Dedicated Mains - Some Pictures
Posted by: DaveBk on 21 February 2009
In recent months there has been quite alot of interest in dedicated hifi mains circuits. Many people have asked what is involved so I thought I would post a few pictures to explain what I have done:
This shows the new hifi consumer unit. It's fed directly from the incoming mains using 25mm power conductors and a 16mm earth. Two 32 Amp circuit breakers feed the 6mm and 10mm radials.
This shows the 2 radial circuits crossing the loft before heading down the wall buried in the plaster.
And this shows the final socket outlets on the wall. The switched one is a spur off the upstairs ring that is used for the Sky box and DVD player. Next is an unswitched double where the 6mm radial terminates - this powers the NAP300 in my case. Next to this is the 10mm radial again terminated with a MK unswitched socket powering the Supercap for the NAC252 and the Transporter. The Transporter is modified to replace its switched power supply for the digital side with a linear unit of my own design so no nasty RF gets back onto the radial.
Finally an picture showing one of the measurable benefits of dedicated radials. The meter is an earth loop tester - it measures the resistance of the whole circuit from the local substation to the socket via the live and back to the earth. (Earth and Neutral are usually joined in the cut-out where the mains enters your house) Generally speaking the lower the resistance the better. The meters are shown in the same order as the sockets so it can be seen that the 10mm radial has the lowest earth resistance - low resistance return paths to earth are important in my experiance with high end hifi.
The only place in my setup where the mains earth is connected to signal earth in in the Transporter, this should be connected to the 'stiffest' earth so I use the 10mm radial. I also power the Supercap from here to keep it away from the 300PS.
So this wraps it up, not forgetting of course the 3 Powerlines from the sockets to the kit.
Posted on: 21 February 2009 by spacey
good job, i have a similar setup, well worth it. one of the best upgrades for any hifi.
Posted on: 21 February 2009 by David Leedham
Very interesting Dave. did you have this installed in a new build?, DIY? or with the assistance of a sparky?
Posted on: 21 February 2009 by DaveBk
quote:
Very interesting Dave. did you have this installed in a new build?, DIY? or with the assistance of a sparky?
DIY, but knowledgable DIY. I have a background in electronic engineering and also did a complete replacement of the main consumer unit and kitchen ring in my house a while back with the local building control reviewing every stage.
Posted on: 21 February 2009 by DaveBk
Munch, why? Last time I checked the regs the only restriction was when the cables are either tightly bundled, or running through an insulating material?
Posted on: 21 February 2009 by Consciousmess
Dave,
Many thanks for these pictures as I am in the process now of starting to get the job done. I will have an electrician around soon and the cables will be under my floorboards.
I was originally troubled that a lot of disruption would occur, but as one of the floorboards in the lounge needs replacing (due to wood worm I think), I'm using that opportunity to get the new spur.
Thanks again for the pictures and I now have 3 Powerlines so my system will be similar to yours (as I see you have 252+300).
Regards,
Jon
Posted on: 21 February 2009 by Adam Meredith
Please confirm that you complied with all regulations (that is those that might require the work to be inspected and signed off) vis-a-vis this installation or I will remove this thread.
Posted on: 21 February 2009 by DaveBk
Adam, I confirm that all necessary regulations were confirmed to that applied in early 2008. The new regs which came into force in mid 2008 (17th Edition) do require RCDs in all circuits.
I do however disagree with Munch's view that cables now need to be protected from chewing through, but generally I do not condone non standard electrical work. Happy for the thread to be locked or deleted if you feel this is an inappropriate discussion.
Posted on: 22 February 2009 by DaveBk
With hindsite I can see the concern over posting details of electrical instalations on this forum. I've therefore removed the offending images and left only those that illustrate the point I wanted to make - that there are measurable reasons why a separate radial should be competantly installed.
Posted on: 22 February 2009 by neil w
quote:
Originally posted by munch:
Had my sparks round three weeks ago to sort mine out.
So i know what i am talking about.
Munch
i work on new build , and have never seen the practice your'e on about
Posted on: 22 February 2009 by spacey
quote:
Originally posted by munch:
Had my sparks round three weeks ago to sort mine out.
So i know what i am talking about.
Munch
munch your sparks not right. you need trunking if you putting the cables into masonary plasterd walls but you can install cables in voids without. i have never seen surface mounted cables around a CU trucked have you? the safety issue is people drilling through the cables when fixing to walls etc.
Posted on: 22 February 2009 by Consciousmess
This is an interesting thread, and I have an electrian due round this week to quote me on the spur.
Now I am expecting 200-300 to be the figure but upon reading this thread and the other thread present in the 'Padded Cell', this guy is going to have to pull the carpet up for half the room and thread the new cables under the floorboards, followed by attaching 4 sockets next to my hifi.
I suppose I could move the furniture and pull the carpet up myself, but does the sparky provide all the necessary materials along with the quote - i.e. cables, plugs, miscellaneous electrical bits?
Would I be required to buy this stuff first, and if so, what are the items and what thickness do I need for optimum benefit?
Many thanks,
Jon
Posted on: 22 February 2009 by 555
I think you'll get the answers from your sparky when s/he visits Jon.
