Noise and DC on mains and new radial

KRM posted:

The spike was fitted by an electrician.

The advice to fit a spike came from Naim (via the dealer), not from Russ Andrews, although I did ask him if it would be ok and he said it would be "fine" as long as it was fitted by a qualified electrician.

The advice from Naim was:

"Use a dedicated earth for the sockets. Use the house earth to protect the cable run, but don’t connect it at the sockets. Get the sockets’ earth from a totally separate rod outside the house. The rod should be as close as possible to the sockets, but needs to be somewhere where the ground doesn’t dry out too much."

Keith

 

Then Keith you should have a certificate with your house documentation to say your utility supply is now (or was) configured as TT. Please check you have that or obtain from your electrician... if something goes wrong your insurance company might need to see that. A properly situated and installed electrode will be provided so environmental variations have minimal impact (suitable depth in shaded location with good local ground conductivity) , and certainly not require user intervention to keep moist (would need to be salty water BTW).

Also note a single electrode DOES NOT remove most RF from the mains, it now allows you to add an additional RF sink set of electrodes safely. If in doubt discuss with a CEPT class 1 licence holder (happy to do this off forum).... electricians don't need to study this or be examined on this in the UK. Earth electrodes utility specifications  in the U.K. are for safety and NOT RF... that is covered separately.

eagle3333 posted:

So Mike, should my sparks be earthing my radial back to dedicated CSU only with no mods to earthing at all?

If your supply is PME (TN-C-S)  Yes (no mods required) .   If your supply has another earthing method,  (there are five categories although only three are in common use)  Your electrician is best placed to advise.

Hi Simon,

I just spoke to the electrician. He will provide me with an installation certificate ( to certify that it has been installed by a qualified electrician). He confirmed that the circuit is connected to the utility earth. Only the socket (so the hifi) is connected to the spike. It isn't duel earthed, therefore. He says it's legal and safe.

You may be right that the spike is pointless from the SQ angle, but Naim recommend so...

Keith

Keith, good stuff, so just to be clear so your certificate converted your house to TT?

if not and you have multiple earth zones which can be used for example where there are outbuildings, static caravans etc, he / you should ensure that there is sufficient physical separation between zones if of a different type such as PME and TT so no person, domestic extension lead or appliance can straddle the zones. So an example you couldn't touch a light switch or metal radiator and the Naim at the same time if earthed by different zones, or you couldn't power a vacuum cleaner from one zone and touch the Naim in another. The risk is from the massive earth current flowing between those zones in certain fault situations that may not be immediately otherwise readily apparent.

But yes local earth could improve SQ if you have noisy earth coming from outside (PME) or from other appliances in your house (zoned) such as a noisy fridge compressor switch.

The certificate will simply say that it has been correctly installed by a qualified electrician.

The domestic ring and the hifi ring are connected to the earth from the electrical supply. The socket is connected to the earth spike, as per Naim's recommendation.

I think you're suggesting that the earth from the supplier or the rod could fail and that would be a problem if you touched the hifi and a light switch at the same time?

Keith

KRM posted:

The spike was fitted by an electrician.

The advice to fit a spike came from Naim (via the dealer), not from Russ Andrews, although I did ask him if it would be ok and he said it would be "fine" as long as it was fitted by a qualified electrician.

The advice from Naim was:

"Use a dedicated earth for the sockets. Use the house earth to protect the cable run, but don’t connect it at the sockets. Get the sockets’ earth from a totally separate rod outside the house. The rod should be as close as possible to the sockets, but needs to be somewhere where the ground doesn’t dry out too much."

Keith

 

If you are doing this then you MUST have an RCD in ALL circuits; without this the arrangement just isn't safe.

 

 

(As a very minor point, how are you running the extra earth wires as this will affect the audio & RFI performance?  Also note that they must be green/yellow insulated.)

KRM posted:
ChrisSU posted:
KRM posted:

I also used a consumer unit which has a 100a isolator switch instead of an RCD (supplied by Russ a Andrews). This is fine as long as the socket is labelled for hi-fi use only. Finally, I have an earth spike.

I'm surprised to see RA selling this consumer unit, which is made of plastic, and will not conform to current UK electrical regs in the majority of installations. That doesn't make it illegal to sell it, but getting it signed off under the current IET regs is another matter.

