Garage supply/RCBO Upstream

[John-SJW]

Fuse holders are still available for DIN rail mounting in CUs. One of these with appropriate fuse, swa cable, then mcbs or RCBOs in a garage CU. Selectivity solved.

https://www.bpx.co.uk/dbdocument/109463/DF101.pdf

Fuse Holders | Base Mount Fuse Holders | RS

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[pc1966]

Most of those DIN fuse holders are only 32A in the usual single-width spacing, also you need them to match the MCBs exactly for bus-bar location so suddenly you find them largely unusable in a domestic CU.

 

[John-SJW]

DIN rail fuse holders are available that match the size of mcb's, screw in and out of bus bars just like mcb's; Wylex, Schneider, Hager, for three. Not easy to get hold of, usually special order, many fuse rating sizes available, but they are there. They would make a much neater job as well with no separate adjacent switch. Cheaper than a separate switch/fuse holder near the house CU serving the garage, which are running at around £100, the last time I looked.

Wylex:

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[davesparks]

Fuse holders are still available for DIN rail mounting in CUs. One of these with appropriate fuse, swa cable, then mcbs or RCBOs in a garage CU. Selectivity solved.

https://www.bpx.co.uk/dbdocument/109463/DF101.pdf

Fuse Holders | Base Mount Fuse Holders | RS

Browse our extensive range of High-Quality Rail Mount, Panel Mount, Base Mount and Inline Fuse Holders. Order Today!

uk.rs-online.com

To be fitted in a CU they must be approved by the manufacturer of the CU for use in their CU, which effectively means all parts fitted in a CU need to be from the same manufacturer as the CU.
[automerge]1591094526[/automerge]

If someone drives a metal fork into an SWA, surely an RCD will protect the man?

Yes it will, but so will the armour of the cable. One key purpose of the armour is to ensure that any metal object penetrating the cable makes contact with earth first before making contact with a live conductor, this will cause the OCPD to operate.

This is why the armour must always be earthed whether it is used as the CPC or not.

 

[John-SJW]

The wider point is that supplies to out buildings will become more and more common as more people work from home with home offices being erected in gardens and garages being converted. When offices, they will need sockets, lights as minimum, however many will have ventilation, heating and maybe water heating to a small sink. It has to be done properly.

There is no defacto rule of thumb method of doing it at the moment. Many will be taken off rings from the rear of houses, when in terraced house situations, many using armoured cable from the house CU running down the side of the house. Others using catenary wire (yuk) to reach to the garden office.

However a prime aim must be, where it can be achieved, is to keep the overcurrent & fault protection contained within the outbuilding.

 

[radiohead]

The wider point is that supplies to out buildings will become more and more common as more people work from home with home offices being erected in gardens and garages being converted. When offices, they will need sockets, lights as minimum, however many will have ventilation, heating and maybe water heating to a small sink. It has to be done properly.

There is no defacto rule of thumb method of doing it at the moment. Many will be taken off rings from the rear of houses, when in terraced house situations, many using armoured cable from the house CU running down the side of the house. Others using catenary wire (yuk) to reach to the garden office.

However a prime aim must be, where it can be achieved, is to keep the overcurrent & fault protection contained within the outbuilding.

But really the same applies to all installations, they need to be done properly in accordance with Bs7671.
But judging by the number of questions relating to outbuildings on this forum there seems to be more confusion on this subject than any other. I suppose we should be thankfull that the 'exporting the earth' horror show hasn't unfolded as yet on this one.
Oh booger....I just mentioned it, hopefully I got away with it.

 

[John-SJW]

Yes, outbuilding's supply does cause confusion. It boils down to two:
1) Taking an outbuilding off a 32A ring. I have heard, and read, many variations of this. And many variations on the regs of how spurs can and cannot be used.
2) Taking the supply via a swa cable back to the house CU. Variations on this as well.

I see 1) as being the most used.

 

[pc1966]

Yes, outbuilding's supply does cause confusion. It boils down to two:
1) Taking an outbuilding off a 32A ring. I have heard, and read, many variations of this. And many variations on the regs of how spurs can and cannot be used.
2) Taking the supply via a swa cable back to the house CU. Variations on this as well.

You forgot to add:

3) Taking the supply via a swa cable back to a fused-switch

Also a lot comes down to the big variation in what sort of power is needed. For some it is simply lights and an occasional outdoor power tool, but others want the garage/outbuilding as a workshop (possibly meriting emergency lights for safety) or office (with heating and many sockets for PC supplies, etc), and other plan it as a stopping point to a hot-tub or similar.

So going 1-2-3 is improving the design, but also adding a bit of cost and complexity.

 

[John-SJW]

You forgot to add:

3) Taking the supply via a swa cable back to a fused-switch

That is really rolled into 1), taking it off a ring. OK it could be taken off a radial.