Garden Sheds

[fosterweb]

Hi members, we recently moved a new house which has 2 sheds in the garden, both of which have an electricity supply. Set-up is the feed comes directly from the trip-box to the first shed. In the first shed is a junction box, with 3 wires. The feed, the first shed plug and the feed to the next shed. The next shed is the same with jsut a plug inside.

The second shed however is old and very damp, so I have switched off the main feed to the sheds. Now I opened the junction box, hoping to see what I am used to but alas, it was a little more complicated than my knowledge so far stretches.

All I want to do is disconnect the feed to the second shed.

The wire that feeds the first shed, and then the wire from the first shed that feeds the second shed is a thick black wire. These two thick wires I think, are twin and earth with an earth amoured feature.

Like this http://www.alertelectrical.com/upload/products/764cable6943xlh.jpg

Now when opening the junction box I discovered two wires, which I think are the earth armoured connections to not be connected. I have a fairly good idea about what its all about but with electricity its much better to be safe than sorry and ask some experts!

Here is a shot of the set-up, I apologise for the poor lighting but I did not want to connect the supply with the damp shed and with the junction box opened.

Shed Junction:

The top of the junction box leads to the 1st shed plugs with a standard twin and earth core. The left leads to the second shed (what I want to remove) and the bottom is the feed from the trip box.

Now you may be thinking, just remove the second shed feed, why are you asking this, but I have plans to purchase a new shed, which I will eventually want to wire back up using the same set-up displayed now.

Thanks in advance, any advice greatly appreciated!

 

[securespark]

Ok.

First of all, is the circuit up to the job? Is it RCD-protected?

How long is the circuit from main CU to first shed?

How big is the cable, and how big is the breaker feeding it?

See, I ask these questions because you want to use the supply to the first shed and reinstate the supply to the 2nd, so I want to be sure it is adequate.

Second, what is that blue conductor connected to the yellow, and the other blues? I guess the yellow is the cpc?

Third, the wires not connected: are they silver and not coated in plastic?

If my diplopia-ravaged eyesight serves me correctly, is that a silver wire attached to the yellow?

In this case, the armour seems to have been cobbled together ith the cpc.

The SWA cable should be made off correctly into (preferably) a galv. adaptable box with proper glands & banjo's making good earth connections between all cables.

There needs to be a bit of tickling up to put things right.

 

[fosterweb]

It is RCD protected yes. It is not too far away, about 10-20 metres. I am guessing that the blue with the yellows are the earth so the earth core and the earth armoured are together. It that ok? I may have knocked the blues out as I pulled the terminal out. Not too sure how big the wire is, quite bulky

 

[breezer]

quite bulky

two rolls of "quite bulky" cable please

sorry i couldn't help that

 

[fosterweb]

Haha I will find out in the morning if it is not poosible to assess with that info

And I forgot to put is a B16 MCB

 

[ricicle]

Unless those are GIANT connectors those cores look a bit small

 

[JohnD]

It would be useful to have a look in the consumer unit ("trip box") where the circuit originates (we'd like a photo, too, otherwise please describe it and say what brand and colour). You particularly need to identify what colour of the SWA is connected to what, at source so that you can maintain correct polarity and continuous earthing.

You would hope to find that the steel armour is connected to Earth at source, but from the look of the junction box you showed, I would not be surprised if it isn't. As Secure says, SWA (Steel Wire Armoured cable) is usually terminated in a steel box, with a brass gland that grips the steel armour and forms a strong mechanical and electrical joint with both armour and the steel box. This is not very easy to do without practice. It is not usually satisfactory terminated in a plastic box, and being heavy and stiff, it can bend or tear plastic enclosures. The steel box can be placed inside, out of the weather, so it does not rust much.

Also, can you say how deep the SWA is buried; or what it is attached to if not?

 

[fosterweb]

The SWA is not buried, it is suspended from the garage roof to the shed roof.

Here is our box etc:

Whole view

Shed switch

RCD

Now the wire from the shed runs out which is a twin and earth wire into a junction box which swaps the wire to the SWA wire which runs to the shed.

Standard Wire ---> SWA Wire

 

[securespark]

Looks like 2.5.

20m gives you a volt drop of 5.76.

Seeing as the breaker is off, can you remove the lid on that conduit box where the grey cable meets the black?

That'll give us an idea how the cores are connected.

 

[fosterweb]

Sure, as you may or may not be able to clearly see, the blue is connected to the box itself.

 

[fosterweb]

Edit just noticed, looks like 1 blue connected and another not...

 

[securespark]

What's that red (top right)?

And is that a black in with the yellow?

 

[fosterweb]

The red on the top right is the live feed from the consumer box. The wire however is a twin black and a red. So one black is neutral and the other is earth. Confusing really...

 

[JohnD]

It looks to me as if the grey cable from the junction box to the CU is flat PVC Twin and earth, so does it contain red, black, and an earth? i can't make out what the cores are connected to in your JB.

The glands on the round steel Besa box look like it is a professional job, but pretty old.

BTW it looks to me as if the supply to the shed does NOT go through the RCD (try turning the RCD off to check). This is a serious safety flaw. However it can be fixed without too much trouble.

edited - saw your note re core colours... a bad sign. One of the black cores may have had a black sleeve pushed over bare copper (it should be green and yellow). It will bne the one in the middle, if the cable is flat. Next time you have the power off see if the sleeving is loose and will pull off so you can replace it with G&Y. it is important to match the core colours up all the way through.

I believe your CU is Marbo brand, is that right? About how old is it?

 

[fosterweb]

Indeed I thought it was a little confusing to have twin black, never seen that before.

So if I trip the RCD, all the rings protected by the RCD will be disabled? So if the shed remains live then it is not protected, I will test that tommorow, hope it is protected however or it's more work for me!

EDIT: Noticed your last bit, the box was fitted last month, before that we had fuses, so it's brand new. And yes it is Marbo