Make sure you have a list of questions & specifications,
so you don't forget anything on the big day.
Posted on: 22 February 2009 by spacey
quote:
Originally posted by Consciousmess:
This is an interesting thread, and I have an electrian due round this week to quote me on the spur.
Now I am expecting 200-300 to be the figure but upon reading this thread and the other thread present in the 'Padded Cell', this guy is going to have to pull the carpet up for half the room and thread the new cables under the floorboards, followed by attaching 4 sockets next to my hifi.
I suppose I could move the furniture and pull the carpet up myself, but does the sparky provide all the necessary materials along with the quote - i.e. cables, plugs, miscellaneous electrical bits?
Would I be required to buy this stuff first, and if so, what are the items and what thickness do I need for optimum benefit?
Many thanks,
Jon
my 2p's worth; get a 10mm.sq spur fitted with MK parts throughout. make sure he/she doesnt cut any corners and is fully approved to do the job. ask to see there appoval certificate before they commence. its vital for home insurance these days.
Posted on: 23 February 2009 by count.d
Jon,
When your electrician comes, make sure he connects the two distribution blocks like "B". Both are acceptable electrical connections, but for a hifi, I've found that "A" is terrible.
It probably seems obvious looking at the drawing which is best, but electricians don't think in hifi terms.
Posted on: 24 February 2009 by DaveBk
Good diagram - and I agree!
Posted on: 24 February 2009 by 'haroldbudd'
good thread, thanx Dave.
Posted on: 24 February 2009 by 555
Threads can come back from the dead count.d!
Posted on: 24 February 2009 by count.d
Cheers Adam.
quote:
Threads can come back from the dead count.d!
Which reminds me, when are you coming for a quick bite 555?
Posted on: 25 February 2009 by 555
Posted on: 28 February 2009 by Consciousmess
Hi all,
At last my electrician is due round tomorrow to give me the quote. I have noted that I need to get a 10mm square spur and will insist on this, but what will happen is I want him to fit two double plug sockets on the wall next to my hifi, so I have all my components (3 of them) in their individual sockets, with a spare socket if I were to get an nVi in the future or an nSUB.
Can I just ask first though, would these two double sockets come off ONE 10mm spur (which equals a 10mm cable?) or do I need two 10mm spurs, one for each double socket?
Sorry for these questions, but I want to have a little bit of knowledge before the electrician comes round!!
Jon
Posted on: 28 February 2009 by DaveBk
Jon, there are 2 schools of thought here. One would suggest a single spur feeding both sockets is best, but this can be difficult in practice due to having to squeeze 2 thick cables into the screw connectors on the back of the socket. 10mm squared conductors have an outside diameter of about 4mm which is about as thick as most sockets can take. I use 2 spurs each feeding a double socket as I beleive this to be easier and better to wire up properly. The perceived disadvantage of this approach is 2 earth paths, but as only the cd player connects signal earth to mains earth I do not beleive this to be bad. The other earth wire is only connected to the equipment chassis so plays no part in the audio earthing arrangements.
Posted on: 01 March 2009 by Consciousmess
Dave,
Thanks for those tips and I have to say that the electrician has just been round. He's taken away my requirements on a piece of paper and is getting back to me ASAP with a quote.
Now, he asked about this 10mm conductor and I said it had to be 10mm as I wanted the best connection to my hi-fi sockets.
He then said to me that he may need to use FOUR 10mm spurs feeding the 4 sockets. I understand your point about the signal earth as it only connects to the CD player, but would I interfere with the 'ideal' separate spur situation many of us want to achieve with our audio components?
Apologies for this question, but I am naive when it comes to electrical issues and I am relying og the forum guidance!
Many thanks,
Jon
Posted on: 01 March 2009 by DaveBk
There's no easy answer Jon. As I said, 2 schools of thought. ken c and I were just having this very debate about distribution blocks in hifi corner. The only option could be to try both options, listen and trust your ears.
Posted on: 05 March 2009 by Consciousmess
Hiya,
I've just got the quote back from the first electrician and I would be grateful if anyone could give some guidance:
The electrician has written:
Supply and fit 30ma RCD protected consumer unit next to consumer unit
Is that what I need for a dedicated hifi spur? Part of me questions why he put 30ma??
Run 4 x radial circuits in 10mm to 4 separate souble sockets in lounge
This will need clarifying as I did specify 2 separate double sockets (thus TWO 10mm radial circuits).
Total cost= £338.27
I'd be really grateful for any of your help!
Regards,
Jon
Posted on: 05 March 2009 by DaveBk
Jon,
Latest regs say all sockets need to be protected by an RCD. 30mA is the maximum leakage current to earth that they will allow before they trip - this is set to be below what would kill you if you were unfortunate enough to become part of the circuit!
The old regs before mid 2008 used to say that only sockets that were likely to be used for outside equipment needed to be protected by an RCD - this was typically interpreted as any downstairs.
it is possible to have non RCD protected circuits for some special purposes, but any buried cables need to be in earthed steel conduit to protect against people drilling or nailing into walls.
The price seems reasonable, but make sure he's registered with NICEIC or some other approved body, or you will still need local building control to approve the work.
