Imperial T & E

[OnOff]

Old imperial T&E?

Was it, csa wise, 2.5mm,4mm, 6mm etc or an close imperial size? Sorry to be pedantic. I only ask as I have a length feeding a cooker connection unit and am considering whether to re-use on a cu change. So guessing is 4 or 6mm squared. Appears from the visible ends to be in very good condition and IR tests fine. No apparent breakdown either on the clipped direct stuff on the loft joists (weird metal clips). It's the type with the "silver" stranded cpc up the centre and the line and N again stranded and silver in colour but sheathed red/black. I can easily measure the csa of each strand and multiply to get the overall csa. The original install dates from 1960 and the T&E is all under metal top hat capping. Fuses have been replaced by MCB's. This old T&E looks like new condition wise. Can't say the same for the cloth 16mm meter tails, "crumbly" is the term I'd use! Thanks.

 

[PC Electrics]

Nothing wrong with reusing imperial t&e that is in sound condition.

Do not guess at sizes and capacities! We are not in the guessing game. Remember we have to certify our work!

Pay your forum dues, and then go to the downloads section. Here you will find a guide to imperial cable sizes and ratings that I created and uploaded about 2 years ago.

Imperial Cable Sizes and Ratings - Downloads - Talk.electricianforum.co.uk... a forum with a difference.

Your contribution towards the running of the forum will be appreciated by all.

 

[Technician]

Onoff; I have some tables that could be useful

to you with regard to imperial sizes. If you give

me some time I may be able to relay some

information to you.

Best Regards.

PS I have been promising this as a download for some

time; apologies, Manator.

But it looks like PC may have beaten me to it.

 

[PC Electrics]

I would ask that once downloaded you keep the file for your own private use and do not distribute it further.

 

[OnOff]

Nothing wrong with reusing imperial t&e that is in sound condition.Do not guess at sizes and capacities! We are not in the guessing game. Remember we have to certify our work!

Pay your forum dues, and then go to the downloads section. Here you will find a guide to imperial cable sizes and ratings that I created and uploaded about 2 years ago.

Imperial Cable Sizes and Ratings - Downloads - Talk.electricianforum.co.uk... a forum with a difference.

Your contribution towards the running of the forum will be appreciated by all.

Sorry, I know I wrote "guessing" but didn't mean it literally as in I'd go along with a guess without knowing for sure. Hence the "intent" to use the vernier on the strands. I've already paid to use the downloads a while back so am looking at your link now. Many thanks.

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I would ask that once downloaded you keep the file for your own private use and do not distribute it further.

Will do.

..........Just read your upload about using a vernier, seems I WAS going about it correctly!

 

[Evans Electric]

And OnOff , did you not luxuriate in the suppleness of the lovely stranded 7/.029 s of the ring main cables?

This was before our betters decided to not only go metric but to inflict the 2.5 solid core crap that we've had ever since.

 

[PC Electrics]

To be fair Ev, imperial cable PVC (and early metric) had a lot more plasticisers in it than they do today. It helped to make the cable more supple. But I agree - today I much prefer using 4mm stranded than 2.5 solid. And the old imperial stuff is a joy.

 

[ProDave]

Re the crumbly cloth covered meter tails:

Fit new tails between the CU and the meter (cough, it didn't appear to be sealed, cough) *

Then phone the DNO to report that you have found dangerous tails between the head and the meter. That will also get the meter re sealed.

* not usually an issue up here as most single rate meters are the ones with an isolator and only the input terminals are sealed.

 

[OnOff]

Re the crumbly cloth covered meter tails:Fit new tails between the CU and the meter (cough, it didn't appear to be sealed, cough) *

Then phone the DNO to report that you have found dangerous tails between the head and the meter. That will also get the meter re sealed.

* not usually an issue up here as most single rate meters are the ones with an isolator and only the input terminals are sealed.

NOT an issue, the seal fairy has no need to visit! Those nice people from BG came in to fit a smart meter AND fitted a nice Wylex REC isolator too.

