how long is a piece of string

Thought I would give the obvious answer as a topic

Saves someone else typing it

Anyhow, have just completed rewiring the downstairs, upstairs and kitchen rings, in my dormer bungalow

What has suprised me was coming to the end of my SECOND 100m reel of 2.5mm cable

Have meters become shorter since the last time I did any domestic wiring ????

Or is my memory foggy

I cant remember using so much cable before

To the question - how much cable on average does it take to wire a domestic property ?? - just approximately

easier to answer your question about how long is a piece of string?

answer twice as long from the middle to the end

more sockets means you can't take the shortest route into and out of a room. More rings means more 'wasted' cable getting there.

150m might be a kind of "Average" for a domestic terraced house two rings and a small kitchen ring and a minimum number of sockets then you might go up from there.
Note - "Average" is the most dangerous word in the universe

swelec said:

Thought I would give the obvious answer as a topic

Saves someone else typing it

Anyhow, have just completed rewiring the downstairs, upstairs and kitchen rings, in my dormer bungalow

What has suprised me was coming to the end of my SECOND 100m reel of 2.5mm cable

Have meters become shorter since the last time I did any domestic wiring ????

Or is my memory foggy

I cant remember using so much cable before

To the question - how much cable on average does it take to wire a domestic property ?? - just approximately

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Lots, would be my answer. Have you also factored in coax, cat 6, alarm etc whilst you are in a mess. But now is the time to do it.

Sureitsoff? said:

But now is the time to do it

Click to expand...

Over 17 years ago is when it was actually done...

denso13 said:

Over 17 years ago is when it was actually done...

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Indeed - 17+ years may well be a record for 'resurrecting an old thread

Kind Regards, John

Well this piece of string seems to be long.

That is long time or 17 years maybe we'll come back to it in 2038.

SUNRAY said:

That is long time or 17 years maybe we'll come back to it in 2038.

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Unfortunately, I'm far from sure that you will be able to count me into that one

Kind Regards, John

The string runs down the centre of a cable, so clearly a cables lenght.

However in 2004 we were allowed 4% volt drop, now allowed 5% so how much cable in a ring final has changed, it was I seem to remember 80 odd meters, now 106 meters.

I know the rules on drilling beams resulted in more cable being used, and one way to reduce the cable required was ring final put side to side rather than up/down.

The problem however was use of just 2 RCD's, risk assessment means we don't want lights in any room to fail should some one get a shock from a socket circuit, and since lights normally split up/down unless using RCBO's one is forced to also split sockets to match lights.

Today we look at type B RCD for EV charging and can't get RCBO as even type F, so now even more to consider.

So the question is more revelent today than in 2004.

swelec said:

Thought I would give the obvious answer as a topic

Saves someone else typing it

Anyhow, have just completed rewiring the downstairs, upstairs and kitchen rings, in my dormer bungalow

What has suprised me was coming to the end of my SECOND 100m reel of 2.5mm cable

Have meters become shorter since the last time I did any domestic wiring ????

Or is my memory foggy

I cant remember using so much cable before

To the question - how much cable on average does it take to wire a domestic property ?? - just approximately

Click to expand...

If you did a "rewire", why did you feel it necessary to reinstall Rings rather than instal Radial wiring with individual RCBOs at the Consumer Unit?

See

Did you drop down to sockets or come up from below? That makes a huge difference.

The main reason for the ring final rather than radial is it allows one to use less copper. This has been the case since it was invented. However the BS 1363 will normally allow three 2.5 mm² cables to fit with ease, or two 6 mm² at a push, as to 4 mm² tabulated current carrying capacity (It) with installation method 100 is only 27 amp so it often can't be used.

So with a 32 amp radial you can't have spurs as the socket will not take the larger cable, and the maximum cable length for volt drop is 64 meters compared with 106 meters for 2.5 mm². But it means you can't add to the circuit, and in the main we find over time we want to add to the circuit.

If we look at a 20 amp radial with 2.5 mm² the cable length of 32 meters becomes a bit restrictive, so 2 ring finals at 106 meters each would need at least 6 radials with 20 amp radial with 2.5 mm² to cover same area. The RCBO cost increases as a result, and the size of the consumer unit to accommodate the extra circuits, also what is plugged in is restricted to have a washing machine and tumble drier on the same radial could result in overload.

So if rewiring a reasonably sized property with radials even if you use a radial per room, you still are likely to have overload, and the cost rockets. I remember pre-war wired houses with large fuse boxes, but very few sockets using 5 and 15 amp. It was basic a circuit for each socket.

I would think with this house 20 amp radials would be out using 2.5 mm² simply due to size of house, 32 meters would not be enough, likely it would need to be 16 amp radials and so 42 meters, and since back in 2004 only allowed 4% volt drop only 33.5 meters for a 16 amp radial with 2.5 mm² with 20 amp 26 meters, the ring final was only 86 meters back then.

So seeing how much cable he used would have needed 3 ring finals, or 8 radials, to cover the same area. I tend to think those who feel radials are better are not complying with volt drop requirements.

As to length of piece of string in UK 608 feet (185 meters) i.e. a cables length.

FrodoOne said:

If you did a "rewire", why did you feel it necessary to reinstall Rings rather than instal Radial wiring with individual RCBOs at the Consumer Unit?

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The post was over 17 years ago!!

Lectrician said:

Did you drop down to sockets or come up from below? That makes a huge difference.

Click to expand...

denso13 said:

The post was over 17 years ago!!

Click to expand...