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Topic Title: Requirements for Hi-Fi enthusiast
Topic Summary: No RCDs and separate earth
Created On: 16 April 2013 08:37 PM
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 16 April 2013 08:37 PM
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JZN

Posts: 556
Joined: 16 November 2006

I've done a few of these and they all ask for different things. I have a few questions on the latest.

I've got to install five unswitched double socket outlets to supply the music system. They will be MK as these "sound better".

I have to install a new consumer unit with one MCB supplying the five outlets. Low load so 16Amp mcb. He's requested no RCD but wants cables concealed in plaster. On top of this they are sockets so the regs require RCD. Can i use the "under competant supervision" get-out here as the user knows what they are for and the limitations on what they can be used for?

The supply is PME and he wants a separate earth rod driving in. Again I will be making this section of the installation a TT so 30mA RCD is a must right?

On the earht rod subject - I'd normally run the main earth cable from the rod to the earth terminal bar in the consumer unit. Apparently that's not the way to do it for Hi-Fi. He's requested that the main earth cable connects to one of the sockets. Is this acceptable? While it is a bit unorthadox, I can't think why not.

Any thoughts (appart form the obvious rude ones).

John
 16 April 2013 08:48 PM
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mikejumper

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TT will need to RCD'd.

As for separate earth to sockets, how will you maintain equipotential within the building?
 16 April 2013 08:51 PM
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paulskyrme

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No answers, just a bunch of questions for you to consider...
How can you ensure separation of earthing systems?
Would this be required?
How can you protect the buried cables without an RCD?
Can you ensure that the user is competent under BS7671?
Can you get away with just labelling the sockets for dedicated use?
 16 April 2013 08:54 PM
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dickllewellyn

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Is the earth rod for functional purposes in addition to the instalation earth? I've done this before in R&D labs to cut harmonics. If the rod is to be the sole earth for the sockets, then you will need to install an RCD for TT purposes.

If the sockets can be installed without RcD then labelling should suffice, particularly if they are in a cupboard or similar. Have you offered special Hifi socket outlets? http://www.russandrews.com/pro...-UltraSocket-1901.htm

I would say it takes a very special ear to notice the difference! I love how audiophiles insist on these sooper dooper terminals and cables etc to make the sound more pure, and then use valve amplifiers because they prefer the more mellow sound owing to the fact that every waveform is clipped and altered undoing any good that the magic terminals made!

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Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 16 April 2013 08:59 PM
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JZN

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I did think of the equipotential but the risk would be very low. The only metal parts would be the unit cases and there are no other conductive parts nearby. Not even any more sockets near.

Paul, I cant guarantee separate earths and nor do i care! If they wantt o pay for this stuff and it's not against the regs then it's fine with me!

I did think of labelling the sockets to prevent other use. The user is not competant under BS 7671.

I've been thinking of installing a unit with RCD and telling him where he can get a double pole main switch so that he can change it if he really wants. My EICR will obviously not the RCD and it's trip time.

John
 16 April 2013 09:02 PM
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JZN

Posts: 556
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I think the whole separate earth issue is not functional, it's just to remove noise on it due to other well known leaky items such as computers etc.

John
 16 April 2013 09:37 PM
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jamieblatant

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Having worked for some hardcore audiophiles I can confirm

There nutcases

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 16 April 2013 09:41 PM
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peteTLM

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Originally posted by: JZN


I've been thinking of installing a unit with RCD and telling him where he can get a double pole main switch so that he can change it if he really wants. My EICR will obviously not the RCD and it's trip time.

John


If you are creating a TT system by installing a rod and having this to a separate CU dedicated for these sockets- ITS TT YOU MUST HAVE AN RCD!! Not optional.

Personally, i think id get him to prepay me on the condition that they have this separate system dismantled the day they move out- pre paid so its not 'overlooked'.

TT with no RCD???"£$%^

-------------------------
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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 16 April 2013 10:00 PM
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Zs

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John, nice job. The world needs enthusiasts.

