10mm dedicated mains supply, but is a separate CU really necessary?

O wow , very reasonable
Thanks for that :+1:

Look on some of the sites like Screw-Fix and other electrical providers for CUs, cables, RCBOs – noting a good sparks should be able to bet minor discounts for ‘trade’ from some places.

The primary cost is the labour IME.

Compared to the cost of some boxes, it’s a snip :grin:

It was an easy peasy one as the small room with meter in is behind the listening room……
just drilled through the wall and the socket and CU are literally back to back. It took him 20 minutes at most.

Mine was just under £700, but that included 40 meters of Steel Wired Armoured cable - very reasonable I thought

@DJM for the earth supply to the new CU, you ideally want to go back to where the earth comes in. In some cases there might be a separate earth block used for earth, but if you can go back to the incoming earth, then all the better.

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You just need to ensure that the earth cable, as well as the live and neutral, are connected straight back to the connection points near the meter. Not via the main consumer unit. Just worth mentioning to your electrician in case he earths via the main CU which he might possibly do for convenience.

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I don’t think a dedicated CU & feed can cure the toroid hum (at least, don’t expect it to), as this stems primarily from incoming mains contamination (voltage and cycle issues), which can come and go like the weather!

If you are considering doing this, one thing which helps is to see the best route for cabling (access et al) and where you want the socket(s). It helps to know how your house has been built e.g. many years back, new-builds had cable conduits sunk in the concrete floors. Of course, many pre/inter-war houses, have suspended floors. Cavity walls can help.

As @Gazza points out, simply coming through a wall from where the meter/feed/existing CU is located is straightforward – having to traverse across a house and/or run a cable externally, is where the labour costs add up, as can the domestic disturbance.

I live in a fairly new house (early 80’s)
Main issue would be routing the cable , meter and hifi couldn’t be futher away :man_facepalming:
Possibly have to run external all weather cable clipped outside
Any thoughts??

And sorry absolutely no intention of hijacking this thread ,
sorry again to DJM

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I ran my 10mm SWA cable out of my garage, up the wall, through the loft, and down the other wall - 40 meters in all.

Suggestions –

1- run armoured cable around the outside – which can be buried and/or in an external conduit laterally/vertically (see on). There are pics on here of some having done this in relative new-builds. I think armoured is required for underground runs (which should be a min. certain depth) and you may be OK with ordinary cable in metal conduit.

You can pin armoured to an external wall but with a long run (if allowed under regs?) conduit would look neater IMHO.

You’ll need to check with sparky – I’m not sure if you chose the conduit route, whether it will need to have armoured inside (I think not).

2- check outside and see if you can access roof-space for an ‘up & over’ (in loft/roofspace or even above/behind any soffit boards).

While external conduit may look a tad unsightly (but can be disguised a tad), the alternatives can be far worse.

I’m guessing that as an '80s build you have sold concrete floors? (and maybe even underfloor heating).

3- the meter location plays if running external (i.e. you can T-off from there) but where is the house CU, as the route from this may be easier?

You may be able to split the mains feed at the existing CU?..assuming you have room for another CU and the bits and bobs.

CU and meter are in single story garage which is attached to house
cable up to roof of garage into main house
All mains wiring then under second floor dropping down for first floor , up for bedrooms etc
Don’t fancy idea of all flooring up to get to far side of house , SWMBO would have kittens
Time to contact a sparky i think :zap:
Thanks all :heart_eyes:

This is a good thread to read, being @JimDog 's project – and at post #17(ish) you can see @ChrisSU 's external conduit.

Suggest start your own thread – especially if sparky pushes back on suggestions, thinks you need the men in white coats!

Thanks for explaining that👍

Hum is most often caused by over voltage and secondly by DC offset. Though for some inexplicable reasons audiophiles are always obsessed with thinking it’s DC offset.

Have you had the voltage coming into the house measured? If it is over, the electric company can be informed. Not sure about the UK but here, they can tune what’s coming in up or down about 3v out at the transformer on the utility pole.

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That sounds simple enough. Thanks

Did you use a Henley Block to split the tails? If so, have you got a photo?

Thanks👍

The Henley block is the box at the top right

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Thanks James😀

To the OP, be glad you have a typical skeptical sparky.

My house build is a month behind schedule becsuse my electrician and his boss (a big Tokyo based electrical engineering firm) are huge audiophiles and decided to “extrapolate and take initiative” on my simple request for one audio CU, one audio earth rod and 8mm cable on obe circuit. I got handed plans and a $100k bill just 2 weeks before the start of wiring that used silver core mains wire. A separate earth rod and CU for every single circuit (so about 8 independent earths!) . EM shielded
trunking conduits; the works. I sacked them (you just don’t take “initiative” to spend a customers money right before a build) but couldn’t find a sparky who can start a big job this year. So had to back to the audiophile sparky and now I’m micromanaging every wall plate, every drum of cable, every conduit. All because the sparky thought he’d found a kindred spirit.

Lesson: pushback from a sparky that doesn’t understand this stuff is fine. It’s the ones who do know mains makes a difference are the ones you want to worry about :rofl:

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I have followed this (and other) thread with interest.

My sparky (UK) has just left after I asked him to look at installing a dedicated mains for the hifi.

I showed him the diagram and a number of posts about what I would like. He called his inspector as he had never heard of installing 10mm2 cable into a double un-switched socket! Neither had the inspector🙄

We left it that he was going to his workshop to see if it is straightforward to wire a 10mm2 cable to a socket…if so we are good to go otherwise he is going to recommend 6mm2 which I’m not overly keen on unless I have misunderstood the optimal solution.

Is there anything that I could suggest to him to make said wiring to the socket should it be an issue?