Ground in the U.K. versus North America
Posted by: Mike Hanson on 16 May 2001
In North America, the house ground is used only when there is a fault, and the current flows to ground as a safety measure. There is never any current flowing to ground in a "normal" scenario. Therefore, installing a dedicated ground for your stereo is utterly useless.
The only time that the ground is used for current in North America is when you're on a farm. We run only a single wire into most farms. The wire goes to the transformer pole in the yard, where it's connected to ground for the return circuit. I spent a summer testing 1300+ grounds of this type. On the other side of the transformer, the feed to the house is exactly the same as it would be in any city. There is a ground at the house for safety purposes, just like in the city.
The only difference between farm and city is that the potential between the house ground and pole ground on the farm is likely to be closer to equal than in the city, where your house ground and substation ground are potentially far apart. This is a moot point, though, when it comes to stereo use.
Is the electricity system different in the U.K.? Is the house ground actually used as part of the circuit, or is it the same as in North America (i.e. used only to handle faults). If it's the same, then all of this talk of dedicated grounds is pure silliness.
-=> Mike Hanson <=-
quote:
There is never any current flowing to ground in a "normal" scenario. Therefore, installing a dedicated ground for your stereo is utterly useless.
Try this experiment. Get a sensitive volt meter. Find an outlet. Stick one probe into the ground and the other into neutral. You'll find a few mV of juice flowing.
Now do the same with an outlet with a dedicated ground.
Joe
quote:
Stick one probe into the ground and the other into neutral. You'll find a few mV of juice flowing.
Yes, I realize that. It's due to the potential difference between your ground outside and the ground at the substation (or transformer pole, if you're on a farm). Not all earth is at the same potential. Even if you have an excellent dedicated ground, there will still be a potential difference between "ground" and "neutral", because of the distance between your house's and the neutral's ground.
However, the house ground is never used as part of your normal audio circuit. It's there specifically to shunt the current to ground in the case of a system fault. It's important to have a good ground, so that during a fault the nasty electricity can get to the earth easier via the ground rod than through your body.
-=> Mike Hanson <=-
[This message was edited by Mike Hanson on WEDNESDAY 16 May 2001 at 15:03.]
The bonding to gas and water service pipes is equipotential bonding. It is a safety measure and has nothing to do with functional earthing. I'll come back to it in a minute.
Yes Mike, the earth in the UK is purely for safety reasons, but I think you are mistaken if you believe no current flows in it under normal conditions. Everytime there's mains filtering applied (and it's pretty mandatory now for a lot of things to pass EMC regs) - capacitors between L-N, L-E and N-E wires ensure that there is a small bleed of current into the earth wire. The value of such capacitors is limited for safety reasons, because every time a current flows through an impedance you get (drum roll please) a spurious voltage. And there's no such thing as a perfect earth....
Mains filters are limited to leaking 2.5mA IIRC; medical usage limits this to < 1microamp, the whole reason being that all these things add up and as Joe mentioned you get a potential difference appearing between the N and E wires. It is 50/60Hz AC of course, so there's one source of hum for badly designed equipment which doesn't tie all signal references to the same earth point (star earthing :-). So yes, dedicated earth paths can make a huge difference.
The equipotential bonding bit: when there *is* a fault, and a short term current flows of , who knows, 100A+, any impedance in the earth wire is significant, because the earth point at the fault (and with it, the neural phase possibly) could be floating at dangerous voltages above other items which are connected to ground independantly - the taps, the gas fire etc. Equipotential bonding is what stops you being inadvertantly fried because you are standing in the bath (0v relative to ground) while the shower heater is failing (and with it, temporary lifting its ground reference to +50VAC) with you bridging the two together.
Dealing with earthing properly does make a big difference. The equipotential thing, though, is why you *must* check local codes on how to connect an independant earth....
Take care people,
Martin
[This message was edited by Martin Clark on WEDNESDAY 16 May 2001 at 16:18.]
"A popular misconception is that the earthing system is only required during fault conditions. In fact, it also serves a number of vital roles during routine operations. For example, many power systems now include a connection to earth, through which residual and harmonic currents are dispersed to ground. Currents which flow to ground, return to source, forming a loop. These loops will create potential differences which, although small, cause 'noise', 'hum' and possible damage to electronic equipment. This process, together with the increased amount of harmonic current being injected into the public supply network, is a growing cause of significant power quality problems."
this site has very good content that is definitelt relevant to this discussion.
enjoy
ken
One that comes to mind (before I get completely out of my depth) - there's no such thing as a perfect transformer; all have a tiny capcitance between primary and secondary windings, hence a path in for electrical noise (noise voltages wrt earth). Since no two transformers are created equal, noise currents will circulate between the boxes via the interconnects *even though all are tied to one earth potential*.