Hi Chris,

No need to be surprised. The "the plastic, self-extinguishing enclosure conforms to UL94".

Keith

UL94 is a series of flammability tests for plastic materials. The fact that the body of the unit has been made from a material that has passed one of these tests does not mean that the installation conforms to the electrical regs.

KRM posted:

The certificate will simply say that it has been correctly installed by a qualified electrician.

The domestic ring and the hifi ring are connected to the earth from the electrical supply. The socket is connected to the earth spike, as per Naim's recommendation.

I think you're suggesting that the earth from the supplier or the rod could fail and that would be a problem if you touched the hifi and a light switch at the same time?

Keith

Keith, no the risk comes from a fault in the distribution such as a neutral fault at the substation or neutral line fault on a return, in such circumstances the return path may then become any low impedance earth path, the current will seek out the lowest impedance to ground.Now this may be all the relatively high impedance water pipe bonding points in the distribution, the voltage will drop and then the substation hopefully  would then trip off... however if there was a link between the supply earth and your local earth electrode, your entire substation return current could be through that until the substation trips. If there was a wire between the two earths that would almost certainly melt like a fuse wire possibly causing a fire, and more importantly if there was a person bridging the two earths they would be burnt/electrocution if for example brushing against the Naim whilst operating a light switch or another appliance during this fault condition. So yes there are a chain of events that need to happen, but that is what safety is all about i.e. Managing for those cases ... we all know too well when recently what happens when these risks are possibly ignored....

In a TT setup the earth at the supply (if there is one)  and distribution is decoupled therefore in such a neutral fault situation there would be no return path from your local area distribution  via your earth electrode.

Huge posted:
KRM posted:

The spike was fitted by an electrician.

The advice to fit a spike came from Naim (via the dealer), not from Russ Andrews, although I did ask him if it would be ok and he said it would be "fine" as long as it was fitted by a qualified electrician.

The advice from Naim was:

"Use a dedicated earth for the sockets. Use the house earth to protect the cable run, but don’t connect it at the sockets. Get the sockets’ earth from a totally separate rod outside the house. The rod should be as close as possible to the sockets, but needs to be somewhere where the ground doesn’t dry out too much."

Keith

 

If you are doing this then you MUST have an RCD in ALL circuits; without this the arrangement just isn't safe.

 

 

(As a very minor point, how are you running the extra earth wires as this will affect the audio & RFI performance?  Also note that they must be green/yellow insulated.)

That's why I called Russ Andrews and they said it was "fine".

The Consumer Unit is sold with a socket labelled for "not protected by RCD - for hifi use only". 

Keith

Simon-in-Suffolk posted:
KRM posted:

The certificate will simply say that it has been correctly installed by a qualified electrician.

The domestic ring and the hifi ring are connected to the earth from the electrical supply. The socket is connected to the earth spike, as per Naim's recommendation.

I think you're suggesting that the earth from the supplier or the rod could fail and that would be a problem if you touched the hifi and a light switch at the same time?

Keith

Keith, no the risk comes from a fault in the distribution such as a neutral fault at the substation or neutral line fault on a return, in such circumstances the return path may then become any low impedance earth path, the current will seek out the lowest impedance to ground.Now this may be all the relatively high impedance water pipe bonding points in the distribution, the voltage will drop and then the substation hopefully  would then trip off... however if there was a link between the supply earth and your local earth electrode, your entire substation return current could be through that until the substation trips. If there was a wire between the two earths that would almost certainly melt like a fuse wire possibly causing a fire, and more importantly if there was a person bridging the two earths they would be burnt/electrocution if for example brushing against the Naim whilst operating a light switch or another appliance during this fault condition. So yes there are a chain of events that need to happen, but that is what safety is all about i.e. Managing for those cases ... we all know too well when recently what happens when these risks are possibly ignored....

In a TT setup the earth at the supply (if there is one)  and distribution is decoupled therefore in such a neutral fault situation there would be no return path from your local area distribution  via your earth electrode.

Hi Simon,

Thanks for the clarification. I'm looking into it and will bin the spike if there's any issue with safety or insurance.

Keith

Keith, really sensible approach. However it may be entirely appropriate for your house to be put to a proper TT utility supply configuration. It's almost certainly not a big job for your electrician, although you will have a new earth cable running from your distribution board to your new primary electrode that your electrician will additionally validate  the impedance of. You will almost certainly get SQ benefits if you are getting them at present... and you know you will then have a suitable  and most importantly safe setup that gets you closer to your music 

KRM posted:
Huge posted:
KRM posted:

The spike was fitted by an electrician.

