Dedicated Radial Circuit Query

We are having some work done on our house and this presents a good opportunity to install a dedicated radial. I have read the numerous threads on this subject, in particular the extensive one from last year.

Using the schematic drawing posted a while back (by, I think @james_n ) I have consulted with a few electricians. To be honest, I was on the verge of giving up on this idea as none of them filled me with any confidence. Anyway, I have finally found an electrician who seems knowledgable and up for the job.

Given the locations of the existing CU and where I need the sockets installing, it seems the best option is to run armoured cable externally from the new CU to the new sockets. This will mean a cable run of around 35 metres. From reading previous threads, I think other forum members may have done something similar, but I was wondering if there are any downsides to running such a long length of cable externally?

The only other query I have is the electrician asked why a 32A Type C MCB was required (as per the schematic drawing)? He seemed to think 32A was a bit over the top.

I am not at all technically minded, so any help on these questions would be gratefully received.

None at all mine runs externally and works fine.

Can’t answer the other question sorry.

I believe Type C deals with inrush current better… Rather than that standard Type B…

Just checked my Consumer Unit - all are Type B…

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I had a separate CU installed along with a dedicated spur and it originally had Type B. 90% of the time it would trip when powering on a unit with a big PSU (e.g. NAP300).

Had to get it changed to a type C and all has worked fine since then.

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Thanks Lindsay - that’s good to know.

Thanks Ian.

Thanks Graham - type C seems the way to go.

Type C prevents accidental tripping when you turn on Naim boxes with large toroidal PSUs due to the large inrush current. Definitely recommended, my system used to trip most times I turned it on, until I put in a Type C, then it never happened again.
When Steve Hopkins was at Naim he recommended a 32 Amp breaker for my system at the time, which was NDX/282/200DR, so not overkill for yours.

Mine will be installed in just over 2 weeks. I assume you will be using 10mm SWA. This is what I will be using and he is ordering 40 meters to go up one side of the house, through the loft, and out the other side, then down to the living room.

Someone also suggested getting the 10KV RCBO(or MCB) rather than the standard 6KV, which should have a bigger contacts. I’ve mentioned this to a couple of electricians, and they don’t seem to have any view on it either way, so I’m going that route.

I think the thing here is that the electrician will ensure the installation is fit for purpose and meets all the regs, so whilst they may not fully understand, it shouldn’t really matter.

Boring reply, but same here

Thanks Chris. From reading other threads, I thought it might be for the reasons you have outlined, but your clear explanation will enable me to pass this on to the electrician.

Thanks @GadgetMan - yes, 10mm. Thanks for the additional information.

Thanks - type C it is.

Some electricians have a rather narrow and rigid interpretation of the regs. There is endless discussion amongst them about how exactly many of the regs should be interpreted. Obviously you will need yours to certify the installation, but if he looks at you like you’re a nut case and agrees to do what you want anyway, I would find a different sparky.

I got a good impression of the electrician I saw this morning (not least because he seemed to fully understand the schematic drawing) unlike the others who either didn’t seem to understand or wanted to do things their own way.

The first two I tried were just too busy to take on the work (or were scared when I gave them detail). Third one came to the house, and I was confident after a chat. In the end they are not doing anything different to what they do most days.

Also availability is becoming an issue for some stuff, so get it in while you can

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