Please, see diagram and slap me if I am wrong ;)

[Balarizaaf]

Please see this diagram and make me sure I am ok with it..

View attachment projekt.pdf

 

[telectrix]

is this existing or new? if it's how you plan to install, then it's back to the drawing board. what's the earthing system?

- - - Updated - - -

if it's how you plan to install, then it's back to the drawing board. what's the earthing system?

- - - Updated - - -

start again

 

[D Skelton]

^^^^ What he said...

 

[Balarizaaf]

Its a replacement of existing one. CU is close to the meter, but only RCD and 100A isolator installed, then is going for first floor, to flat, where sub-CU installed. Its extreme small flat with very limited devices, 7 sockets and electric shower, small oven and hob. Will be 5 circuts. One lights (6A), one sockets closed circuit (20A), Kitchen appliance circuit (32A), shower (40A 6mm cable), Oven (40A 6mm cable) and 100A isolator switch. There is TNS-C.

 

[telectrix]

so what is the job you are doing? is it the flat CU only? those 15m tails should have fuse/MCB protection.

 

[Balarizaaf]

those 15m tails should have fuse/MCB protection.

I though it have be! Wasn't sure. Easy to do, I was more wondering of the 16mm2 cable (CU - sub-CU).

I am doing full re-wire.

 

[telectrix]

protect the 16mm tails with a 63A MCB. alongside the RCD.

 

[Octopus]

Is it a good idea to have a single up front RCD? 15m away from the CU. I don't, nor do I think its a good idea to ever have a single up front RCD.

 

[Engineer54]

Its a replacement of existing one. CU is close to the meter, but only RCD and 100A isolator installed, then is going for first floor, to flat, where sub-CU installed. Its extreme small flat with very limited devices, 7 sockets and electric shower, small oven and hob. Will be 5 circuts. One lights (6A), one sockets closed circuit (20A), Kitchen appliance circuit (32A), shower (40A 6mm cable), Oven (40A 6mm cable) and 100A isolator switch. There is TNS-C.

Reading this, ...you're a electrical trainee aren't you?? Do you think you're ready to undertake a full rewire, even if it is an extremely small flat??

 

[HandySparks]

Couple of thoughts:
Where is the MET?

Following on from Murdoch's point,
If the 15m run currently requires RCD protection, can you replace it with SWA and remove the up-front RCD, replacing it with RCDs or RCBOs in the flat CU?

 

[Balarizaaf]

Couple of thoughts:
Where is the MET?

Following on from Murdoch's point,
If the 15m run currently requires RCD protection, can you replace it with SWA and remove the up-front RCD, replacing it with RCDs or RCBOs in the flat CU?

I dont find anything disturbing about 16mm2 6181y tail. Please, correct me if I'm wrong...

@Handy - MET goes together with meter.

 

[Octopus]

I dont find anything disturbing about 16mm2 6181y tail. Please, correct me if I'm wrong...

@Handy - MET goes together with meter.

In which case you need to re-read post 8

 

[HandySparks]

I dont find anything disturbing about 16mm2 6181y tail. Please, correct me if I'm wrong...

@Handy - MET goes together with meter.

All I'm saying is that if you remove the RCD protection at the supply end and provide it at the flat CU instead, you need to avoid running the cable buried less than 50mm in a wall or use SWA or other suitable protection. See 522.6.101 of the current regs.

Are you planning to run the main protective bonding directly to the MET?

 

[mechelec]

Is it a good idea to have a single up front RCD? 15m away from the CU. I don't, nor do I think its a good idea to ever have a single up front RCD.

Really ??????? Never dealt with a TT earthing system then !!

 

[Octopus]

Really ??????? Never dealt with a TT earthing system then !!

yes. but most of these numptie posters don't work on TT and think they can use a single RCD, up front, to save money, which isn't a good idea.

 

[mechelec]

yes. but most of these numptie posters don't work on TT and think they can use a single RCD, up front, to save money, which isn't a good idea.

Good point.

 

[guest119]

The OP diagram shows a 100a isolator feering a 63 amp rcd., not rcbo
Therefor rcd can be provided with more current than it can safely handle.

Boydy

 

[mechelec]

The OP diagram shows a 100a isolator feering a 63 amp rcd., not rcbo
Therefor rcd can be provided with more current than it can safely handle.

Boydy

Why has the rating of his isolator got anything to do with how much current the RCD will see ? (As already stated in previous post RCD should be RCBO) As long as an isolator has a higher rating than it's supplying protective device (whose rating is not shown) it is irrelevant. It could be a 1000a isolator but if it was being supplied by a 60a fuse it would be fine ( overbuilt yes but electrically safe)
in industrial installations especially bus bar set ups very often the OCPD for the bus bars is a much higher ration of the switch fuses they supply.

 

[guest119]

Why has the rating of his isolator got anything to do with how much current the RCD will see ? (As already stated in previous post RCD should be RCBO) As long as an isolator has a higher rating than it's supplying protective device (whose rating is not shown) it is irrelevant. It could be a 1000a isolator but if it was being supplied by a 60a fuse it would be fine ( overbuilt yes but electrically safe)
in industrial installations especially bus bar set ups very often the OCPD for the bus bars is a much higher ration of the switch fuses they supply.

Because it looks like the op has fell into the trap of thinking a 63a rcd will provide overcurrent protection, for his 16mm tails thereafter.


Boydy