2.5mm flat cable with a sleeved CPC

[John-SJW]

I recall seeing this a long time ago. Is it still available? Anyone know.

 

[pc1966]

Having full-size CPC is basically wasted copper. The CPC exists to clear a fault, and if the circuit is designed to meet the required disconnection time / let-through energy then larger is simply not needed.

For some things, like long extension leads, that disconnection characteristic might not always be met, and for other practical manufacturing reasons reasons you might choose to make them all the same size.

 

[John-SJW]

I think you mean sized large enough to activate a disconnecting device.
Electricty always wants to return back to where it orginated - the generator, transformer, battery, etc. The earth wire was to parallel the Neutral return to the generator or origin - either full, all geh way back, or party by connecti g to the N at some point on its way back. So that if there is a fault, it gets back to where it came from. So it needed to be the same size as L and N. Seems modern disconnecting safety devices have changed the view.

 

[Sparky Pat]

Before the days of green / yellow I do recall having some 1.0mm single and earth where the earth wire was sheathed green.

 

[telectrix]

The metric system is crap. I am 183 cm high and 76 kg.

impossible for me to visualise those measurements.

e.g. a gallon of water weights 10lb. sssimpless. but 4.54l weighs 4.54 kellogs, stupid.

 

[John-SJW]

impossible for me to visualise those measurements.

After all this time? Metric is easy. You just gave a simple easy e.g., as well. Very easy. Learn it, it is simple and quick. Everything matches.

 

[telectrix]

Everything matches.

as did the Titanic's watertight doors.

 

[westward10]

I remember back in the late 80s probably where we used some 1.5 and 2.5 with an insulated cpc. No idea of the manufacturer and I had kept some but no idea where it is now.

 

[brianmoooore]

I only know my exact height in feet and inches. I have an idea what it is in metric units, based largely on comparison with fluorescent tubes.
I know my exact weight in Kg only. I have no idea what it is in various weird imperial units.

 

[Intoelectrics]

I use metric for precision and imperial for rough measuring. e.g. a 2400 x 1200 sheet board I call an 8" x 4"

A little trick I use so I don't cut some thing short is to measure it in metric millimetres for precision and then I use the imperial inches as a reference point. For example if I want to cut something 1110mm, so I don't mistake it for 1010mm I'll round up to the nearest inch as a ref point = 44"

 

[John-SJW]

Dave Savery covers it here, about half way through. The Irish went over to insulated CPC with it having to be the same size as the L & N. I believe the Australians do the same but use stranded cable. That must really push up the costs.

 

[ElectroChem]

I believe the Australians do the same but use stranded cable. That must really push up the costs.

Indeed we do. Twin and Earth with G/Y insulated earth is standard here. Same size earth from 1mm-2.5mm2, then smaller from 4mm+. Biggest I've seen was 16mm, but 6mm is the largest in common use for things like 32A oven circuits.

 

[brianmoooore]

I remember back in the late 80s probably where we used some 1.5 and 2.5 with an insulated cpc. No idea of the manufacturer and I had kept some but no idea where it is now.

Would this be in one of the copper shortages, when we were using cable from wherever it could be sourced?

 

[brianmoooore]

I use metric for precision and imperial for rough measuring. e.g. a 2400 x 1200 sheet board I call an 8" x 4".

And if it's plywood, you'll be right!
Applies to the cross section of timber as well. No one asks for 200 x 47 in the merchants - it's 8 x 2, and the length is measured in 'metric feet'.
When I come back from holiday (remember them?), I don't only come back with enough booze to stock a pub, but also three or four tape measures, which, of course, are metric only.

 

[pc1966]

So it needed to be the same size as L and N. Seems modern disconnecting safety devices have changed the view.

No, as the CPC never carries the current for any significant length of time. Even for the odd case of a N-E fault and then an open N you would be disconnected on the RCD in most circuits so the CPC never needs "overload" protection, only ever fault protection.

In some ways "modern" protection is not as effective as the fuses for hard faults, thier let-through I2t is generally less than MCB/RCBO.

In the case of T&E when used in domestic situations (i.e. energy-limitng MCB and PFCs under 6kA) you simply don't need a full-size CPC, which is kind of the point of standard circuit designs (e.g. the OSG table). Yes, you have special cases if the CPC is also bonding extraneous parts under PME supply conditions, but as that already needs 10mm by UK regs so full-size CPC is not helping there.

I would be genuinly interested to know what the reasoning/justification was for ROI adopting the same size of CPC and pushing up costs. Anyone know?

As for the sleeving issue, yes it is a bit tacky having to add it. But equally it makes the overall cable smaller and more easly routed, and I guess it also makes cable damage (e.g water ingress) and RCD detection of it a little better.

 

[John-SJW]

The British Approvals Service for Electrical Cables (BASEC) operate the approvals service for Southern Ireland. The country is too small to justify operating its own approvals organisation so the British do it for them, doing both countries. So I can't see why this insulated cpc Irish cable is not available in the UK. BASEC do not approve cables that do not meet UK standards, so I read.

So why no cable on sale in the UK? mmmmm