Dedicated Radial Plan

Is that MCG box your HiFi CU?

My box is almost full already.

In my box is that the incoming feed and breaker on the right, the meter top left, and the Earth wire bottom left?

Not sure there’s room for another CU in it, which is why I thought it would have to go in the sitting room.

Or could a very small CU be fitted in the top right hand corner of the box?

I don’t think it will fit in there! You would need a bigger box - or another box on the outside wall, or you can run tails to an internal location although there are restrictions on the length and routing of the tails. I’m sure your electrician will be able to advise.

1 Like

Yes - so ideally another small box containing a HiFi CU on the outside wall, with an armoured cable running in through the wall to supply the unswitched sockets behind the racks.

Right now this is what the inside room looks like, minus the gas fire that I took out:

That hole in the breeze blocks where the fire was goes all the way to the outside.

The plasterer is (hopefully) coming tomorrow to remove the plasterboard chimney breast and make the wall flat.

My electrician cannot come tomorrow, so I’m planning to leave the electricity cable that supplied the gas fire ignition coming out of the wall above the skirting board so it can be used to make a ring main socket of the TV/STB.

I think that would be ideal, although perhaps a bit of an eyesore. If there’s a suitable location on the other side of the wall that might be preferable.

It would be an eyesore, but rarely does a human eye look there as there’s not a path down that side of the house and it’s not visible from elsewhere (shrouded by large man-eating plants).

Yes, the MCG box is my Hifi CU.

Yours looks a tight fit unless something can be done about the unit on the right which is slapped right in the middle.

1 Like

Hi James, does the absence of the RCD make much difference SQ wise? Would this be allowed now?


Hi Phil - I suspect there would be very little difference but I didn’t compare both options. As I could have non RCD (subject to following some specific install conditions) i went that route. It’s prohibited now for domestic installs in the 18th edition regs.


1 Like

Thanks James. Is 100mA RCD allowed? We are gearing up for Solar with Powerwall and EV in the garage so third CU being added for all that stuff (already have the Henley. The HiFi will be added to its own CU. Mind you the system sounds mighty fine already with 4mm CY (shielded with 4mm earth as well) but there is no slack to allow the cable to be moved, so 10mm here we come! I’m guessing extensions wires are no good for HiFi.


I’m not sure Phil - I thought a 100mA RCD was not allowed in a domestic installation. 30mA is the rating needed for personal protection.

Your Electrician is best placed to advise here.

1 Like

100ma is the utility company rated fuse size for the whole house.

Also my opinion is that there is no point worrying about whether a 32ma RCD for your hifi supply is too low if your mains block feeder cable to wall socket is fitted with a 13amp fuse.

The utility fuse is usually 100A. The 100mA Phil referred to in the RCD spec is the amount of leakage current allowed before the RCD trips.


Got it James. I misread. Although I stand by the principle of the second paragraph of my post. That’s a real resistance bottle neck IMO.

The raison d,etre for a dedicated hifi supply is surely to isolate our hifi from the rest of our house supply for obvious reasons. Although ultimately we are the slave of what the utility company feed us with.

1 Like

A jaw dropping story was told to me by a hifi friend who visited me when I owned an Audio Note system. He told me that a certain dealer based in the midlands had fitted him a cooker wall socket which was fed from a 32a circuit breaker/6mm cable dedicated supply with his mains block wired directly into it. Some risk!

1 Like

Can I ask why you would want it removed, as it seems to be working, and presumably provides security for your Naim gear?