I was married to an audiophile. I'd never have admitted it at the time but yes, some of these things do make a difference. Years later and I have a clean earth for my hi fi and the guitar amp.

I'm very interested in the connection to the first socket instead of to the MET at the DB but I'm wondering if it is going to help? The ( assumed from here) 1.5mm green and yellow with the possible changes in potential as it encounters a 16mm are irking.

BS7671 is not statutory and others will throw them at you so I'll not. But you have a duty of care. Might I suggest that if not you, someone will do this for an audiophile? Perhaps a sound letter of instruction from your client. He's asking for quite a few breaches.

Now, On the subject of the RCD. It doesn't make any difference to my system with a clean earth. My earth rod is practically under the lounge and not all that far from the TNCS incomer. I would be very cautious about going without because I imagine your customer has some very expensive kit which would do well to be protected.

MK are the best? Hmmmm I wonder about that. They only have one earth terminal though....Hmmmm. I'd wager that contactum with their lovely solid round terminals would be a better connection.

A fault at the DB.....down a bit of 1.5mm to the first socket...through all the kit....down a bit of 16mm to an earth rod....That's a lot of very confused charged electrons.

But let me know if it works wonders.

Have you heard the one about the lump of tin foil up your nose and standing on one leg?

Oh, something else...My guitar amp developed an earth buzz recently. It went on for days and was a big deal in Zs towers. Turned out I had the iPod lead plugged into it but without the iPod connected to the other end. That wasn't snake oil earth buzz, that was proper. I can see where they are coming from.

A touch envious of this job. Enjoy.

Zs

Edited: 16 April 2013 at 10:10 PM by Zs
 16 April 2013 10:02 PM
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rocknroll

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This sort of environment requires specialist considerations, like oversized cables, single point and technical earthing etc; so dont expect a good clean mains supply derived from a simple domestic installation, 90% of computer crashes are caused by power problems not software what most people believe, noises are blamed on poor earths when they are often found to be poor mains, power conditioners do not give the cleanliness you require and UP systems are prone to a lot of the mains borne interference than you would imagine.

When faced with these problems it is the cabling especially from the supply that is grossly undersized and you need to double the csa, in the case of sockets use 4mm² instead of 2.5mm² and then sort out the earthing to get as low as an impedance as possible, reorganise the wiring so that the studio power is at low level and all other circuits, lighting, AC etc. at high level. One of the biggest problems is power and guitar amplifiers which draw current in pulses and at the lower end of the sound spectrum which can cause some horrendous voltage depressions therefore introducing harmonics into the equation, so it is essential that large size cables are used, this is important for the earth as well, audio equipment has the bad habit of dumping everything into earth so impedance is the biggest problem, as I said the problems dont often relate to the supply but the installation itself is the culprit.

Although more suited to a small music studio set-up the same rules apply for a dedicated hi-fi set-up if you want quality.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 16 April 2013 at 10:09 PM by rocknroll
 16 April 2013 10:24 PM
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Zs

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I agree with that R&R....it's a 4mm radial with a 4mm cpc here and serves only three double sockets. But I'd draw the line at the suggested earth connection from the OP.

The DB it runs from, like JZN's, is competely separate from the main one and has very little leakage with music on. It's only a garage DB, nothing special. The main household board has about 14mA most of the time.

And get those pesky LED lights in the dustbin.

Zs
 17 April 2013 01:04 AM
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M.Joshi

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Many audiophiles believe that an RCD doesn't provide a 'clean' electrical supply to their equipment and colours the sound. One of the UK retailers (Russ Andrews) previously advising against using RCDs now do recommend their use following 17th Edition guidelines. They used to sell a specially treated Hager DIN enclosure with treated RCBOs intended for exclusive use to supply audio equipment. I think they treated the Hager parts with DeoxIT spray?

I couldn't find the Hager items on the Russ Andrews website however, you might find this link useful when trying to understand an audiophile's mains requirements:

http://issuu.com/russandrewsac...nsupgradeguidesingles

As 'dickllewellyn' mentioned, you may want to recommend the specially treated unswitched MK sockets while you're there too!