If they are not tied to a single reference, as NAIM is via the DIN plug, then the problem is even worse, because the PD between references is additive...
I need EE armbands beyond this point though 
Martin
Yours in confusion
Mick....having dedicated spur installed this friday.
On one disc I thought it was better without the earth, giving a richer sound, but with a little less impact. I now realise that the earth adds a considerable increase in dynamic range and tightness of the bass.
The reduced dynamics without the earth simply compress the sound, which makes life easier for my poor Kans (in a 21' room).
Naim systems are very susceptible to RF. The grounding is used to sink the RF energy rather than allow it to corrupt the out-of-band operation of the system. For this to work well the impedance to earth must be as low as possible, across as wide a frequency range as possible.
As well as a possibly better earth connection from the local earth, the very long cables back to the sub-station (100s of metres, with many joins) give a much higher impedance at higher frequencies, reducing it's effectiveness still further just where it's needed most.
quote:
Thanks for the info Martin, but is it not true (please correct me if I'm wrong) that Naim kit uses the earth as a voltage reference?
Yes, this is quite correct.
Naim CD players connect the negative signal pin of their output DIN socket directly to mains earth.
The pre-amps use the earth from the source to provide an earth reference which is continued throughout the amp system via the negative or '0V' connection.
One of Naim's stated benefits for the NAP500 is it's 'bridged' mode of operation, which reduces contamination of the earth reference by return currents from the power amps.
Bridging consists of two amp sections working in opposition to each other (one swings positive voltages whilst the other swings an equal-and-opposite negative one, and vice-versa). The return currents cancel each other out.
cheers, Martin (another one)
-=> Mike Hanson <=-
The mains earth is connected to the casing of most Naim products, and also an electrostatic shield within the toroidal transformer (where fitted).
The quality of the earth (i.e it's impedance) will have a significant impact on how well any electromagnetic interference appearing at the case is conducted to ground, preventing interference to the sensitive analogue circuitry.
Installing a good quality earth, that maintains a low impedance across a wide frequency range will make the system sound better for this reason.
It is also used as a system reference, by bonding signal earth to mains earth at one point in the system (either the CD player, if Naim, or the Turntable).
I'm not sure what the impact on sound would be if you don't have either of these sources though!
Andy.
Andrew L. Weekes
alweekes@audiophile.com
quote:
So we can all agree that having a good low impedence earth for our hi-fi's is a good thing. So does anyone know how to safly install a seperate earth in the UK??
seems so, from the little i have read here and in other places.
enjoy
ken
In UK the green/yellow is for fault protection and screening/exposed metal protection only. The main point here is that although both yellow/green and blue wire are connected via spikes, water/gas pipe bonding etc to the earth, there is a difference between the "green/yellow" earth and the "blue" earth. I don't think this is magic, from what I remember of a substation tour long ago the substation earth (blue wire to you and me) was actually connected to the earth through a low value resistor (actually I think it was a large round tank of water - possibly it was also rusty?) to limit fault currents from damaging transformers etc, presumably because they are large, single winding (ie not centre tapped) types?
In the US there appears to be none of this - the 220V supply is delivered through a two phase (red and black) transformer arrangement. The centre tap of the local transformer (usually serves about 10 homes) is connected to ground via a spike close to the consumer unit. The "neutral" white wires and bare or green "earth" wires are all connected together at this point. The earth wire (bare) appears to to very little. In may houses it does not exist at all!
I suspect there are some interesting improvements for audio possible in the US, I am concerned that the live wire for the 110V is always red rather than the black one, it must be possible to try to balance the black phase load with the red, or use red for one piece of equipment and black for another. I know that in the UK it is a common trick in theatres and halls to run lights from one phase and lights from the other two to reduce the interference between light and sound equipment.
I think the main benefit of a local ground spike in US is to reduce noise at the white wire/bare wire connection point in case the impedance rises during dry weather or the combined house load causes a few volts to appear on the white wires. Also, any signal ground or large chunk of metal (eg pickup arm) that happened to be connected to the bare wire would have a lower impedance to ground through the local dedicated earth rather than the consumer unit earth.
I'd be interested to hear from a US EE and also have someone confirm the above assumptions about the UK.
