Well for when the cpc gets used for something else
Eh? What 'else' might you have in mind?
Well for when the cpc gets used for something else
... and timer fans - but put on a flak jacket before you mention it, even though it is 'regs compliant' (if appropriately sleeved at terminations)Plumbing controls
I am.Yep, that too.
Are you asking whether a 1.5mm² CPC is always adequate for a circuit whose live conductors were 2.5mm² (or 4mm²)?
We do assume that.If so, then that's an interesting question, which I doubt that any of us ever really consider - if the CSA of the live conductors is adequate for the design load, then we simply 'assume' that the CPC that comes in T+E of appropriate size will always be adequate.
Quite.I don't know whether it ever happens in practice but I suppose that, in theory, the CPC of T+E is not always (adiabatically) adequate. The required CSA depends upon I²t and, as far as I am aware, I²t continues to rise ('indefinitely') as PFC rises. Since there is 'almost no limit' to how high PFC can be (one sometimes sees figures of 'thousands of amps mentioned), I presume that it is 'not impossible' (with a very short circuit in an installation next to a substation) that it could be so high that the CSA of the standard CPC was inadequate. However, I cannot recall having even seen/heard anyone even considering that possibility.
Not sure I follow that.That's easy, but you're perhaps asking the question the wrong way around. The point is that, in adiabatic terms, the live conductors are 'oversized' - but, for those live conductors, there is also the consideration of the ('continuous') current-carrying-capacity (the antithesis of 'adiabatic'). In other words, considering 2.5/1.5mm² T+E, 1.5mm² would be adiabatically adequate for the live conductors, but the cable would then only have the CCC of 1.5mm² cable, not that of "2.5mm²" cable.
Yes.You mean flex?
Yes. As above, they must always be larger than actually necessary.If so, that's another 'good question' - since theory would indicate that the same 'conventional relationship' between CPC and live conductor CSAs would be just the same as in T+E.
Indeed - but, as I said, at least in theory (I don't know about 'in practice') the CPC of T+E is not always going to be adequate.I am. ... We do assume that. .... IF it is adequate then that must mean that the CPCs in other cables [and if using the same size singles CPC (as live conductors) because we do (not sure if that is just habit or normal practice to avoid calculation)] is always over-sized.
"CCC" and the maximum current a conductor can safely cope with under adiabatic conditions are two very different things. "CCC" (Iz - or, in fact, at least 1.13 x 1z) is the maximum current that a a cable is deemed to be able to carry safely for a continuous/indefinite period of time - and will inevitably be less than the current that it is deemed to be able to 'safely' carry under adiabatic conditions (i.e. conventionally for no more than 5 seconds - and for no more than 0.1 seconds if one goes by 434.5.2).Not sure I follow that. 1
That might sometimes be a small consideration - but with a short final circuit in a TN-C-S installation there would be very little difference between the two.Plus, the PSCC would be higher than the PEFC.
Indeed. If the CSA of CPCs in T+E is deemed to be 'adequate', then those in all flexible cables >1.0mm² must be appreciably 'more than adequate' (aka 'over-sized').Yes. As above, they must always be larger than actually necessary.
I have a drum of flex here, for a long time, which does indeed have a smaller CPC.You mean flex? If so, that's another 'good question' - since theory would indicate that the same 'conventional relationship' between CPC and live conductor CSAs would be just the same as in T+E.
Kind Regards, John
Interesting. In some senses 'consistent' (with T+E), but I must say that I have never seen, nor even heard of, such an animal.I have a drum of flex here, for a long time, which does indeed have a smaller CPC.
I purchased since 1974 as I remember the car I had when I got them. Originally a dozen reels of which I fitted plug & socket (XLR) on one, the rest have been used for installation work. I have every expectation it is harmonised but over 40 years I hay be wrong.Interesting. In some senses 'consistent' (with T+E), but I must say that I have never seen, nor even heard of, such an animal.
Does the cable in question have harmonised colours?
Kind Regards, John
Yes indeed - I also purchased the green and yellow.No green/yellow?
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