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 17 April 2013 08:09 AM
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dickllewellyn

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When I had to instal harmonic dampening earth rods in the past, we were instructed to use tinned copper braid rather than earth wire. The suspect wavelengths were worked out, and this decided the distance between earth rods wired in series. I wish I understood what I was doing and why!

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Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 17 April 2013 09:40 AM
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AJJewsbury

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Paul, I cant guarantee separate earths and nor do i care! If they wantt o pay for this stuff and it's not against the regs then it's fine with me!

Regs say that all exposed- and extraneous- conductive parts that are simultaneously accessible are to be connected to the same earthing system (411.3.1.1). Does the householder possess any extension leads and class 1 appliances? I'd certainly not be comfortable with a PME install with a TT "hole" in the middle of it - and I suspect the DNO might not be either. Tingles in normal supply conditions would be worrying enough, a broken supply CNE doesn't bear thinking about.

How can you protect the buried cables without an RCD?

That's easy - use steel conduit, or MICC, SWA, BS 8436 cable etc. Doesn't need to be mechanically protected, just as long as it has a concentric c.p.c.

I reckon it's a choice between RCDs and PME. Keep PME and use a low impedance (i.e. "clean earth" as it used to be called) c.p.c back to the MET - add an additional rod if you like; or TT the entire installation.

Only other option I can think of is to buy a whopping great 1:1 transformer and create your own local TN-S system for the entire installation. I doubt he'd want to pay for the standing losses though.

- Andy.
 17 April 2013 09:40 AM
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mikejumper

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Originally posted by: JZN
I've got to install five unswitched double socket outlets to supply the music system. They will be MK as these "sound better".

I wonder sometimes whether 'Hi-Fi enthusiasts' have any idea what happens to the mains supply after it enters one of their bits of kit.
 17 April 2013 09:49 AM
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BigRed

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The words Snake oil and more money than sense spring to mind....
Love how audiophiles worry about noise and then used unbalanced inputs for their "hi fi"
Want no noise and professional sound? use professional equipment.....
 17 April 2013 11:54 PM
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sparkingchip

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I would not be prepared to install to this design, even if the client was signing the design section off of a three part installation certificate.

I have seen some nasty "Hifi electrical installations" which have been potentially lethal, such as 6mm twin and earth connected into the tails at the meter with only the 100 amo REC fuse to protect it buried in the flower bed less than 150mm deep to get to the other side of the house where the is a consumer unit without any blank covers leaving the live busbar exposed to touch, then B32 MCBs supplying sockets via 2.5mm twin and earth without any RCDs.

I'm with Jamieblatant, nutcases.
 17 April 2013 11:58 PM
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sparkingchip

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One way AC cable anyone?

http://www.russandrews.com/art...russdirectionality.htm


http://www.russandrews.com/viewindex.asp?lookup=0®ion=UK¤cy=GBP&article_id=kimbermains_differences&customer_id=PAA1775047913083TSBOFNSSEGVWNZIG


http://www.russandrews.com/pro...913083TSBOFNSSEGVWNZIG
 18 April 2013 07:00 AM
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ebee

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Have you seen his prices?

Nutters, snake oil and he must be minting it in!

I wonder if Audiophiles do the equivalent of a "blind test" on products?

"Deaf Tests" perhaps ?

Call me a Philistine if you like but I look at Hi Fi to this degree like Wine.
A lot of rubbish spouted about the subject

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 18 April 2013 07:36 AM
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JZN

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Ok. Thanks all for the input. I've talked it through with him and will be TT-ing the whole installation so no PME anywhere. I'll be installing a 4mm radial circuit with 4mm CPC. There will be an RCD as noted on my EICR, but he says he'll take it out later and replace with double pole incomer.

Not sure what music he's into but I was tempted to ask if he ever listened to the music or just what it sounded like. The last audio nut i worked for was into Paul McCartney FFS!

Thanks

John
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