No sign of the missing post surfacing, or any news on why it went west, so....
wishy said:
As you have probably guesed I am no electrician, or anywhere close!
And I am very new to this Forum, but I must say how grateful I am for the help so far. Reading some posts has already enlightened me greatly.
I intend to install the circuits for both downstairs, upstairs, conservatory, and garden shed supply on individual NSB32 MCB on the RCD (80A/30mA)side. I also have a seperate kitchen ring main and Smeg A2 gas hob with electric double oven cooker connected on the RCD side both using the same rating of MCB's.
This means there would be six 32A MCB's on the RCD side filling all available connections.
IS THIS TOO MUCH!!?
It's a bit steep. Even allowing for the fact that your shed cannot be on a 32A breaker, (as I said before, 20A would be the max), I make that, applying the generic diversity guidelines, just over 100A. Diversity is the concept that not all circuits will be loaded to their maximum simultaneously, and that you therefore make certain assumptions about how much load to allow for each circuit when assessing the total requirement. These "assumptions" are not a substitute for proper design, so if you were doing something out of the ordinary - e.g. you take in washing so in the utility room there are 2 washing machines, a tumble drier and an iron on continually all day, then the assumptions would not be valid, but in the absence of any particular knowledge, the wiring regs has a table of assumptions you can use. So if you had 6 x 32A socket circuits, you'd count 1 at 32A and the rest at 40%, making 96A. You can read more about this
here .
I made yours more than that because one of your circuits supplies a cooking appliance, and there is a different calculation for that, but I had to assume that the appliance rating is the full 32A, or thereabouts (which it probably isn't), and that the cooker control unit has a socket (which it may not), making that circuit 21A.
So 4 socket circuits at 32A, plus 1 at 20A (shed), plus the cooker = 101.4A.
There are things you can do to get this figure down. You can run the shed from a 15/16A breaker. You can look at what your oven really draws (I doubt it's 7kW), and fit a lower rated breaker. You will struggle to get it down to below 80A though, so you may have to move a circuit to the non-RCD side.
Above the RCD are the lighting circuits, alarm, door bell and the new conservatory lighting supply cable, which I now appreciate needs to go through a NSB16 MCB
NO - this is too big for a lighting circuit - 10A max.
The SWA is 10m long 2.5 3 core connected via a 32 amp junction box indoors to 10 m 2.5 cable running to the CU.
Unless the 2.5mm cable indoors is buried in an insulated wall then you'd be OK for 20A.
Already purchased a double weatherproof socket for shed, without RCD. Drat!
Well - if you have to change it you have to change it, that's all there is.
I would strongly suggest you do a search here for words like shed, garage, outside, outbuilding, outhouse etc for fuller advice on best practices concerning the supply of electricity to the shed.
