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The purpose for the 2 way switching was I getting fed up having to walk back to turn half of the lights off on the way to bed. You are probably right, I could reduce the number of 2 way switched pairs. The back boxes are 35mm can't go any deeper based on the wall thicknesses tbh. Thanks.

I want to have 2 x 1g 35mm box with 3 switches each 2 way switched from either end of the room. Im concerned about cable density in the back box so was considering fitting 3 x 3 core +e 1.5mm (because i have plenty) to each switch and do the rest in a wago box / in ceiling rose. This would...

Thanks @stem for your advice. I do have 1 radiator without a trv. The isolator would turn off the heating circuit. I think a 3port is probably the better way to go. Think I'm going to consult a plumber on this one as im sure they would complete such a task waay quicker than i would!

Ive had a quick look at 3 port valves and unless i am mistaken, it would appear the pipes would need to be rejigged to fit one since the inlet is from the pump on the side of the T, whereas all the valves i have seen have the inlet from the bottom of the T. Would i be better off going for an s...

I wondered if it was a failed valve thing as there were scorch marks behind it as if it had failed but that could be from a previous object or a gas torch. Maybe you are more right in it being a filter!

Currently my central heating and hot water go on and off together. I have an old glow worm fuelsaver 40b boiler which i think is 30 years old. It has one inlet and 1 outlet port. The system appears to be a gravity fed system (cold water tank, heating header tank, hot water tank without...

Hi John, Thank you for such a detailed response. 5s was first mentioned by @ban-all-sheds earlier on. I believe it was in reference to the disconnection times in 411.3.2.2, 411.3.2.3 Table B6 of the OSG also refers to 0.1 to 5s disconnection times which I think are related to the MCB current...

Maybe i am mis understanding something. If you have a L-E fault, a significant increase in current occurs. The temperature of the cable will begin to rise, and will overheat and become damaged assuming no adequate protection mechanism is in place. But we have a B40 MCB and tested that the...

@eflmpudence - your comments above are not about something I wrote, but something @ban-all-sheds wrote several years ago. Since it was directly related I added a link, and copied the relevant post hoping @ban-all-sheds could clarify.

@ban-all-sheds - I was reading another post via google as I have forgotten to provision for my cooker hood, and spotted a rather dated post (2005) from you that fits with this same topic: https://www.diynot.com/diy/threads/powering-a-cooker-hood.25547/

The rough calc was to consider that the EFLI would be unlikely to be anywhere near that value considering the csa of the cable. Without performing any measurements it would likely be many times smaller, so the fault current would be many times higher. I also was skipping over the time/current...

Not quite. a ring final 2.5mm spur ref B is 24A 1.45x overcurrent is 34.8A which would trip the 32A MCB. The same cannot be said for 2.5mm spurred from a 40A circuit. Yes, I am trying to justify the proposed solution back against the regulations, but there are so many if, but, except, when...

Yes, bad example. I was trying to think up a way of plugging in too many devices and overrating the cable.

I hadn't considered it to be the equivalent to a spur from a ring final circuit. Fair point. Whilst it is not a branch, after the cable csa reduction it does say "no socket outlets."

Yes in a correctly designed and installed system, the fault impedance would be low enough to trip a 40A MCB. 230V/40A = 5.75ohms. This doesn't account for an over current condition that is between 24A and 40A ish. Or should I just assume that in future no-one would be daft enough to plug a...

Yes I suppose you could argue that the fuse being downstream is sufficient, and the cable being in a fixed installation is sufficiently protected, and of a short length but it would be ignoring 434.2.1 "shall be no branch circuits or socket outlets"

I think this is not permitted by 434.2.1 but an FCU before the socket would be permitted.

So i've extracted snippets of the regulations in an effort confirm some of the suggestions above. EFLImpudence suggestion does not meet 433.1.1(ii) and does not meet 433.1.1(iii). 2.5mm2 cable Ref Method B = 24A. * 1.45 = 34.8A. MCB = 40A 433.3 doesn't apply here. 433.2.2 does...

0.79kW oven 0.88kW oven + fan 1.5kW grill. (Missed that one) If I connect 2.5mm from CCU to socket, what about the potential fault protection for the cable itself?

I am trying to decide what is the best / neatest way of rewiring my electric hob 6.6kW and electric oven 1kW. Oven is fitted with a 13A plug. Current wiring is 10mm from 40A fuse, to 45A isolator switch to JB (which i cant access due to kitchen cupboard) spurred 3 ways, 1. To JB connecting...