the main switch/isolation for this DB is a Straight 4 pole RCD or 4 pole MCCB with earth leakage protection incorporated!! To be honest, i've never seen a commercial (or otherwise) 3 Phase DB with an RCD used as it's main switch!! Normally it'll be a straight isolator switch or an MCCB, (with or without earth leakage protection.)

Like you said in an earlier post you can virtually make up any type of board you want nowadays with any configuration.
CEF own brand Proteus supply boards with rcd main incomers...........BX4R30 check them out.
All my 3 phase boards are fed from a local Switched Fused Isolator and over the years a few 'non-critical boards' have been left with a front end 30mA RCD covering all circuits..........eg the welding bay with one guy working in it with a few plugs and a radio dotted around the place
Never had a trip in 20 year so can't see the point in RCBO'ing the separate circuits to be honest.

 

[Engineer54]

Like you said in an earlier post you can virtually make up any type of board you want nowadays with any configuration.
CEF own brand Proteus supply boards with rcd main incomers...........BX4R30 check them out.
All my 3 phase boards are fed from a local Switched Fused Isolator and over the years a few 'non-critical boards' have been left with a front end 30mA RCD covering all circuits..........eg the welding bay with one guy working in it with a few plugs and a radio dotted around the place
Never had a trip in 20 year so can't see the point in RCBO'ing the separate circuits to be honest.

Didn't say DB's Don't come in this configuration, i said that i've never seen one!! lol!! Must be tiny welder if a 30mA RCD holds in, either that or it's shot!! I wouldn't have had a welder on an RCD in the first place, especially a 30mA unit lol!!

 

[44ALLAN]

Didn't say DB's Don't come in this configuration, i said that i've never seen one!! lol!! Must be tiny welder if a 30mA RCD holds in, either that or it's shot!! I wouldn't have had a welder on an RCD in the first place, especially a 30mA unit lol!!

Why would it be shot?
It's tested on a regular basis the same as all my equipment!!!.....seems you can't resist having a dig at folk mate !!