Jerem
Usually the measurement is around 1-4 ohms. If it's more than 10 ohms, it's considered to be too high. That's the official way that it's done in Saskatchewan, Canada by the utility company. This is what I did more than 1300 times back in 1984.
The interesting thing here is that the "reference" is provided by two stakes, each pounded only one foot into the ground. I've been told by some that you don't even have to pound the stakes into the ground, as simply lying them on the ground is sufficient. I experimented with this claim a little, and it seemed somewhat vindicated. That's why this whole concept of extreme grounds (i.e. multiple rods, star arrangements, etc.) just for your stereo seems a little overblown. Having a dedicated ground does sound useful, though, as it isolates your stereo from the ground activity in the rest of your electrical system.
-=> Mike Hanson <=-
quote:
Having a dedicated ground does sound useful, though, as it isolates your stereo from the ground activity in the rest of your electrical system.
unless i misread your initial posting, you were not very convinced about the merits of this special earthing lark for one's hifi. you appear to have changed your mind now. what convinced you in the end? did you actually try it yourself? just curious...
enjoy...
ken
quote:
you appear to have changed your mind now. what convinced you in the end?
When I first posted the message, I was under the impression that the ground was used only in fault situations, and not during normal operations. Several individuals have indicated that there is actually current passing through to ground on a regular basis, and all the bits of equipment in your house can affect the ground's potential (a.k.a. noise). Therefore, a separate ground for isolation purposes makes sense.
However, I don't think having an extremely low impedance ground, is all that important. As long as it's in the 2-5 ohm range (which most are, unless you live in very dry and/or sandy soil), then you should be ok.
I doubt, however, that I'll ever bother to install one, as I don't really have a convenient place in my yard. I could run a line back into the ravine, but then I have to dig a trench, deal with the extra resistance due to the length, etc.
Omer Shibolet said:
quote:
that job you had, do you do home visits ?
I worked for the power company. They were required to check the integrity of the ground rods in every farm, once every ten years.
BTW, a friend of mine attempted to post this message earlier, and had some trouble with the forum. I'm posting it here for him.
Just thought I could add a couple of thoughts about power delivery here.
Usually, either 4.160 or 13.8kV are delivered to your neighborhood transformer on the pole outside your house. The power is passed through the transformer winding before going to ground. This the actual power is root3 times the input voltage or 2400 and 7967 volts, respectively. The secondary windings provide the 120V in two phases with a neutral also tied to ground (but separately) at the pole. Your house receives the two phases at 120V plus the neutral. As you found previously, Mike, the difference between the neutral and ground can only be 10 ohms or less. Any more and the installer needs to place a ground rod of between 10 and 30 feet long to achieve the low resistance (depending on the soil type). The panel ground on a basement pipe usually does tie directly to the neutral except when there is a higher resistance.
About balancing the two phases. I did that when I installed my dedicated circuit. Appliances like stoves, a/c units and driers tap both phases. The fact is that your neighborhood usage is likely more of a factor. Something most of us have found with the sound improving later in the evening after TVs and stoves are turned off.
As promulgated by Naim, I think a dedicated circuit (unbroken to the panel) is the optimum solution (besides cutting off your neighbors connections ). I actually used 10/3 wire for the circuit and used both the bare wire and a separate wire for ground. If you test the ground-neutral difference in your house and come out to 10 ohms or less, then a dedicated spike is not worthwhile. Furthermore, if you set up a small potential difference between the two grounds, you will get a current and noise. Electricians understand the concept of isolated ground: perhaps something we need for the Naim gear.
In my building at work we used a 20'X20' copper mesh grid to make sure our power feed had a sufficiently adequate ground to prevent any ground loop from forming with its inherent noise problems.
MrI
enjoy...
ken
quote:
Does anyone know whether Naim gear passes current to ground during normal operation? Because they use ground as a signal reference, I would think they might be different from the rest.
and
quote:
When I first posted the message, I was under the impression that the ground was used only in fault situations, and not during normal operations. Several individuals have indicated that there is actually current passing through to ground on a regular basis, and all the bits of equipment in your house can affect the ground's potential (a.k.a. noise). Therefore, a separate ground for isolation purposes makes sense.
I've now found the exact quote on the Naim website re the NAP500, which I think provides a definitive answer to this question:-
quote:
From an early stage of conception it was decided to use bridged amplifiers for each channel of the NAP 500. This allowed the design to have maximised open and closed loop speed, less intrusive protection circuitry and reduced interaction between input and output signals as the very high drive currents to the loudspeaker do not flow through the system earth.
