Perhaps not. However, as you say, we don't know the temperature coefficient of resistance of whatever material they use for the element. However, 'they' (presumably!) do know - so they, but not us, could calculate the current/power at a specified operating temperature (and voltage) from their 'cold' resistance measurement.
True [8816, actually, per winston] - but I was thinking that the temperature difference of the element due to the 10V voltage difference would also be pretty tiny, particularly given that the temp is, I imagine, largely determined by the intimate thermal contact with surrounding water (without which the element would, in the absence of a thermostat or thermal cutout, undoubtedly be 'red hot' at either voltage!.
Clearly not - but, as Learningspark's question implied, whether one could just spend that £3 depends upon whether the cable is up to whatever £3-worth one is planning on buying/installing.
True, but unless the OP is prepared to have it replaced, the cable obviously is.
You can have either of those.
No it isn't.
Yes, I presumed that was the situation and what you wanted to know and, I just wrote, you have really already been given the answer to that ... any shower rated at 10kW or less at 240V (which corresponds with 9.2kW or less at 230V) would be OK (at 230V, which is the voltage we are meant to use for such calculations) with a 40A MCB.
You've lost me! If the cable had a CCC of 47A, in what sense would "the existing 40A MCB [be] the highest-rated one that the present cable will support", which is what I wrote, and what you quoted??? Wouldn't that cable support a 45A MCB (and I believe that 45 is greater than 40!) ?
Again I'm a bit lost - I didn't realise that it was acceptable to have a cable with a CCC of 47A protected by a 50A MCB
Indeed - I've just pointed that out to the OP.
I was merely answering the OP's question as it was written. Obviously, with a 40A MCB, he can't have a shower rated higher than 40A but, as I have said, that 40A MCB is not his deciding factor. He wasn't asking about the cable.
It would but I presumed you didn't mention 45A MCB because they are not universally obtainable - which I thought would have been your response had I brought them into the conversation.
Yes you did. The shower cannot cause an overload.Again I'm a bit lost - I didn't realise that it was acceptable to have a cable with a CCC of 47A protected by a 50A MCB
Only after I did it first.
Well, if one takes the view (as you mentioned subsequently) that one can use as high a rated MCB as one wants (provided it provides adequate fault protection) if the load is not capable of causing an overload, I suppose that one would have to agree that the MCB was not the deciding factor'!
Hmmm again. I realise that's strictly true, but I don't think many electricians actually adopt that approach. If they did, they could buy a job lot of 50A or 63A MCBs (if available for the CU!) and use them routinely (Zs permitting) for immersion circuits, shower circuits, (non-fan) cooker circuits etc., regardless of the CSA of the cable. I seriously doubt that many would do that, even though you could argue that it was regs-compliant.
Fair enough, but I hadn't see your post at the time - honest, guv!
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