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Dedicated Mains (again)

J

jevy47

pfm Member
For a while I have been contemplating having a dedicated mains supply to my hifi.
In the next two weeks I will be fitting new cupboard space so this is the ideal time to trace cables.

So basically what do I need from mains board to hifi ?
The cable run will be 22m in total.
The budget will be no more than £300.

HiFi is LP12/Origin Live motor/tom Evans Microgroove+
Eikos CD player
Naim 82
Sonic Bliss psu
Naim 250 (Avondaled)
Linn Isobariks.

Any advice with type of cable and mains blocks etc would be greatfully received.

Cheers

Davey.
 
The only sensible answer is that you need an electrician as this work is notifiable to LABC under part P of the building regs.
You will require design calculations and test schedules with results.
 
Within that price range you could just about do a dedicated consumer unit, but if space is a constraint and you have space on your existing board to add a separate radial circuit that would be worth doing too. My personal recommendation would be a 20A or 32A radial - I think 17th ed. specifies a minimum 4mm for live and neutral and 2.5mm for earth - i.e. 4mm T&E, but I would use the largest T&E you can afford that will fit the sockets!

The type of protective device would be dictated by the existing installation, the electrician who fits for you should be able to advise and beyond stating a preference for something from the likes of MK or Crabtree etc. to give you a bit of peace of mind about the quality, I would just follow his or her advice. I would just add that I think the things you hear about the disadvantages of RCDs and RCBOs in hi-fi and especially Naim systems is largely a product of early designs and modern designs do not have the same issues.

My personal preference socket wise is the unswitched version of the MK Logic+, reputedly singles are better than doubles, but I have got on just fine with doubles!

I know with the Linn Lingo, splitting the TT PSU off on a separate radial again is popular option and one that makes a difference to my ears, but I have no idea whether that is sensible or not with the Origin Live Motor.
 
BS7671 (17th) does not specify a cable size for radial or ring final circuits. The size is obtained once calculations have been done for circuit length, installation method, expected load allowinig diversity etc. Then the cable size can be calculated. his all needs to be noted and final test results obtained.

The circuit will need a suitable means of ADS, again this is determined by installation method.

An RCD or RCBO is essential unless the cable is mechanicaly protected against impact etc.
 
penance said:
The only sensible answer is that you need an electrician as this work is notifiable to LABC under part P of the building regs.
You will require design calculations and test schedules with results.
Click to expand...

Actually, there is a way to do it yourself that is sometimes employed by house builders etc. but as it involves quite a bit of bureaucracy and the LA sending out an inspector; with the charges that entails it certainly wouldn't be remotely cost effective to do so for such a minor piece of work! The electrician will usually be attached to a trade body and be able to notify through them at a much lower cost.

The OP is still right to ask the question though, I don't think he was suggesting that he would do the work himself - I certainly didn't read it that way. There are 2 main ways of fitting dedicated extra sockets, as well as two main ways of adding more sockets to an existing circuit, lots of different sizes of cables that can be used within the regs etc. etc. - I took it as given that the OP would comply with the law, not to mention act in the safety interests of his family, but just because a part P registered installer can do the legal side of it doesn't mean that they necessarily know how best to tailor the installation for what is a somewhat esoteric application!
 
Our LABC charges around £300 for initial application and sign off. It costs me £2.50 to do the same via the sheme i belong too.
Sadly it is not law, BS7671 is not statutary, tho if anything did go wrong and you hadnt followed it.....
 
Many thinks for your replies.

The only work I would be doing is running the cable from the house RCD unit to my system.

I will supply the cable and sockets (which ones within budget).
I could maybe stretch my budget to £400 if there would be any real benefit in safety or SQ.

A qualified house spark would be doing the leccy stuff.
 
Are you running the Tom Evans Pulse with your Eikos?

Mains leads from Mark grant with or without Furutech connectors and either his mains block at £180 or if you want to splash out, the Music Works Ultra at £960.

