In view of what I said before, I'm rather surprised to hear that your Option 1 was consdiered by electricians. Apart from anything else, as I think BAS was implying, I'm not at all sure that you would find 80A MCBs for any domestic CU. Many manufacturer's only go up to 50A, although at least a couple do 63A ones - but I've never seen anything bigger than that. Assuming that your current CU is adequate/sufficient for you main house needs, it also would seem to be an unnecessary hassle and expense to replace it, just so that the second CU could be fed from it.
Maybe - but the issue of earthing arrangements for outbuildings is a complicated, and sometimes controversial, business, and needs expert design - particularly when, as clearly will be the case, there are to be water pipes in the outbuilding.
Fair enough. However, even if 80A MCBs which will fit domestic CUs exist, it still strikes me as a very odd way to do it, particularly if it involves the (otherwise unnecessary) replacemnt of a CU.
You may not have to change it even then. If you simply require additional circuits which it will not accommodate, you could consider having (another) additional CU, fed from Henleys.
The 'differences of opinion' don't really relate to conflicts between regulations. The main issue relates to whether one uses ('exports') the earth of the house's electrical installation for the outhouse, or whether one gives the outhouse it's own totally separate earthing sysem, with local earth rod(s). There are pros and cons of both (in terms of safety) and which is considered better/safer will usually depend upon the specific circumstances of your situation - although not all electricians will necessarily agree in any particular case!
Fair enough.
I could attempt to explain some of the issues, if you wanted, but you probably don't want/need to know about them. The most important thing for you to understand is that you might not get the same opinion from different electricans, yet none of them may necessarily be 'wrong' (in terms of regs or anything else). I would suspect that, particularly given the presence of plumbing in the outhouse, electricians would probably be more inclined to advise the second option I mentioned (having a separate, local, earthing system for the outhouse) - but I may be wrong!
Assuming you're talking about the separte earthing of the outhouse, I don't think that would impact significantly on your landscaping. On the other hand, if they went with the other option (exporting the house's earth to outhouse) and decided that the earth cable already installed (between house and outhouse) was not adequate in size for that purpose, then they might have to dig up your whole garden to install a new cable!
Knowall does seem to have a rather odd fixation over the publication of the eighteenth edition of BS7671.Not to worry, by the time you makeup your mind we'll be working to the eighteen edition
No way Jose! This is being done come hell or high water in November, unless 18th edition comes out before then, in which case I'm screwed!
You previously seemed to indicate that there was an earth cable separate from the power (L & N) one. Is that what you are talking about, or is it, perhaps, 3-core 25mm²?
Agreed.
You're obviously not superstitious! I was brought up not to tempt fate
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