Power to the Shed

 

DISCLAIMER: I am not an electrician, Many years ago I passed the 16th Edition after a 3 year evening course. Now the regs are on 18th Edition with a couple of amendments. They seem to change, correct and contradict over time. What was once safe practice is now deemed dangerous and visa-versa.

So, I want to have power in my shed. It used to be that I would do that as a DIY task and notify nobody. Then Part P came into force and banned that practice. I did the electrical course and still wasn't Part P.

Now I just do as much DIY as I can, then get a qualified electrician to complete or redo.

This time around it has been a lot harder as I am receiving conflicting information over what is the safe way to do this.

 It's no longer fun to do, and I am giving up early. Someone better informed than me needs to do the work. But this is a record of where I am.

I'll start with the contentious issue of earthing the shed. I have always just run SWA cable from the house to a new consumer unit in the shed and used that Earth. Previously none of my sheds had any outside metal bits you could touch so didn't need additional bonding.
Now, a lot of people say it should be a local TT arrangement, whereby I don't use the house earth. Instead it has an earth rod, maybe 2 meters long and bashed into the earth. But I don't get an explanation as to why they want to do that. So I am reluctant to do that.

The latest Special Locations book by the IEE says as far as I understand it that the earth from the house is the preferred way. The last paragraph does mention a TT system, but it is an alternative not a regulation

Some of this confusion may be around Electric Car Chargers, This is new technology. There is a chance you are charging your car, touching the car, when someone drills through the electric mains on the high street, taking out the Neutral. Because most supplies use a combined neutral and earth, all that voltage will go through the earth cable and you'll get a big shock. So it was a requirement to have an earth rod for the EV charger. Not the entire shed, just the charger.

This video from JW is great. It talks about the issues that you can create when mixing TT systems with TN systems.

The last couple of amendments to the 18th Edition have changed that requirement to include alternatives. Newer EV chargers now have their own voltage protection built in, avoiding the use of an earth rod.

Amendment 1 is discussed here:

Amendment 2 is discussed here:

I'm starting to get a bit lost now. Is TT in/out or additional ?

Anyway, back to my shed. I will be having something metal near it - an old Victorian style cast iron lamp post.

I have already set the plinth it is to stand on and run a cable ready for connection. I thought that was all good, but then thought does this need additional bonding ? There will be an earth to the brass bayonet lamp holder, which is screwed to the cast iron. Is that sufficient ? I don't know, so i've stopped work on that. Then I look at all the metal fencing I have, and the metal staircase - oh my god I have metal everywhere!

I will also say that I am planning on installing an EV charger at some point, but I would think any additional earthing that may be required would be done by the installers. But I would buy one that has voltage protection anyway.

In the shed I have fixed a small consumer unit.

The 10mm SWA is in place although I have not connected anything. Probably best at this stage that whoever is going to test it, should fit it.

The cable runs down and out the shed, under my plinth for the outside light.

Then along the fence it is fixed by cleats. As I was doing it I was thinking is this actually the right way of doing it.

I have drilled through the posts. What happens if I need to replace that fence. It then goes up a bit of wall.

and finally along the balcony to the house.

Again, I have stopped this task for now in case what I have done previously is wrong. The cable isn't long enough to go all the way to the house consumer unit. I was going to get some 10mm non-armored cable for the rest of the run. But I want the cable to get into the loft, rather than have an ouside connection to a box. 

At the house consumer unit end - well, I say house. It's actually a flat above a shop.

The main supply coming in below is 3-Phase. The shop has 1 phase, the flat has 1 phase and there is 1 spare. Probably a bad way of doing that. 

A couple of pics of that supply. Originally it look like this.

For some reason only 1 of the 3 fuses was used. Look how small the supply earth cable is.

I then had this upgraded to 100 watts and it looks like this.

 Somehow, not sure if it was the upgrade, or the cables were always wrong, but the live and neutral for the shop supply were reversed. That was considered an emergency and UK Power Networks were straight out to fix it. 

Back to the flat, I want to replace the consumer unit with one that has surge protection and convert the mcbs to rcbos for circuits that need it, which is all of them them except the supply to the shed and the supply to the downstairs utility room. I believe these should not be rcd protected at source, but at the consumer units in their locations.

I intended to also do that myself, but I may be getting into illegal territory there, so stopped that task as well. 

The current one looks like this:

That is the end of my story in attempting to get power to my shed. So near but so far.

Now the search begins for an Electrician to take over - or in the worst case, re-do!

PS - Also needs doing.

• Reconnect the Smoke Alarm. I had to dismantle a lot of it for the Plasterers.
• Fix light in Kitchen - or convert both lights to LED bulbs.