Thanks ....
Old Imperial "7/.029" Twin and Earth
- Thread starter aesmith
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Does that mean you are installing it off the roll, as new?
1/.044 = 0.98 sq. mm
3/.029 = 1.28
3/.036 = 1.97
7/.029 = 2.98
7/.036 = 4.60
7/.044 = 6.87
7/.052 = 9.59
7/.064 = 14.53
19/.044 = 18.6
19/.052 = 26.0
19/.064 = 39.4
These figures are based on calculation of the c.s.a. of each strand from its diameter. If you use the nominal c.s.a. figures from the 14th edition table above you'll get slightly different results.
Not new, mostly it's in place but there are lengths that I've removed from their original places during the process of tracking down exactly how it was all wired, and reorganising into what I consider a safe design.
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Close enough, I made that 1.9mm, you make it 1.97 which I'm sure is correct. Either way it's greater than 1.5.
As you say, close enough and makes the point.
I always felt that the old 3/.036 and 7/.029 were "nicer" sizes in many ways than the metric replacements, where sometimes 1.5 or 2.5 is a little too small but going up to 2.5 or 4 respectively results in a cable size which seems rather larger than necessary. The smallest size conductor used for normal power wiring here in the U.S. is 14 AWG, which at just a shade over 2 sq. mm equivalent is very close to the old British 3/.036 size (albeit that it's solid rather than stranded).
One thing I always felt was wrong was the way that with the publication of the 1970 revised metric edition of the 14th edition Wiring Regulations the IEE just completely removed all the reference material for Imperial-sized cables, as though they were just going to cease to exist overnight and nobody would ever have to add new metric-sized wiring to an existing pre-metric installation. As your queries demonstrate, here we are over four decades later and there is still a need for such information. Why couldn't they have relegated the old Imperial material to an appendix so it would continue to be available for easy reference in future editions?
I always felt that the old 3/.036 and 7/.029 were "nicer" sizes in many ways than the metric replacements, where sometimes 1.5 or 2.5 is a little too small but going up to 2.5 or 4 respectively results in a cable size which seems rather larger than necessary. The smallest size conductor used for normal power wiring here in the U.S. is 14 AWG, which at just a shade over 2 sq. mm equivalent is very close to the old British 3/.036 size (albeit that it's solid rather than stranded).
One thing I always felt was wrong was the way that with the publication of the 1970 revised metric edition of the 14th edition Wiring Regulations the IEE just completely removed all the reference material for Imperial-sized cables, as though they were just going to cease to exist overnight and nobody would ever have to add new metric-sized wiring to an existing pre-metric installation. As your queries demonstrate, here we are over four decades later and there is still a need for such information. Why couldn't they have relegated the old Imperial material to an appendix so it would continue to be available for easy reference in future editions?
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I've been concentrating on the power circuit, I think I need to check the lighting as well, I just assumed that was 1mm² when I was connecting that.
By the way, what data were people looking at which suggested the CPC would be smaller than current practice?
By the way, what data were people looking at which suggested the CPC would be smaller than current practice?
I well remember using the old 7/.029 (even the real old black rubber sheathed stuff!). IIRC the CPC was 3/.029, and all the conductors were tinned copper to boot! To be honest, I used to curse (the new) 2.5mm² as it was less flexible than the old imperial cable.
It was 3/.036 earth with 7/.029 - See Table D2 from the 14th edition which I posted above.
The standard make-up of T&E cable when it first went to metric. I'm afraid I don't have a scan of the relevant table to hand, but 2.5 sq. mm T&E was made originally with 1 sq. mm earth (now 1.5 sq. mm).
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