Pls help identifying T&E cable size.

[Tough Guy no. 1265]

As a percentage, the voltage drop is lower. If you had the same current at 12 volts, you could lose a sixth of the voltage with only 2 volts missing. 238 volts would be fine.

[spuorgelgoog]

I wish :-(

Owain

[John Rumm]

Might be a different storey in jock land... ;-)

[Robert]

Yes agree spot on. Rough calc is:

11grams divide by 9 g/cm^3 = 1.2 cm^3 (cubic cms) = 1200 mm^3 1200 mm^3 divide by 200mm = 6 mm^2 cable.

Errors: even if 2g out on weight wouldnt take cable much below 5mm^2 which I dont think exists.

Accuracy could be improved by stripping other core and checking the combined weight. Should of course be twice one core but would show up any zeroing errors on scales. Apologies for maths and experimental error lesson !!

[ARW]

There is no requirement to oversleeve old colours when being reused.

[ARW]

I would not be bothered by the distance but by the CCC due to the installation method.

[ARW]

And the cable size is dependant on the installation method.

Re do the calc with a cable clipped to a wall and you can use 4.0mm T&E for a 8kW shower

[Dave Plowman (News)]

Is it allowed to use ancient cable such as this for what appears to be a new part of an installation? Didn't the size of the ECC increase even during the lifespan of metric? So any modern calculators etc ain't going to be accurate?

[ARW]

You are no longer supposed to install cables that use the old colours (imperial or metric). You can certainly re-use ones that are already installed as part of an alteration.

ECC = cpc :-)

It makes no difference that the cables are imperial as you would do the calculations for the sizes you have - with a pen and paper if required - "Please Sir can I use a calculator for the square root bit of the calculation?"

As RCD protection will almost certainly be required for the OPs circuit then a smaller cpc is irrelevant in this case. The RCD protects the cpc.

Regarding the increased size of cpcs in modern cables it is worth noting that 2.5mmT&E did have it's cpc increased from 1.0mm to 1.5mm - I am not aware of any other metric cables being changed. However this is probably due to a ring circuit design fault (ie the one circuit that by default nearly always uses 2.5mm T&E).

A final ring circuit that used the maximum length of 2.5mmT&E allowable for voltage drop could not pass the adiabatic calculation with a 1.0mm cpc when the protective device was a 30A rewireable fuse (the BS3036 ones).

Cheers

[Dave Plowman (News)]

Snag is the OP seems incapable of measuring a cable strand accurately - and talked about using the TLC calculator.

If you can be certain he'll use an RCD.

Yup - that makes sense. Nudged my few remaining memory cells. ;-)

[Mike Clarke]

Yes, the sums look right but this doesn't fit in with the OP's description of it having a single core cpc approx 1.5mm dia.

Looking at imperial cables in table 5 of my old 13th edition regs the largest cable with a single core cpc is 3/036 but this can't be the case here because we have 7 strand conductors.

A 1.5mm diameter conductor would have a cross section area of 1.77 mm^2 or 0.0027 in^2. This is close to the area of 0.003 in^2 required for a cpc in 7/029 but I don't know if 7/029 with a single core earth ever existed.

As others have said the only safe way will be to measure the conductor sizes accurately to see if they match any of the standard sizes.

[AL_n]

Mike Clarke wrote in news: [e-mail]:

If there are any psychic peeps reading this, please tell me where I put my micrometer! I did compare my piece of stripped 7-core with the clean-cut end of some 6mm T&E in Wickes today. It looks almost identical. It's possible that my imperial 7-core is a few thou thicker. It's definitely not thinner.

One thing that puzzled me a bit is that while the TLC site says that 7.5KW is the most powerful shower you should run with 6mm^ cable, the blurb on the side of a Wickes' shower box says it "recommends" using 10mm^ on anything more than a 8.5kW shower. That seems to imply that I could use 6mm cable for an 8.5kw shower. Any comments on that?

Al

[AL_n]

"AL_n" wrote in news:XnsA4C0C82629ACAzzzzzz@130.133.4.11:

PS....

The table shown at the lnk below says much the same.

So it looks like I could install an 8.5kw shower, assuming it's 6mm cable. Anyone agree?

Al

[ARW]

You could install a 10500W shower with 6mm cable if you did it properly.

The gainsborough link is not worth a toss.

[Andy Burns]

Depends, if everything was "ideal" you could even get away with 4mm^2 for 8.5kW. You've already told us the length, but not the fixing method or any other factors that might require de-rating the cable (running in or through insulation, grouping with other cables, etc) does it have fuse or MCB, does it have RCD

Are you re-using an installed cable as some have asked, or hoping to use some old cable you have knocking about? As there's still doubt whether what you have is approx 6mm^2 or not, you could buy 10mm^2 cable for under £2/m and give yourself a wider choice of shower ...

[AL_n]

Andy Burns wrote in news: [e-mail]:

I've only been able to find 10mm cable for about ?40 for 12m... If I can get it for ?2/m I might just do that.

The cable runs from the shower, up plastic trunking to the loft. It then runs accross the loft (loose) and then down some plastic trunking to the consumer unit which is an old type fuse box fitted with circuit-breakers. It does not have RCD.

Al

[AL_n]

"ARW" wrote in news:mm71mf$vdp$1@dont- email.me:

I must say, I just read some electrician saying he has "installed loads of

9.5kw showers on 6mm cable, and never had a problem".

Al

[Andy Burns]

P&P extra, of course.

[ARW]

^^^^^^^^^^^^^^^^^^^ That stops you fitting an electric shower.

[Charles Hope]

But you can add a "stand alone" RCD.