Is this CU right

Apart from waiting for dennis to tell you that 32A 2.5mm T&E final ring circuits are the devils spunk I would say you are looking in good order to install.

A load of bollocks here for you to read and forget

Fridge and freezer on a none RCD circuit, to avoid food spoiling if there is an RCD tripped in your absence?

"a relatively low-priced and widely available safety item"

low priced??

And isn't there a bit of a fire risk having something that goes pftttt in a consumer unit? In the top photo it's wired across the main switch and not even fused down

Owain

like many (most?) such it comes built in fuses so needs no additional overcurrent protection.

ahem...except on (still not sober) reflection & checking that seems to be one that does require external overcurrent protection

Tricky unless you use SWA or pay a lot of detail to the cable route.

A 7kW shower is ok but many installs suggest 6mm. The voltage drop at

It's a CU swap not a rewire.

Strictly speaking all sockets should now be RCD protected inducing the ones in the OP's loft.

Type 1 and 2 SPDs are fitted at the origin and need no further overcurrent protection.

Although BG do seem to have a typo right at the bottom (in the safety warning)

OK that is one "gotcha", I did not realise all sockets were to be RCD protected I thought it only applied those with wiring less than 50mm deep in the walls.

Just to clarify the alarm situation. When we first moved in the so called professionally installed alarm was useless. As a temporary measure because we knew the kitchen and bathroom were going to be re-done resulting in quite a lot of disruption and rewiring of the kitchen. I was loathe to start any work that involved major disruption until I had to. The system we bought was a wireless DIY system this meant that the control box and bell boxes each had their own wall wart PSUs. As a temporary measure and to keep the PSUs out of sight and out of mind sockets were located in a convenient place in the loft. These sockets were for convenience sake only for the alarm and wired into the light circuit which was not RCD protected a little naughty but the alarm at best draws minimum current about 200mA if I recall. The CU does not have any spare ways so there was not really much else that could be done at the time.

As well as the CU swap I am doing a partial rewire mainly the kitchen and separating the lighting circuit into two as described above and connecting the garage. The kitchen ring main will be completely new as at present all the sockets are in the wrong places with most of the if not replaced would end up above the middle of the hob along with several fixed appliance switches. Other rewiring involves putting the alarm sockets on a separate circuit instead of the lighting circuit and also the boiler which is in the airing cupboard and utilises the old immersion circuit, a fused spur unit in the cupboard with the feed going via a switch in the kitchen situated above the new hob position, the plan with the latter is to eliminate the remote switch and feed directly from the CU. Whilst pulling through the cable for the boiler I can draw two cables through to the airing including the proposed alarm cable which will be surface mounted in the airing cupboard.

So not quite a full rewire but well on the way. As implied before the CU was replaced sometime before we bought the house utilising all the old circuits apart from wiring in the shower. This left a messy arrangement of junction boxes dangling off cables as a result of repositioning the CU higher. The rewire will eliminate the junction boxes as the new CU will be lower now that some of the clutter in the way is being removed.

Richard

That's me back in my rest state - i.e. confused :)

I'd got it in my head that SPDs needed overcurrent protection that discriminates from the main fuse. From my doodles on a possible new CU I seem to have got that from the page 49 of the BEAMA guide - but I see that is only "should", not "must".

Afraid so, even sockets fed from SWA or in trunking. However you could feed a RCD socket with SWA or truncked cable. The same now applies for lights in domestic properties.

Have you bought it yet?

Just I have spotted an alternative.

If you don't want that circuit to share an RCD with others, put it on an RCBO instead of MCB?

It seems some of them do require MCB protection.

You would think it should handle thousands of amps or its not going to do anything useful.

They can handle 10s of kA - but only for /very/ short periods.

The overcurrent protection is to protect the cables and SPD against faults.

The company fuse should protect those. Typically its 100A, mine is only 80A though. Obviously if the SPD you buy specifies less then you need something extra to protect it.

1. You may be happy to risk a faulty SPD taking out the "company fuse". Others wouldn't.
2. Some SPDs specify maximum overcurrent protection of less than 80A - including the one in photo (63A).