Anthony Matthews, Tom's former business partner does a mains filter that works well in conjunction with the Eikos even with dedicated mains.
 
penance said:
BS7671 (17th) does not specify a cable size for radial or ring final circuits. The size is obtained once calculations have been done for circuit length, installation method, expected load allowinig diversity etc. Then the cable size can be calculated. his all needs to be noted and final test results obtained.
Click to expand...
I had always assumed that the values shown in the diagram on page 4 of this document were recommended minimum values and IME it has been what installers have used. There is, however, no reason not to use a cable of larger CSA than is necessary, and in hi-fi it is generally taken as given that the lowest mains impedance possible is good; which was my point - 4mm t&e is just what, IME an installer would just have run in as standard if asked to add a few sockets on their own radial.

I have never seen an installer doing any calculations for such a minor bit of work, they have all in my experience just used such rules of thumb, installed and then tested. I have however seen them pissing on earth spikes to get a lower earth impedance reading so that they could pass an installation, and on one occasion exploding a kettle because they had hooked it up straight to meter tails and left it turned on when they pushed the supply fuse back into place - because they wanted a cup of tea. So please excuse me if I don't exactly have the deference towards your profession you clearly think I should!

An RCD or RCBO is essential unless the cable is mechanicaly protected against impact etc.
Click to expand...
Again, I had said what I did for just this reason, the internet is full of "you must have a non RCD hi-fi circuit - it ruins the sound" nonsense. The point was to reassure him that he didn't need a non-RCD supply buried deep, run in SWA or through armoured conduit etc. etc. at much greater expense.
 
djftw said:
I had always assumed that the values shown in the diagram on page 4 of this document were recommended minimum values and IME it has been what installers have used. There is, however, no reason not to use a cable of larger CSA than is necessary, and in hi-fi it is generally taken as given that the lowest mains impedance possible is good; which was my point - 4mm t&e is just what, IME an installer would just have run in as standard if asked to add a few sockets on their own radial.

I have never seen an installer doing any calculations for such a minor bit of work, they have all in my experience just used such rules of thumb, installed and then tested. I have however seen them pissing on earth spikes to get a lower earth impedance reading so that they could pass an installation, and on one occasion exploding a kettle because they had hooked it up straight to meter tails and left it turned on when they pushed the supply fuse back into place - because they wanted a cup of tea. So please excuse me if I don't exactly have the deference towards your profession you clearly think I should!


Again, I had said what I did for just this reason, the internet is full of "you must have a non RCD hi-fi circuit - it ruins the sound" nonsense. The point was to reassure him that he didn't need a non-RCD supply buried deep, run in SWA or through armoured conduit etc. etc. at much greater expense.
Click to expand...

Not sure what document you linked to as it wont open.

Agree that in many situations standard accepted CSA is quite acceptable and safe, but BS7671 design criteria still say the relevant calculations are required.
Installation method in modern buildings is probably the most important as cable are much more likely to run in insulation of some kind thus reducing heat dissipation of the cable.
Also cable run legth will effect voltage drop and may require and increased CSA. Again this is part of the calculations required.
TBH the days of rule of thumb are gone now, whether for good or bad is another discussion.

You can have a non RCD protected circuit with the need for conduit or SWA if the cable is surface clipped.

The chap who attached the kettle to the tails, did he have a horse and stetson?
 
Thanks again for your replies.

Steven my Eikos has the analogue and digital internal board upgrade.
A Tom Evans Pulse .............some day maybe.
 
JEVY47 Are you contemplating just ONE radial circuit and using an existing (i.e. shared) consumer unit?

Having dedicated mains, the donkey work for which you can do yourself, is, i.m.o., so cost effective that you should have a more flexible budget, though £300 sounds just about feasible.

There are different ways to do it; ,Mister DOPPEL of this parish has his effected one way, I have a straightforward multi-cable system to a dedicated Memera c.u.
 
I ran a 35mm sq cable from incomer (In parallel to the existing house supply) with VERY big tails (Bigger than 50mm sq) to a dedicated consumer unit in the room, the fed each piece of equipment with a seperate line from the board using 6mm sq cable min from CU to equipment.

Thick but has moved the whole kit onto a different level in terms of solidity, weight and low noise floor. It's like it has a real foundation that it missed before.
 
penance said:
Not sure what document you linked to as it wont open.
Click to expand...

I can't understand why, it is working for me!

