Bunched 2.5mm2 Swa 4core for garage supply.

[ban-all-sheds]

We are talking here of conductors in the 2.5mm² to 5mm² csa range.

i.e. with radii in the range 0.89mm to 1.26mm.

In copper conductors at 50Hz the skin depth is about 9mm.

So in the context of this discussion, i.e. in the context of the situation where you were looking for reasons for confusion there is no skin effect at 50Hz.

 

[Monkeh]

We are talking here of conductors in the 2.5mm² to 5mm² csa range.

i.e. with radii in the range 0.89mm to 1.26mm.

In copper conductors at 50Hz the skin depth is about 9mm.

So in the context of this discussion, i.e. in the context of the situation where you were looking for reasons for confusion there is no skin effect at 50Hz.

Always right, aren't we? Drop the attitude for once, and stop finding reasons to insult people.

 

[ban-all-sheds]

Will you show me the insult in that post, please?

 

[JohnW2]

It is simply just in a sub section called "Earthing, Supply types and Bonding". The tables are under the heading of "SWA earthing." Unfortunately I don't think that you can setup a URL with a comma, it's that long ago since it was setup!

Yes, you're right. Having done some detective work, it seems that I made the mistake (without realising) of clicking on one of the Tables. That results in the sub-section heading appearing at the top in a large, bold, font - which made me think it was the Table title. Apologies for the confusion.

Kind Regards, John

 

[JohnW2]

The title of the table refers to 'bonding'

No it doesn't.

No, it doesn't - see my reply to Spark123.

Kind Regards, John

 

[JohnW2]

John, I will be feeding the SWA via an appropriately rated RCBO from the house C.U. And installing it in to a Garage C.U. with a 63A RCD with a 16A and a 6A MCB's.

I think that most people would say that it's best not to have RCD functionality for the circuoit both in the house and in the garage. If there were a fault, either or both might trip. The most convenient (and, I presume, most usual) arrangement would be to have just an (appropriately rated) MCB (not RCBO) in the house and the RCD in the garage CU. That way you don't have to run back into the house if something in the garage trips the RCBO. The only conceivable reason for have RCBO and RCD is 'belt and braces', in case one fails to operate when it should.

As for load, I have no plans to fill every socket but I want the flexibility of numerous outlets. I understand diversity but also realise that if you have sockets then there's a good chance they will get filled!

You seem to be limiting yourself to a pretty modest load by having a 16A MCB in the garage for the sockets. With a meaty enough SWA feed, you could have a 32A sockets circuit.

I have to say that I'm inclined to agree with RF. Given the relatively short cable run you're talking about, it might make sense to just buy some 6mm SWA, even though your 2x2.5mm would probably do. Such cable on a 40A MCB in the house would allow you a 32A sockets circuit and a 6A lighting one in the garage.

I just need a robust supply that I won't be in need of upgrading any time soon. I spend my days overlaying cable or reconductoring Overhead Line which is inadequate for the load required from it due the increase in customer demands.

In which case I'm a little surprised that you've satisfied yourself with a 16A sockets circuyit in the garage - since that incluses virtually no future-proofing.

You also need to address the bonding issues I mentioned before. Are there any metal water or gas pipes entering (even if only to 'pass through') the garage and/or any metalwork of the garage structure which is in continuity with the earth?

Kind Regards, John

 

[Shorty73]

John, I will be feeding the SWA via an appropriately rated RCBO from the house C.U. And installing it in to a Garage C.U. with a 63A RCD with a 16A and a 6A MCB's.

I think that most people would say that it's best not to have RCD functionality for the circuoit both in the house and in the garage. If there were a fault, either or both might trip. The most convenient (and, I presume, most usual) arrangement would be to have just an (appropriately rated) MCB (not RCBO) in the house and the RCD in the garage CU. That way you don't have to run back into the house if something in the garage trips the RCBO. The only conceivable reason for have RCBO and RCD is 'belt and braces', in case one fails to operate when it should.

As for load, I have no plans to fill every socket but I want the flexibility of numerous outlets. I understand diversity but also realise that if you have sockets then there's a good chance they will get filled!

You seem to be limiting yourself to a pretty modest load by having a 16A MCB in the garage for the sockets. With a meaty enough SWA feed, you could have a 32A sockets circuit.

I have to say that I'm inclined to agree with RF. Given the relatively short cable run you're talking about, it might make sense to just buy some 6mm SWA, even though your 2x2.5mm would probably do. Such cable on a 40A MCB in the house would allow you a 32A sockets circuit and a 6A lighting one in the garage.

I just need a robust supply that I won't be in need of upgrading any time soon. I spend my days overlaying cable or reconductoring Overhead Line which is inadequate for the load required from it due the increase in customer demands.

In which case I'm a little surprised that you've satisfied yourself with a 16A sockets circuyit in the garage - since that incluses virtually no future-proofing.

You also need to address the bonding issues I mentioned before. Are there any metal water or gas pipes entering (even if only to 'pass through') the garage and/or any metalwork of the garage structure which is in continuity with the earth?

Kind Regards, John

Thanks John,

The only metal work present is the cross members for the roof. There are no pipes in the garage. These will be bonded to the fittings which will hang from them.

As for limiting myself to 16A you are correct. I will upgrade the Garage C.U to allow a 32a circuit. I shall run the feed in as 6mm and save the 4core for something else.

Many thanks

 

[bernardgreen]

I think the confusion is related to the fact that doubling cross sectional area does not double current carrying capacity

The reason double the cross section does not enable double the current is due to the fact that the surface area is not doubled so heat dissipation form the copper is not doubled

 

[ban-all-sheds]

Yes - CCC:circumference is far more linear than CCC:csa.

But in this case we aren't looking at a 5mm² conductors, it's 2 x 2.5mm², each one carrying 50% of the total current.