Dedicated mains setup quote advice

hi all

finally got chance from SWMBO to get an electrician round to quote for dedicated mains as finally got way forward of kicking the kids out of my soon to be listening room

in terms of having spent a long time trawling forum just wanted to get advice on what to ask the electrician to quote for set up wise - the work will all be done by qualified electrician

looking at naim manual was planning on asking electrician for a new dedicated MK sentry MCU, with a 32A type C then a single spur of 10mm double screened spur cable to a single furutech NCF socket.

in terms of earth remember seeing somewhere that should ask earth to be taken from before the main MCU via henley block

are there any other pointers i have missed that i should ask for in my quote ?

thanks again


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Your homework gets full marks, remember to respond with the resultant SQ. out of interest are you doing this for Humming equipment or just SQ?


Hi, you seem to be thinking along the right lines. I never bothered with screened cable, just regular 10mm T&E and an unswitched MK socket (not that these are anything special now that they are made in the Far East, but they work).
The important thing is to use a Henley Block or similar to split the meter tails rather than feeding the dedicated consumer unit from a spare slot on the main one, either of which are common practice amongst electricians. The earth cable should go to the earth connection near the meter, which often has a connector block with spare slots in it. Again, make sure your sparky doesn’t run this into the main consumer unit just for convenience.

Your biggest challenge might be finding an electrician who doesn’t think you’re stark raving mad, and will try to talk you into cutting corners on the basis that you are wasting your time. You might get lucky, but be prepared to shop around and avoid using someone who only reluctantly agrees to do it the way you’re asking.

Obviously the installation has to conform to current safety regs. Even these are open to a certain amount of interpretation but as long as the work is correctly signed off by a qualified electrician you should be fine.


is purely for SQ reasons have a smaller airlink balanced transformer between my current wall socket and wireworld matrix 2 and was astonished at the difference that made, so been big believer in good power supply from root-branch ever since (just never had chance to sort mains before)


thanks was bit fuzzy on the henley block bit will have to investigate meter to find the earth cable now :slight_smile:

tempted to pay bit more for some double screened 10mm spur from MCRU just so i sleep better… :grimacing:

thought single socket just for ease of install and not have to try and fit another 10mm cable into the back box



understand now found this image and can see meter has a spare way for another earth cable

oh well will find out if 1st spark willing to quote to do it this thurs

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I was lucky enough to be able to spec this for my new build with the developer.

Could I ask you just to research the difference between a spur circuit and a radial circuit? Using the Henley Block there should be no question of the electrician getting it wrong, but you never know!

Other members may help, but I think it’s a radial that is required.

Electricians may just do what is asked of them!



PS I’ve just seen the diagram, Radial it is! I’ll get my coat.

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Hi I installed a 6mm ring main running in parallel to the meter. A ring main will double the current capability of the circuit. The impedance will be lower than a single spur. If you lower your impedance it should help with a better treble and bass sound. A 10mm cable is dificult to fit into back of a socket a double socket un switched is what I used for my ring main. I would love to have a balanced mains unit as mentioned. Good Luck.


I have installed a few installations over the years and always run a 4mm ring main. This way each socket on the ring will have the same/ very close differential to the CCU ( fuse board ) keeping as close to the Naim start earching system as possible. ( Radial would be perfect but realistically your never going to get the reading’s the same at each socket )
Also two 4mm cables will fit into a crabtree or MK unswitched socket outlet two 10mm won’t. I also use a 32amp tyce c MCB as most of not all MCBs have the same size contacts just with different fault tolerances so no point in going for a 40amp or 45amp MCB.
And finally I always run the CPC back to the CCU and not to a separate Henley block. The resistance between the two will be almost nothing at all and as most supplies in the UK are TNC-S in the road even if they look like TNS in the property it’s a very good idea to keep the CPC the same length as the live conductors even if your using twin and earch cable and the CPC is 1.67 times smaller than the live conductors.
Finally using singles would give you the advantage of using the same size CPC and live conductors so 8mm earth total instead of 5mm total.

Can of worms completely smashed open now but as an NIC registered spark if I walked in a house with a 4mm ring I would be happy but with separate CPCs running of all over the place I would have a few questions and concerns even though all other options are all completely safe.


Can someone post the equivalent diagram for an installation in France as it one of my long term projects? A version in French would be even better!

Agreed, often misunderstood, by the ‘bigger is better’ brigade.


I installed 4 x 10mm T&E runs to get a more open detailed presentation…ducks down behind sofa :slight_smile:

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I have a silver plated gareage consumer unit from tm3 connections running my equipment via a 10mm cable to unswitched mk double socket. The mains are split via henly block on incoming feed to mcu.

Best vfm upgrade ive ever done. Electrician understood why i was doing it althpugh he did swear a few times getting the tails to fit in tbe socket.

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checked MCRU they have the 10mm cable in stock, guy laughed when i said was a 25m run to the hifi

not sure sparky will manage it will find out tomorrow they also had 6mm double shielded cable which would be my fall back

find out tomorrow will have a tempt the sparky with a covid secure kitkat or something :innocent:

Good luck! Sparky’s are a unique bunch :slight_smile:

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Not giving electrician’s stick, my brother’s one. My personal experience is they do like to talk! :rofl: :slightly_smiling_face: :joy:

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I showed this to my Electrician when I had mine done. The only difference being, that I had three runs of 6mm2 T&E.

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What specifically are you using? What difference did it make? Was it put in place to fix a particular problem?


I’ve got a radial circuit on a 16amp MCB then 4mm T & E going into 2 double unswitched MK silver plated sockets.

The two 135s are plugged direct to the mains sockets as is the 555PS. Then a Wireworld Matrix 2 is plugged into the other mains socket. The XPS2, Supercap 2, Lingo 1 , NAS Zoneripper and Phono stage are plugged into the Wireworld Matrix 2.

I keep my system on all the time. The only time I get problems is when I turn the system back on after turning if off due to current rush mainly from the Supercap 2 which has a large transformer.

Will change the MCB to type C and 20amps. In retrospect if I had the knowledge I have now would have gone for 2 separate radials 10mm cable.

Anyway, it sounds very very good.

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quick update after the sparky visit :slight_smile:

after he got over the initial shock :grimacing: that he had some raving lunatic going on about how sensitive his hifi was and why it needed a cable bigger than 4mm…

worked out only way to do it would be to route the cable external to house to get to the hifi

explained that wanted hifi CU prior to existing CU and earth close to meter as possible (he got there on the 5th iteration of my nudging…) and that CU needed a 32Amp type C MCB

cable wise is going to price for 4mm, 6mm and 10mm armoured and SY (double shielded) both which he said would be suitable for outside run as would be mounted, leaning towards shielded version for screening but will wait till i see price

only question he asked was whether the CU have a preference for RCD type? or have people just used normal/std one? (i had no idea this was a thing, but he said is there are different types of RCD a/b/c)?

anyhow thought would check and let sparky know and give a bit of an update as it looks as though its on :blush:

i just now need to order the furutech socket so he can check 10mm cable fits then can get it booked in for a 2/3 weeks time

as ever all this is being done by a qualified electrician