Supply to garage/Black conduits

[Ambergreen45]

I have a supply of electricity to the garage at the bottom of my garden. There is no separate consumer unit for it. The power comes from the mains fed through the first socket which has two cables coming from the main, ie 2 red, 2 black, 2 earth, and then 1 red, 1 black, 1 earth leading to the middle 13A fused switch. In total within that double socket there are 3 live cables joined together, then 3 neutral and finally 3 earth.

I have taken out a light cable from the middle 13A fused switch (wall light no longer necessary and wasn't really working for some reason). The last 13A fused switch on the right (Pic 1), has a cable that leads to the garage and is fed in turn from the middle 13A fused switch. That's the way it has always been.

Now that I have removed the light cable (probably 1.5 mm2) from the middle 13A fused switch, should I still leave that middle switch there? Perhaps it should still be there for a reason (and it will save me some work). That means that I still will need to switch two switches in the house before going into the garage to switch anything on.

Also, what could that vertical long metal conduit be for (Pic 2)? I've been scratching my brains... It was buried in plaster and I just came across it when I was removing the light cable from the wall. The outside cable that leads to the garage is somehow at the same level as the socket on the wall.

A final question, why are there two conduits below the socket and fused switches? The one on the left seem to be of the same material used for underground cables leading to consumer units, and that's the one directly underneath the double socket. The one on the right (underneath the last fused switch on the right) is in metal and looks like is part of the long vertical pipe.


Many thanks.

Electrical 1-3

• Ambergreen45
• 8 Dec 2012
• 1

Electrical 1-4

Electrical 1-3

• Ambergreen45
• 8 Dec 2012
• 2

Electrical 1-3

 

[ericmark]

There are two basic types of circuit.

Ring

Radial

With a radial remove the wrong wire and some thing stops working.

With a ring remove the wrong wire and the cable can over heat and burn out.

So you need to work out if radial or ring before one can answer your question. The ring can often be accidentally split for years without anything going wrong the one day just a few too many items are used and cable melts. This is why on change of occupant or every 10 years which ever the sooner we check out the whole system.

In theroy you should have an installation certificate, periodic inspection report, or electrical installation condition report which will tell you if ring or radial.

In the main rings have a 30A fuse or 32A MCB where a radial has a 20A fuse/MCB but not always.

Both rings and radials can have fused and unfused spurs the latter only ever feeds one device and the fuse in the plug or FCU stops over load.

There are exceptions to nearly every rule and using thicker cable radials can have same fuses as rings.

Once one moves in a garage then you can get all sorts of mixtures. One site my son worked on were feeding a 4mm SWA with a 2.5mm flat twin and earth so one does have to be careful and not jump to conclusions.