UK MCB Size for radial socket circuit.

[Toonjabba]

My shed is only 5 Meters from my house, i will run a SWA cable from existing consumer unit to a shed consumer unit which will have 3 circuits for Sockets,Light and a 7.5Kw shower unit all i need to know is will a 16 Amp MCB be sufficient for the socket Radial circuit for 4 Double sockets

 

[telectrix]

Thanks everyone for your comments I will take on board everything that has been said. I do have 17th edition cert and part p but was done a while ago and not had much experience. I just wanted to make sure it’s safe. I will be using 6mm SWA from house to shed then 3 separate circuits for lights sockets and 3 kw water heater. What MCB would you suggest using in the house CU.

40A MCB, assuming SWA is installed ref' method C, clipped direct with no insulation preventing heat dissipation.

 

[brianmoooore]

It would be preferable (to get better discrimination), to feed from a switch fuse at the house end, rather than a MCB.

 

[Toonjabba]

40A MCB, assuming SWA is installed ref' method C, clipped direct with no insulation preventing heat dissipation.

Thank you.

 

[pc1966]

It would be preferable (to get better discrimination), to feed from a switch fuse at the house end, rather than a MCB.

It would do.

However, I would suggest fitting at least one emergency style light (part of strip lights probably) in case power fails and not enough window light, as that helps mitigate the risks from power loss for any reason, not just poor selectivity on a fault. Might be easier and cheaper than the effort to split tails and insert a fused-switch for something of the order of 40A.

 

[Toonjabba]

Could someone please suggest where I can get a good priced 6-7 kw shower

 

[Mike Johnson]

I'v read through the thread and did not see any mention of RCD protection, IMO the CU in the shed should at least be supplied by an RCD from the main CU.

 

[DPG]

I'v read through the thread and did not see any mention of RCD protection, IMO the CU in the shed should at least be supplied by an RCD from the main CU.

Fair point. Although the SWA would be better fed from an MCB in the main board and then an RCD in the remote consumer unit?

 

[Mike Johnson]

Only if the MCB in the CU is already RCD protected. IMO

 

[DPG]

Only if the MCB in the CU is already RCD protected. IMO

Will the SWA need RCD protection in this case? I may need to re-read the thread.

 

[Deleted account]

I’m a little confused, actually a lot confused. Are we talking about the size of the final circuits or the size of SWA supplying the final circuits.

6mm was mentioned for a 7 kw shower. Fine for the final circuit, but I think the SWA should be higher considering the radial socket circuit that is being fitted.

as mentioned a heater, kettle hair dryer etc may and probably will be used on this radial.

so I’d say at least 10 mm for the SWA.

 

[Markyd]

A lot of questions for someone who is qualified

 

[Taylortwocities]

A lot of questions for someone who is qualified

not really qualified though, is he? Part P (whatever that is) and 17th edition just proves you can pass a couple of multiple guess papers. Is doesn’t touch on circuit design, or testing.
Think the OP is out of his depth on this, I wouldn’t want to send my dog there.

 

[suffolkspark]

A 7.5kw shower is probably gonna be rubbish in winter if you want decent flow to get in the furr and no shivery dogs? I'd say you want a decent supply out there, 63A or even 80A switch fuse at origin, appropriately sized swa (10mm 3core+ depending on upfront fuse size) and a small rcbo board out there, no point undersizing things to find out it's either gonna not be fit for purpose in use or keep tripping when you put a heater on if you size it tight and put an mcb upfront. You need to notify new circuits anyway so why not just get a spark in and have an honest chat about helping them?

 

[Toonjabba]

not really qualified though, is he? Part P (whatever that is) and 17th edition just proves you can pass a couple of multiple guess papers. Is doesn’t touch on circuit design, or testing.
Think the OP is out of his depth on this, I wouldn’t want to send my dog there.

I only asked 2 questions if you read all the way through is hadn’t done anything for a while so wanted to double check and it wasn’t a couple of multiple guess questions. Have you done the exam ? And I don’t think we would want to have your dog if it’s as rude as you

 

[pirate]

One day, when you are all very bored, I'll tell you the tale of fitting a 24V windlass on a boat, and then you will see what voltage drop is all about.
You have to get the "power" to the appliance...after that, who cares?
TBH, I was astonished at the power available, given the "tails" were tiny, but that's a whole different subject.