Obviously the other amps do suffer from this...
cheers, Martin
I should test the difference between my wall outlet that services my Naim kit against my main grounding rod. If the difference is greater than 10 ohms I should then install a separate grounding rod for the outlet for my Naim kit. This rod should be installed as close to the Naim kit as is practical.
This right?
Arthur By
quote:
Let me see if I have this straight. Like most houses in the US I have a grounding rod that has been driven into the earth(4 or 8 ft) just beneath my main circuit breaker panel. This grounding rod is connected to the ground connection in my circuit breaker panel which is also connected to the ground wire coming in from the transformer on the electric pole down my street.
I should test the difference between my wall outlet that services my Naim kit against my main grounding rod. If the difference is greater than 10 ohms I should then install a separate grounding rod for the outlet for my Naim kit. This rod should be installed as close to the Naim kit as is practical.
It's more complicated than that. First of all, if your house ground (the rod at the house) is connected to your system neutral (the ground at the pole), then I would question whether this is correct at all. There could be a potential difference between those two locations, and there could be a constant or at least intermittent flow of current between those two locations.
The ground on the outlet should be at the same potential as your house ground (unless you have a break in the ground cable in your walls, in which case it would be infinite resistance).
Ultimately, the dedicated ground is good from a isolation perspective, and if you can add the separate ground, then go ahead with it. This new ground must have a small (let's say less than 5 ohm) resistance, when measured against a "reference" ground. You could use the method that I used when working with the power company, or you could just measure it against your house ground. If possible, you might try watering your house ground before you take this measurement, just to make sure that it's well connected itself.
Before you do anything else, though, I would check with an electrician to see if the neutral is really connected to the house ground. This doesn't sound right at all.
-=> Mike Hanson <=-
My CD player (clearly not a Naim, when you read the following) uses a Telefunken type, so called figure of 8 plug for its power lead. Clearly, it doesn't have a separate earth connection to the mains earth. But, what's a little odd, is that the PCB's have an earthing connection to the chassis.
So, I've been wondering if it would possible/useful/desirable to add an earth connection from the chassis to the mains earth.
The main problem I could think of was if the player feeds the earth "signal" down the neutral connector, and adding a dedicated earth to the player might create an earth loop.
Any thoughts on this? (other than buy a Naim.....)
Chris L
The typical arrangement I have seen with US electrical systems is that you have 3 wires that come in from the pole. two of the lines are insulated an offer 110-115 volts each(but out of phase). The third line is typically uninsultated and goes directly to a buss on the side of the circuit breaker panel where all of the neutrals and ground wires are connected from various outlets in the house. That same buss will have a wire coming out of it that connects to the grounding rod which is typically spiked into the ground 4 or 8 feet. This buss is usually connected directly to the circuit breaker case as well.
The bleed through to ground from Naim kit is confusing to me as the neutral and ground are essentially the same thing by the time the circuit reaches the main circuit breaker panel where they all share a common connection. Most neutrals I've seen are essentially the same size as the ground wire except that they are insulated and are sometimes switched when they should not be.
Anyhow, I'm going to give this a try as it's not that hard to do.
Should the separate spur to the Naim kit have a ground that goes ONLY to the new dedicated ground or should it also connect to the house ground as well?
Another item that is confusing is why is it unacceptable in some municipal codes to have a dedicated earth for an individual circuit? Is there a safety issue here that is being glossed over? I noticed that my washing machine, which has a grounded outlet also provides in its instructions to connect a grounding wire from the chassis to the copper feed pipes. Seems like overkill.
Arthur Bye
-=> Mike Hanson <=-
Mike is right with his original intuition.
In the UK the earth is the same as in the US - just there for safety reasons. NO CURRENT FLOWS through it normally. Electricity needs a circuit! Naim amps, 500 or otherwise do not use mains earth as part of their circuit. Naim's literature is refering to the internal signal ground in their 500. When people talk about star earthing they are normally talking about star grounding of the internal signal returns. Aside from safety considerations your hifi does not need a main earth connection at all. If it does your hifi is faulty or maybe it powers itself from lightning strikes!
Ergo, the dc resistance of your mains earth is irrelevent to your hifi. Wiring your mains earth lines into some mimmick star point is irrelevent. If RF is truely a problem then unless your listening room is on your ground floor and you drive a spike straight down through your Mana stand into Mother Earth it probably won't be very effective. RF impedance is nothing to do with dc resistance. And shielding from RF noise is a whole different subject.