 

[OnOff]

I had a measure up today of this cooker cable (fed of a 32A Wylex MCB, presuming, previously a 30A re-wireable as this, another 30A and a 5A are still in the bottom of the cabinet).

I noted the live (line) is 7 strand. Measuring an individual strand with the vernier and it measures at just over 1mm as per the picture.

Can't for the life of me read the imperial scale, though the "6" lines up - whatever that means! On the metric scale I make it 1.2mm? So.....I make the csa on a 1.2mm dia core 0.785mm sq. Then x7 for the 7 strands and I get 5.49mm sq for the line conductor. BUT that doesn't as far as I can see tie up as either 7/036 OR 7/044 on the table I downloaded. My measuring? I measured a strand on the section I took out of the top of the breaker so maybe it was a little flattened and I measured across the wider axis of an "oval"?

EDIT: Woops! Just realised my maths error I was working on 1mm dia rather than 1.2mm which I measured. So I now make the csa on a 1.2mm dia cable 1.13mm sq, then x7 gives me a nominal TOTAL csa for the 7 strands together as 7.9mm csa. So 7/044 looking the likeliest as someone suggested. Thanks to all on this one.

 

[Manator]

Standard imperial cable sizes; e.g. 3/036, 7/029, 7/0.036, 7/0.044, 7/0.052

These are strand diameter in inches and number of strands e.g. 7/029"

1 in

 

[kerching]

On the subject of 1 in2...back in the day we used to call [equivalent of...] 70mm2 point 1s, 150mm2 tails were point 2s....not a mind numbing revelation , but it brought back a few memories.... :Y

 

[ProDave]

Can't for the life of me read the imperial scale, though the "6" lines up - whatever that means!

The imperial scale is marked in 16ths of an inch.

And the vernier scale subdivides that 8 times again, giving a resolution of 1/128th of an inch.

So you have measured 6/128 of an inch, or 0.0468 inches. Which pretty well ties with your metric measurement of 1.2mm

So I would guess you have 7 / 044 cable that's been squashed a little.

The trouble with imperial measurements, are different instruments are calibrated in different fractions, making comparisons somewhat tricky (without a calculator)

 

[PC Electrics]

Sounds like you've got 7/044, which is what I'd expect for a cooker circuit.

 

[OnOff]

The imperial scale is marked in 16ths of an inch.And the vernier scale subdivides that 8 times again, giving a resolution of 1/128th of an inch.

So you have measured 6/128 of an inch, or 0.0468 inches. Which pretty well ties with your metric measurement of 1.2mm

So I would guess you have 7 / 044 cable that's been squashed a little.

The trouble with imperial measurements, are different instruments are calibrated in different fractions, making comparisons somewhat tricky (without a calculator)

Cheers for the vernier reading lesson! Just realised my maths mistake, I used a radius of 0.5 for the strand rather than 0.6! :coat

 

[steptoe]

when Im working out imperial for an EICR I use < or > and relate to metric, I find customers (and numpties) can relate easier, I once did one in imperial and a few months later had a landlord wanting to know why he need a rewire as someone had been doing some work and said as he had 'inch' cable it all had to be replaced with mm stuff!!!!!!

 

[Manator]

There is nothing wrong in producing a certificate with the words "imperial equivalent to 2.5mm", any inspector is left with no doubt that the cable size is not metric, and its actual size in most installs is pretty much irrelevant, providing that accurate test results are documented.

This does not mean that you can ignore the results and readings that you get, but helps to get over the fact that imperial measurements are beyond the majority of inspectors knowledge.

It did take me years to convert to metric, and I remember stating imperial sizes for many years until I eventually gave in.

 

[Evans Electric]

I did the same when money went decimal , kept converting back which is stupid really because the decimal

 

[springcrocus]

Cheers for the vernier reading lesson! Just realised my maths mistake, I used a radius of 0.5 for the strand rather than 0.6! :coat

Best advice I can offer - treat yourself to a digital vernier. They all read both metric and imperial, and can be bought for about

 

[OnOff]

Best advice I can offer - treat yourself to a digital vernier. They all read both metric and imperial, and can be bought for about