Basement CU

[plreardon]

Hi I'm adding a new CU tommy basement feed from my current CU.

Could someone help me with the size cable I need to connect the two and what fuse I need in my current board to feed the new one.

The new CU will be used to feed two lights and two sockets.

 

[westie101]

Change of story?

//www.diynot.com/forums/electrics/meter-tails.372226/

Just sayin

 

[riveralt]

Change of story?

Should be the same answer though!!!!

 

[EFLImpudence]

Surely those extra things can be connected to one or more of the existing circuits, therefore removing the need for an additional consumer unit.

 

[skotl]

Jeez. If you're just going to come back and ask the same question in the same forum and hope not to get flamed, could you not at least have gone and created a new username?

OK... I'll play along for a moment.

The size of cable that you need is.... (dons Ban-All-Sheds mask)...

... the size that your electrician recommends.


Seriously - it'll cost you ~£200 to get a qualified spark to do this for you - please at least ring one up and ask him for a price.

 

[securespark]

Ugger-bay Off-ay.

 

[ban-all-sheds]

Seriously - it'll cost you ~£200 to get a qualified spark to do this for you - please at least ring one up and ask him for a price.

Maybe he is too thick to understand how to use a phone?

He certainly provides lots of evidence here that this is the case.

 

[skotl]

Seriously - it'll cost you ~£200 to get a qualified spark to do this for you - please at least ring one up and ask him for a price.

Maybe he is too thick to understand how to use a phone?

He certainly provides lots of evidence here that this is the case.

Aaaarghh!! I'm turning into you

 

[PrenticeBoyofDerry]

The question looks a little different from previous post.

Hi I'm adding a new CU tommy basement feed from my current CU.

Could someone help me with the size cable I need to connect the two and what fuse I need in my current board to feed the new one.

The new CU will be used to feed two lights and two sockets.

If your intention is run a mini CU from the existing main CU, lights and sockets then:

*32A in main CU to mini CU with 20A or 16A for socket radial and 6A for lighting or
*20A in main CU to mini CU with 16A for sockets and 6A for lights

4mm cable should be sufficient for short distances.

Socket circuits would require RCD protection as will any cable buried less than 50mm within walls if not mechanically protected.
If cable for lighting circuit is surface mounted and for use in the cellar, my advise would be to exclude shared RCD protection of this circuit, so either use RCBO or MCB without RCD/RCCB.
This would then leave a lighting circuit, that can illuminate the cellar area where your CU is, this circuit would be free from nuisance trips from other circuits, therefore you can see to inspect the boards, if anything goes faulty elsewhere.
The advise to get a qualified electrician in from the start, that can install, notify, inspect, test and commission the installation is a very wise option to take, they may see things close up, that we cannot see from here.

 

[Aragorn84]

If your intention is run a mini CU from the existing main CU, lights and sockets then:

*32A in main CU to mini CU with 20A or 16A for socket radial and 6A for lighting or
*20A in main CU to mini CU with 16A for sockets and 6A for lights

From what i've read previously, regarding running garages from the main CU, its generally inadvisable due to insufficient discrimination between the "main" mcb, and the MCB's on the second CU?

Surely the above mentioned setup would have the same issues?

 

[JohnW2]

*32A in main CU to mini CU with 20A or 16A for socket radial and 6A for lighting or
*20A in main CU to mini CU with 16A for sockets and 6A for lights

From what i've read previously, regarding running garages from the main CU, its generally inadvisable due to insufficient discrimination between the "main" mcb, and the MCB's on the second CU? ... Surely the above mentioned setup would have the same issues?

Exactly the same issues - but if such a supply is to be obtained from a CU (rather than a separate submain), there's really no choice.

I personally don't think that this discrimination business is really much of a issue in the sort of situation we're talking about here. MCB trips are presumably going to be very rare events, and possibly having to reset two of them, in slightly different locations, 'once in a blue moon' is not really much of a hardship. It's different from the issue of, say, running a garage supply from an RCD-protected CU in the house - since a fault in the garage can then 'take out' some (or even all) of the house circuits.

Kind Regards, John

 

[PrenticeBoyofDerry]

From what i've read previously, regarding running garages from the main CU, its generally inadvisable due to insufficient discrimination between the "main" mcb, and the MCB's on the second CU?

Surely the above mentioned setup would have the same issues?

Inadvisable in what way, discrimination has been offered to the circuit, so in that way it is compliant.
What would you advise the OP do in this situation?

 

[JohnW2]

...discrimination has been offered to the circuit, so in that way it is compliant.

I guess it must just be me - but what does the above mean?

Kind Regards, John

 

[PrenticeBoyofDerry]

...discrimination has been offered to the circuit, so in that way it is compliant.

I guess it must just be me - but what does the above mean?

Kind Regards, John

WTF do you think it means, stop being an A.R.S.E

 

[Aragorn84]

From what i've read previously, regarding running garages from the main CU, its generally inadvisable due to insufficient discrimination between the "main" mcb, and the MCB's on the second CU?

Surely the above mentioned setup would have the same issues?

Inadvisable in what way, discrimination has been offered to the circuit, so in that way it is compliant.
What would you advise the OP do in this situation?

Well it the case of the garage, the situation described was a B40 in the house and a B32 in the garage. It was posed that a fault significant enough to trip the B32 in the garage, would also likely trip the B40 in the house. The danger then being the likelyhood of being plunged into darkness when the power-tool in your hands spinning at high speed has just gone faulty and tripped both the B32 and the B40. Or as john said, an earth fault taking out not only the whole garage supply, but half the house (or all of the house) as well.

I'd imagine the same situation would arise in the above configuration? Good design is supposed to minimise these effects?