New Consumer Unit

[sherman0251]

Am i right in saying that when a new consumer unit is installed on a single phase supply there should be a double pole switch between incoming companies fuse and the Consumer Unit???

Was reading the 17th edition the other day and spotted this??

Regards Ian

 

[bongos]

There should be a main switch to isolate all live conductors but this can be in the CU itself, you do not require an additional isolator. Can't remember the reg off the top of my head though.

EDIT: 537.1.4

 

[sherman0251]

Well I thought it was a bit strange as the main switch is double pole and isolates all live conductors anyway. Only reason I could think was so that even the tails entering the Consumer Unit were isolated so the board was ALL dead (not just the circuits)

 

[RF Lighting]

You should have a single point of isolation, so a seperate main switch would be required if the tails were split in a henley block to feed two CUs etc, but not if you just have a standard single CU setup.

 

[Chri5]

But it's a 'nice' having one.

 

[RF Lighting]

It's an unnecessary additional point of failure IMO.

 

[Donkmeister]

It's an unnecessary additional point of failure IMO.

But a very nice thing to have if you want to cut all power to the CU for any reason... even with the main isolator set to "OFF" I don't think I'd want to poke around inside a CU.

 

[RF Lighting]

View media item 8401

 

[Donkmeister]

OK, so it's not suitable for use near flame throwers...

How the 'eck did that happen, anyway?

 

[ColJack]

the idiot fitting the CU thought that they were push fit connectors and didn't tighten the live..

seriously though, a loose live by the looks... gets hot and melts the switch and case..

 

[RF Lighting]

Loose connection or a faulty switch.

I borrowed the picture from this thread Clicky

 

[Lectrician]

It's an unnecessary additional point of failure IMO.

But a very nice thing to have if you want to cut all power to the CU for any reason... even with the main isolator set to "OFF" I don't think I'd want to poke around inside a CU.

What if "you want to cut all power off to the additional isolator"? Should be also install a third isolator too?

Addional isolators are pointless IMO.

 

[ColJack]

if it's PME then pulling th main fuse is isolation enough normally.. the neutral is at earth potential..

if you're that bothered then you could disconnect it after you pull the fuse....

 

[GaryMo]

You should have a single point of isolation, so a seperate main switch would be required if the tails were split in a henley block to feed two CUs etc, but not if you just have a standard single CU setup.

Would each CU and its associated equipment be regarded as an installation in its own rights?
If you see it that way then an upfront isolator isn't required.

I personally wouldn't fit one (read don't fit one) if I was installing a second CU by the side of the original CU but if for instance the second CU was again fed from a henley block and was situated on the other side of a wall, garage for example, then I think an upfront isolator would be a useful addition for the homeowner to isolate the supply in an emergency.

 

[sherman0251]

So I am getting the general idea that this additional isolator is not required! I thought it was an addition in the 17th edition that all board changes must have a isolator fitted!