Save your money and time and effort.
Let's keep our feet on solid ground chaps! 
BAM
quote:
RF impedance is nothing to do with dc resistance.
i disagree. RF impedance = dc resistance + capacitive impedance + inductive impedance.
now it could be that at RF frequencies, the dc resistance is totally dominated by the reactive components, i dont know. it sounds like you know -- please educate us.
quote:
Naim's literature is refering to the internal signal ground in their 500.
is there not an electric path between this internal signal ground and mains earth? i had understood there was???
quote:
Aside from safety considerations your hifi does not need a main earth connection at all.
the mains plug on my 250 for example has an earth connection, as is required by safety regulations, as mentioned in the naim manuals. on the 250, where is this earth connected to?? the 250 outer casing?? where?? if outer casing, then lightning can still get at it.
so you disagree with cda.org that some currents do flow in the earth paths?? you have no time for all this noise induced currents business, no??
do you some authoritative references? i have latched onto cda.org as this is the very first document that seemed to go into some detail. have you looked at cda.org??
i do agree that all this concern with earth etc can interfere with enjoying your hifi, and then you get fools like me connecting their 52 binding post to earth (although so far, i am not sure i fully understand why not, if this point is connected to mains earth by some other path anyway...). one of these days, i will learn...
enjoy
ken
quote:
In the UK the earth is the same as in the US - just there for safety reasons. NO CURRENT FLOWS through it normally. Electricity needs a circuit! Naim amps, 500 or otherwise do not use mains earth as part of their circuit. Naim's literature is refering to the internal signal ground in their 500. When people talk about star earthing they are normally talking about star grounding of the internal signal returns.
but in an all-naim system the "internal signal ground" is common throughout all the connected components, and is connected directly to the mains earth in one of the source components.
quote:
Aside from safety considerations your hifi does not need a main earth connection at all. If it does your hifi is faulty or maybe it powers itself from lightning strikes!
I don't know of any way to demonstrate this safely without removing the mains earth connection (which you must not do for safety reasons) but your Naim amps will sound a lot worse with the earth disconnected.
quote:
the mains plug on my 250 for example has an earth connection, as is required by safety regulations, as mentioned in the naim manuals. on the 250, where is this earth connected to?? the 250 outer casing?? where?? if outer casing, then lightning can still get at it.
Ken,
Since the 250 is powered from the mains there is some chance that under fault conditions a live wire will touch the case.
For safety reasons the case is also connected to ground which ensure that this is not a lethal situation.
The mains earth in your 250 is not conncted into the signal path.
cheers, Martin
(Why is it always your posts I find myself fundamentally disagreeing with - it isn't personal I promise)
quote:
NO CURRENT FLOWS through it normally. Electricity needs a circuit!
Quite right it does - radiated fields (RF) to ground via earth - isn't that a circuit, or did I just fail basic electrickery?
quote:
Naim amps, 500 or otherwise do not use mains earth as part of their circuit. Naim's literature is refering to the internal signal ground in their 500. When people talk about star earthing they are normally talking about star grounding of the internal signal returns.
That bit's OK - apart from the bit about not using mains earth as part of the circuit, it IS part of the shielding / screening / safety circuit, a fairly important bit.
quote:
Aside from safety considerations your hifi does not need a main earth connection at all. If it does your hifi is faulty or maybe it powers itself from lightning strikes!
So where does the RF and other EMC go to?
quote:
Ergo, the dc resistance of your mains earth is irrelevent to your hifi. Wiring your mains earth lines into some mimmick star point is irrelevent. If RF is truely a problem then unless your listening room is on your ground floor and you drive a spike straight down through your Mana stand into Mother Earth it probably won't be very effective. RF impedance is nothing to do with dc resistance. And shielding from RF noise is a whole different subject.
Again I'd disagree, although I would say that I believe it's impedance over a wide bandwidth to be the most important factor.
You are right though, in that it is possible for a wire's RF impedance to be lower than it's DC impedance, but it's a tenous argument in the real world. In almost all cases a good low impedance at DC is an essential starting point. Keeping it low as frequency rises is the bloody difficult bit.
The star earthing of mains wiring has EXACTLY the same argument for that of the internal PSU signal return - that of removing shared current paths, allowing one piece of equipment to 'see' the current flow induced in another.
If you have any doubt that there is significant RF current flow in the mains earth, try prodding around with a spectrum analyser - you'd be amazed at how those long wires act as fantastic antennae!
Andy.
Andrew L. Weekes
alweekes@audiophile.com