Far rmore usually near the 230V mark here. Can be down towards 220V in some places; up towards 250V in others. Also fluctuates at different times. It's a nominal voltage for a reason. It's never constant.
Lighting earth issues - could I just run a fused spur from the power circuit
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A rock solid 240 to 242v here. 230v oven lamps, last no time at all, if they are not marked 240v, no point to buying them.
"Rock solid" yet fluctuates... But you can't seriously be claiming that it only ever fluctuates within 2V. Complete horseshit if I'm honest.
I don't sit there for hours, watching it, but on those occasions I have checked it, it is always within those bounds. Some small variation, is unavoidable, due to my own loads turning on and off, though less so if measure at the CU, which I never have bothered.
Yes, that's kind of what I've already done as a temp fix. I simply have an earth wire run from the light switch to the earth pin of a three pin plug and leave it plugged in. I don't know whether that could be made into something more permanent (ie concealed), but at least it's obvious what's being done this way.
Eventually I'll probably sort the lighting cables out (depending on disruptive future access) so 'borrowed earth' may be a better interim solution than using the spur method.
Thanks all for your further thoughts here. Seems I actually have plenty of options to consider.
Better than nowt, though not much better - what if someone needs to make use of the socket, and unplugs it?
I wouldn't claim 'rock solid' but I have rarely, if ever, seen a voltage less than 240V on any of my phases - most commonly around 243V-245V.
Well, I would call that rock solid. Certainly beats the 230 - 250v reported below...
So would I, IF I had written "always 243V-245V", but what I actually wrote was "most commonly 243V-245V" - which is obviously a very different kettle of fish!
The totality of the reality is that it sometimes goes down to 240V/241V, and and occasionally up to about 250V - so, roughly, 240V-250V
Yes, even my 'reality' does beat that.
I must say that I often wonder why most domestic installations seem to have relatively small degrees of variation, with supply voltages 'as high' as they usually are, and that leads me to further wonder whether the DNOs final bits of network are as 'efficient' as they could be - I would rather have expected them to use cables, and number of installations per cable, such that at times of peak demand, the voltage at the furthest installation fell to fairly close to 216.2V (and probably rise up to 240V+ (maybe even closer to 250V) during times of least demand).
Since I rarely, if ever, hear of variation anything like as large as that, it sounds as if they use cables that are quite a lot fatter than they actually need to be for the number of installations being supplied?
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By fused spur, I guess you mean a fused connection unit attached to a radial or ring final circuit, in which case you'd be limited to 13A.
I can think of a few potential reasons for that.
Firstly if a cable is highly loaded then
Firstly, if a cable is consistently highly loaded for many years energy losses can significantly outweigh the cost of the cable. Lets say a cable carries 50A continuously for 50 years. Over it's lifetime it will experience about 1 billion A²h. With 16mm² copper cable (I know the electricty cos use aluminium, but that just makes the point even stronger) that translates to around 1.15MWh per meter lost in each conductor. Lets assume that cable has four conductors three of which are loaded. that is around 3.45MWh per meter Wholesale prices of electricity vary but are currenly hovering around £100 per MWh so over it's lifetime that cable will have around £345 per meter of losses. If we increase that to 25mm² that drops to £128 per meter. For comparision tlc sell 16mm² 4 core SWA is about £10 per meter and 25mm² (and those prices are retail) for about £16 per meter and I suspect the suppliers pay much less.
For cables serving a single domestic property we don't tend to think much about this because the cables are low duty cycle, but for cables further back in the system where the load is more uniform this is a real consideration.
Secondly, installing cables is expensive. For smaller sizes the cost of laying the cable can be comparable to or even greater than the cost of the cable itself. So you don't want to have to install a cable only to have to replace it with a larger one a few years later.
Thirdly, the voltage has to be in-spec for the customer furthest from the point of voltage regulation. If we assume customers are evenly distributed from the point of voltage regulation to the end of the line, then the average customer will get significantly less volt drop than the worst-case customer.
True, and that obviously remains qualitatively true even if the cable is not 'consistently highly loaded'. However, I would have thought that, in the real world, DNOs would probably be far more concerned about immediate capital outlay rather than 'running costs over several decades, wouldn't they?
Again true - but, again, I wonder if the need to 'upgrade' the cable is likely to occur soon enough to outweigh the immediate capital cost of such 'future-proofing'?
Sure - but, as I've said, whilst supply voltages in the fairly high 240s are not that unusual, at some times and for consumers fairly close to the transformer, I have personally never seen or heard of supplies anything approaching as low as 216.2V for those at the end of the cable, have you?
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