The document is "Requirements for Electrical Installations IEE Wiring Regulations, Seventeenth Edition BS 7671:2008 Corrigendum (July 2008)" and the diagram "Fig 15B RADIAL FINAL CIRCUIT ARRANGEMENTS, REGULATION 433.1"

Agree that in many situations standard accepted CSA is quite acceptable and safe, but BS7671 design criteria still say the relevant calculations are required.
Installation method in modern buildings is probably the most important as cable are much more likely to run in insulation of some kind thus reducing heat dissipation of the cable.
Also cable run legth will effect voltage drop and may require and increased CSA. Again this is part of the calculations required.
Click to expand...
I know that is what should happen, but in a domestic setting excepting a complete installation or rewire I have never seen it done - I'm sure it will do in large firms and commercial installations, but TBH I think demotivated has hit the nail on the head. Just to be clear - I think I already had made it clear, but just in case I was telling the OP to use the largest T&E that was practical and which he could afford.
TBH the days of rule of thumb are gone now, whether for good or bad is another discussion.
Click to expand...
I really don't think they are, some of the guys have been pretty young - apprenticeships obviously pass on bad habits as well as good.
You can have a non RCD protected circuit with the need for conduit or SWA if the cable is surface clipped.

The chap who attached the kettle to the tails, did he have a horse and stetson?
Click to expand...
No, it was two of them, in a nice new VW van done in company livery, it wasn't a company I recognised, but if they were cowboys they'd gone to impressive lengths to look legit. It was a client's house, so no idea really, but they both had NICEIC, or maybe NAPIT badges, same again and a City and Guilds logo on the van etc. etc. the client didn't strike me as the sort of man who wouldn't have checked - he was a very reputable property developer (in so far as they can be) and I'd have though would have known the difference between "Part P Certified" and "actual electrician". Though again they were quite young, the younger could have been an apprentice, maybe just reckless rather than lacking knowledge - I don't think they'd do it again from the way they looked after!
 
Mike the idea was to run only one radial circuit on a shared consumer unit, but reading the comments I think it will be better to bite the bullet and install 2 or 3 with a dedicated consumer unit.

Would there be much difference with say 3 compared to one ?

Cheers

Davey
 
The received wisdom is that Naim kit should all go on one, unless every component is on an individual radial - I think the idea is to get as close to a star-earthing arrangement as possible. As I said earlier I have heard the benefits of putting a Lingo on a separate radial - I don't know if this would be of benefit with the OL DC, but it certainly can't hurt. Beyond that it is rather hard to say, I'm not especially familiar with some of your other components - I would be inclined to put every thing that is part of the analogue circuitry on one radial.
 
jevy47 said:
Mike the idea was to run only one radial circuit on a shared consumer unit, but reading the comments I think it will be better to bite the bullet and install 2 or 3 with a dedicated consumer unit.

Would there be much difference with say 3 compared to one ?

Cheers

Davey
Click to expand...

No bullet to bite, I feel. If you're going to keep your house, your hifi and upgrade from time to time, it's surely worth the peace of mind to know that the most important source of all is the best you can sensibly have.

As aforesaid, if you do the donkey work by routing the cables; even installing and connecting the single sockets (if that's what you want to use (I don't use any)), you only pay for the parts and the sparks to do the final c.u.connections, junction box and tails, main 100amp fuse (if not in situ).

Parts are about £60 for c.u., £50 each for RCBOs, j/box and tails plus cable (10mm pref.) about £80. Has been a few years since I did my last one, so these costs are VERY approximate. Also depends on how many radial circuits you think you might ever need. I have one per piece of kit plus (currently) a spare.

Do it properly; you won't regret it. Oh, and a dedicated earth rod in the garden, but that can be added at a later stage IF it's viable, depending on your present bonding arrangements.
 
Mike Reed said:
Do it properly; you won't regret it. Oh, and a dedicated earth rod in the garden, but that can be added at a later stage IF it's viable, depending on your present bonding arrangements.
Click to expand...

A rod (or group of rods) in the garden is pretty much guaranteed to be far, far worse than the mains earth. By orders of magnitude (maybe 1000x worse).
 
Michael J said:
A rod (or group of rods) in the garden is pretty much guaranteed to be far, far worse than the mains earth. By orders of magnitude (maybe 1000x worse).
Click to expand...

Oh really? If it lowers impedance (and it usually does), how come it's worse?

This is the first time that I've come across anybody refuting the validity of a dedicated earth; the mind boggles !

Certainly not my experience, nor anybody who I know, or have read of, who has availed themselves of this upgrade.
 
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