The advice to fit a spike came from Naim (via the dealer), not from Russ Andrews, although I did ask him if it would be ok and he said it would be "fine" as long as it was fitted by a qualified electrician.

The advice from Naim was:

"Use a dedicated earth for the sockets. Use the house earth to protect the cable run, but don’t connect it at the sockets. Get the sockets’ earth from a totally separate rod outside the house. The rod should be as close as possible to the sockets, but needs to be somewhere where the ground doesn’t dry out too much."

Keith

 

If you are doing this then you MUST have an RCD in ALL circuits; without this the arrangement just isn't safe.

 

 

(As a very minor point, how are you running the extra earth wires as this will affect the audio & RFI performance?  Also note that they must be green/yellow insulated.)

That's why I called Russ Andrews and they said it was "fine".

The Consumer Unit is sold with a socket labelled for "not protected by RCD - for hifi use only". 

Keith

Keith, did you tell them you were changing over to a TT earthing arrangement?

The necessity for an RCD is shown below (I've assumed a normal 32A MCB is in place, if a higher current limit - 100A switch? is involved the situation is worse)


If an equipment fault connects the 230V line to the equipment case...

With an RCD:  Then at 30mA residual current (e.g. by earth leakage) the RCD will trip.  The RCD will still trip even if the earth spike has 7,600Ω impedance.

With no RCD:  You are relying on the current through the MCB to trip it and disconnect the mains voltage from the case.  This will require more than 32A to flow through MCB and out through the earth spike.  So the MCB will trip only if the earth spike has an impedance of less than 7Ω.


If the ground around the earth spike were to dry out, the impedance could rise above 7Ω.

Hi Huge,

Yes I did. I asked the dealer who asked Naim who emailed a section of a white paper. I then employed an electrician and consulted with Russ Andrews to make sure the consumer unit would be compatible with a spike.

Belt and braces, you would have thought!

Keith

J.N. posted:

Any thoughts on SmartMeters transmitting digital gunk?

John.

No should be fine.. many smart meters  and home automation now use Zigbee which is an IEEE 802.15.4 specification for low power personal networks. Zigbee operates in Europe on the 2.4 GHz ISM (wifi band) and the 868MHz ISM bands and is extremely low power. Naim are also using Zigbee as the remote control frequency on the new Uniti models. There is also an equivalent low power wide area network in development for urban and semi- urban areas called LoRa... which may be used shortly by utility telemetry (remote metering/smart metering) in the U.K. which won't rely on a separate back haul such as GSM or  broadband.

Huge in the U.K., the maximum ground impedance  for a TT electrode is 200 ohms.. anything higher is deemed unstable. To get comfortably below 200 ohms where the ground has limited conductivity then the electrician should use multiple earth electrodes. 

The consideration difference between TT and PME, is that with TT the max fault disconnection time is 200mS where as with PME I believe it's 400mS, but a RCD is not specifically needed if the earth loop reading is very low (very conductive earth) and in which case you could use a MCB. So it is very much down to installation and environment, but in most regular TT installation an RCD would be used, but doesn't have to be used with a TT system.

200Ω max, let's say 20Ω ground impedance so we're nowhere near considering the worst case.

Short line to earth:  230V @ 20Ω = 11.5A, so the MCB won't trip and the earth line will be live, as will be everything connected to it.

I personally don't consider that safe, even if the regulations allow it!

Ok. So after absorbing all the comments above (thank you, All) I plan to ask my Sparks to take a radial off the tails of my mains into a MK Amendment 3 CSU. Into latter he'll put a MK 32amp Type C MCB. From there he'll go into a balanced power supply and from there to a double, unswitched MK Logic wall socket. (Should he star earth inside the socket?) He'll use 10mm2 Prysmian cable throughout. I'll ask him to earth as he sees fit; but, is there a choice to run the earth to either the dedicated CSU, the main household CSU or meter board? If there is, which is best?

There should be an earth terminal near your meter, ask your electrician to connect the new consumer unit to that directly, rather than via your main consumer unit, to give greater isolation. (Assuming, that is, that you're not going to persuade him to stick an earth spike in your garden!)

