Adding spur to power attic...

[toasty]

Mate,

Not sure what you mean when you say they draw a lot of power but are low current, that's impossible, the two things (power and current) are directly related.

Also, and not meaning to sound condecending, but if you don't fully understand power, current etc... perhaps get an electrician to check your work.

 

[andru]

Heh, alas funds certainly don't stretch to an electrician.

Fear not - the days of GCSE physics may be long behind me, along with all the i/VxW^2 stuff, but I've got enough experience in wiring stuff up to not kill myself. I hope

Nah seriously, I'm quite willing to admit I know very little of the theoretical stuff, but I'm capable of doing the wiring - hence the need for advice I get what you mean about the power thing, a memory of P=VxI (or something to that extent) flashed before me as soon as you said it. It's after the transformer when it steps up to a very high voltage (what I meant when I said power). I'm just being very wary about all this. Electricity isn't something I intend to take lightly.

 

[AdamW]

Personally, I would advise against using 1.5mm from your spur. It is technically fine, will have no problems handling the power. But you never know if someone will come along in future and think "Ah, 1.5mm. Lighting circuit. I'll just cut this wire and tap into it here... Pull the lighting fuse will you dear?" *snip* *BANG*

For the sake of a couple of pence a metre, go for the 2.5mm. It is no more difficult to work with than 1.5mm.

Of course it depends on the run you take, but seeing as you are likely to run it above the ceiling for at least part of the way, I think it is a worthy precaution. By using 2.5mm you could be saving the life of an incompetent DIYer years from now...

 

[ban-all-sheds]

I'm guessing the remaining 4 15a fuses are 2 pairs for radials - one for each floor?

Radial circuits do not have pairs of fuses, and neither do rings (although I have seen it suggested as an alternative method that would also protect against unbalanced loads on a ring).

How many cables are connected to each fuse?

If you pull one out, what stops working? You need to find this out - guessing what fuses are for, and therefore how to isolate circuits, is an unsafe practice.

So, if it is a radial circuit, how do I go about extending it? If it helps, I'm perfectly happy to sacrifice a socket in the room below, as it's in a pointless place anyway.

If it is a radial circuit, than you can simply extend from the last socket, or branch off from any existing socket, provided you stick to the same cable size, which for a 15A rewireable fuse would be either 2.5mm² or 4mm², depending on the length of the circuit (35m & 61m respectively). You will have to watch the floor area served - a 20A radial is limited to 50m² - I don't know what the limit is for a 15A radial.

I note you have no RCD. This is not ideal.

 

[Damocles]

Radial should go:
fuse-socket-socket-socket-more sockets and then just stops.

ring goes:
Fuse-socket-socket-more in the middle-socket-back to same fuse

The nice thing about a radial is that you can just spur off it anywhere and keep going. (though nicer to do it all in a line, easier to test.) No fuse needed for the spur because all cables are rated to carry the full available current.

Use the same size cable as existing.


Just check that the fuse for the shower does NOT power anything else.


You should make a list of which fuse does what. Might need it in a hurry one day. Might be something written inside the lid of the fusebox.