OK the first one seems to come up fairly frequently:
Just the one comment, the maximum earth fault loop impedance figures are those as published in BS7671, do you think there should be any details on correcting these for operating temperature, or even putiing the rule of thumb
0.80 corrected values in as in the On Site Guide?
Yes. I have updated it. Thanks
I don't know if this is worth mentioning, but if I am asked about one, I want to know the rating of the main supply fuse, the CU and also what else is in the house. A neighbour's boyfriend just bought one without any thought: fuse 60A, electric cooker and about 30A of storage heaters - the shower was 9.5kW. I might be wrong, but a small house on a small fuse and the diversity of storage heaters...!
if available":-)
And yes I always forget to add a comment even for spelling corrections.
Take great care if using pliers etc to bend and shape wires to not damage or knick the insulation while doing it.
nick?
[g]
lol, surprising how one missing letter can change the whole tone!
That's what pikeys do to the conductors?
Personally I'm not completely happy calculating for an appliance rated at x Watts at 230 Volts when I know it's going to actually get 240 Volts through it.
Owain
240V across it, not through it. The Ladybird Book of Electrics is that way>>>>>
:-)
245, here. We're very close to the substation!
Generally with the larger appliances like showers etc that causes the design to be slightly conservative since the makers usually state the actual power at 240V.
E.g. shower which delivers 9500W at 240V will draw 39.6A, but you design as if it draws 41.3A. (in reality a 9.5kW shower would probably run at under 9kW on 230V)
A question I fear will probably display how little I understand: would it be (i) right and (ii) worthwhile to add a para. about the special provision for ring final circuits using 2.5mm T+E etc being deemed to be "OK" in certain circumstances so long lz as installed is >=20A? I thought there was something about this in the Wiki but can't find it now.
It might be worth adding a note that the article as a whole is really focussed on the times where one of the "standard" circuits in the OSG (of which 32A/2.5mm^2 rings are one) are not appropriate.
I can't think of many cases where you will be designing a specific circuit using conductors in parallel in a domestic environment, and even if you were, the specific "deeming" of compliance by BS7671 at a slightly lower Iz (i.e. 20A rather than half of 1.45 x 32A) permitted for ring final circuits would not apply to your circuit anyway.
It is worth noting that the fuse wll not blow at 60A. A 60A BS3036 fuse will pass 120A for about an hour before tripping.
Just a couple points about the shower one:
NT
Might need a special article for those ;-)
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