Mains measure 234v so I'll not be getting a BPS with adjustable taps.

Bt, Airlink offer 1) a standard balanced power supply and 2) a conditioning balanced power supply :

'The Conditioning Balanced Power Supply has the addition of a three-stage EMI suppression filter between the line input and the transformer, designed to suppress either common and differential mode noise or interference.'

This refers to mains high frequency noise, I believe.

I remember from past posts a red flag being waved at 'conditioners' with people saying it had resulted in their music becoming less dynamic. Is anyone able to comment on whether this would be a danger in the instance of the CBPS above?

 Thanks.

I'd just like to say, as OP, that I've presented a distillate of all the above to my fully qualified sparks and anyone thinking along the same lines in terms of improvements to mains power should do the same. Unless they're qualified not to, obviously. Anything that gets done will be done by him and will, therefore, be entirely safe and legal. Having stuck a pair of scissors into a socket aged 7 and been blown across the room, I tremble when replacing a lightbulb.  

My mains measured 234V and occasionally fluctuated to 233V. We didn't check DC offset etc. - because I forgot all about it. I was focused on the mains measurement and which BPS I'd therefore need. Actually I didn't know you could even measure it. I just assumed it's there after finding that turning off all the breakers in the CSU, save for the hifi rooms wall sockets, resulted in less harsh leading edges. Also, my 250DR hums and the hum can become distractingly loud from time to time. I'm hoping the stable power delivery of the BPS will sort this. I'll report back as soon as install is complete. In the scheme of things, this entire undertaking is not expensive - a few quid more than a single Powerline. I'm hoping it turns out to be a no-brainer.

Quick question for the RFI officionados - should the cable feeding my dedicated radial socket be situated a min distance from the cable feeding a socket on the house mains? (My 10mm2 is unshielded Prysmian) I was planning on siting the dedicated socket a few inches above the house ring socket which would bring the cables to within a few inches of each other. Will RFI, or anything else, jump from house ring onto dedicated radial if they're too close at any point? Instal is on Monday

Thanks.

Ian

@eagle3333 - RFI is Radio Frequency Interference - what do you think.....?  Greater separation would be good, IMO, but earthing and/or screening are the real 'fix' to RFI. If RFI is really a problem you have...?

All Naim power amps and power supplies hum - some more than others - but the hum isnt through the speakers generally. Most live with it.... YMMV clearly.

You say a PowerLine is not expensive....? Wow.

I'm not attributing RFI to my transformer hum, Huge. (I was going to put in a BPS to handle any DC, which I hoped would handle the hum; but I've actually cancelled that and decided to be patient and go one step at a time. See what the radial does and add a BPS into the radial, later, if necessary.) I'm simply concerned to make the best of the radial job. I don't know if I suffer from RFI but it seems logical to effect the job in such a way that, if it is present, I don't undo all the good of the dedicated socket by siting it in the wrong place.

I take pictures; I don't do radio interference - hence why I'm asking the question! I didn't say a Powerline wasn't expensive - my reference was 'in the scheme of things' - i.e. it was comparative. If you've spent £30k on your entire system over the years, another £500 is less than 2% of that cost. Seems pretty reasonable for a clean power supply (which is far more reaching than a Powerline) and all that it's reputed to bring. 

The transformer hum / RFI comment was in response to Ian's post.

OK I have a little more time now...

In terms of RFI jumping from cable to cable, approximately speaking, the coupling is inversely proportional to the square of the separation but directly proportional to the length*.

So a short length where the cables are in close proximity will have little effect.  If the cables cross at 90°, then there will be very little coupling at all, even if the outer jackets are actually touching.  The biggest thing to avoid would be running both cables within the same metal conduit.  However from the RF perspective if one or other cable is in a separately earthed metal conduit (N.B. the quality of the earth is specifically important here, so it's not a simple as it appears!) then they can be close with no problems.

* This is also dependent on frequency where the length starts to approach 1/10 of the wavelength of EM waves in air at that frequency.

@huge - Good answer there....  

@eagle3333 - Agree with @Huge that the transformer audible hum is not due to RFI. Believe its more due to harmonics (or 'noise') on the incoming mains supply - which the separate spur ought to help with. BUT - it depends whats causing the harmonics......!  If you can identify the source - and fix it, thats best. 

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