Electrician installed a whole installation RCD

On Wed, 11 Nov 2015 18:53:46 +0000, Fredxxx wrote:

+1

I doubt you'll get an answer to that question any time soon.
I suspect westom doesn't know the difference between insulation breakdown leakage and the reactive leakage you see from the 47nF caps typically used in the EMI filtering circuit of ATX PSUs.
If the leakage is due to failing insulation, that *is* a serious issue which does need to be investigated and put right. Reactive leakage due to EMI filtering otoh, is an altogether different kettle of fish notwithstanding that enough PCs hooked up to a circuit where the CPC wire has gone open circuit can present a human safety hazard (but one would hope that someone would start to question the tingling sensation they get every time they make contact with the case of the PC(s) in question).
One thing to consider with a single *un-earthed* PC is that the leakage source is effectively a 120v supply with a leading reactive impedance of 33.863K ohms (voltage divider effect of a pair of 47nF caps in series across a 240v supply with, effectively, a parallel connection to a very low impedance 240v 50Hz ac supply).
Even the combined effect of ten such unearthed PCs is unlikely to pose an electrocution hazard. It's the peripheral connections that are likely to draw attention to a missing CPC on a UK ring main and a call to an electrician to solve the mystery of why so many devices are getting fried whenever they're plugged in or disconnected from the PC (both the peripherals and the interfaces concerned).
Westom may well specialise in the design of equipment that calls for such low leakage requirements (medical or specialist research equipment springs to mind) but if this is the case, then he's specialised his knowledge to just this subset, an extremely narrow field indeed. Consequently, he's no longer qualified to comment on the wider field of leakage currents from general every day kit without the benefit of a refresher course in "Leakage 101".
Such specialisation to that extreme is very worrying. One such example that comes to my mind is the case of all those early PCI based sound cards (and the PCI based on-board sound chips) that started to appear around the turn of the century which all, to a chip, clipped the line (and CD analogue audio) inputs at -2dB FSD due to the sound card and MoBo manufacturers blindly following the reference design offered by the sound chips makers where the -6dB sensitivity option had been hardwired to reduce the noise floor.
Basically, this was achieved by doubling the reference voltage for the ADC but forgetting the need to double the line input buffer amp supply rail voltage to raise the already marginal clipping level that was otherwise sufficient when the more sensitive setting had been chosen.
I think it took a good (well, bad really) 5 or more years before the penny finally dropped and the problem was properly addressed. You had to be overly focussed (specialised) in the digital aspect and totally ignorant of the fundamentals of audio circuitry design to miss that particular "Schoolboy Howler" of design incompetence to make that mistake (and worse still, perpetrate it for so damned long!).
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On Wed, 11 Nov 2015 16:44:02 +0000, westom

Oh dear.

You mean like the EU, the USA, Switzerland, Singapore etc?

Which ones?

Nope.

Try the one quoted - IEC 60950-1 (Information Technology Equipment) (IEC 60950-1, 2nd Ed, 2005-12 to give the current version its full title).
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replying to Peter Parry , westom wrote: For protection of human life, an RCD must trip at 5 milliamps. Higher currents (ie 20 milliamps) are permitted if human protection only requires 'let-go' or ventricular fibrillation protection. One standard (that now applies to North America and will eventually appear in the UK) is UL943.
More facts from design standards. Currents less than 0.5 milliamps are considered safe. Current between 0.5 and 10 milliamps cause involuntary muscle contraction resulting in injuries. Currents between 10 milliamps and 100 milliamps can cause breathing difficulties or even fibrillation. A 100 milliamp RCD is an inferior safety device. Any fault that trips a 100 milliamp RCD is well above human safety requirements.
How does one design equipment to operate without tripping RCDs that do human safety (ie 5 milliamps)? That equipment leaks less than 100 microamps. One ANSI standard permits leakages up to 500 microamps. BS standards will eventually adapt what has long been standard by UL, CSA, IEEE, and others. Many BS upgrades eventually use phrases directly taken from those other, older, and safer standards. Apparently you need not meet international standard.
Properly designed equipment need not leak more than 100 microamps. Designs typically target 60 microamps. JCAHO and NFPA 99 defines less than 50 and 10 microamps. Another standard permits up to 300 microamps from an asssembly of many electronic devices. Another standard for small electric motors with only one layer of insulation permits up to 100 microamp leakage. All well below an obsolete 3.5 milliamp number that would cause problems with current technology 5 milliamp RCDs. Even in the days of vacuum valves (tubes) did not leak that much.
Now back to the OP's problem. If a 100 milliamp RCD trips, then a serious and troubling human safety issue exists. Above numbers say why that is dangerous. Fault can be in appliances or in household wiring. Or even a combination of both.
An informed engineer would not hype on the irrelevant - badly designed hardware that leaks 3.5 milliamps. As if obsolete standard are good enough. Microamp leakages numbers were standard and routinely achieved even 40 years ago. If a fault does not exist, then even 5 milliamps combined from many appliances would not exist.
A design engineer would target the topic rather than promote obsolete safety standards. The OP's tripping RCD indicates a serious human safety issue.
In one case, that fault (that was in building wiring) did not exist until an appliance was powered by that circuit. It was a more interesting problem.
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On 12/11/15 05:44, westom wrote:

Or just a leaky heating element in a cooker.
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Or one of the water heaters he has.
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On 12/11/2015 05:44, westom wrote:

Nonsense.
Firstly you need to understand that shock hazards are related not just to current flow, but also duration.
The shock hazard curves are shown here:
http://wiki.diyfaq.org.uk/index.php/File:RCDShockHazardCurve.png
Secondly keep in mind that RCDs to not limit the current flow in a shock situation anyway.

The UK requirement for direct contact shock protection specifies 30mA devices for general use. 10mA threshold devices are available for specialist applications, but are not in general use.
Generally they will operate within two mains cycles (40ms). Its this quick operating time that is the actual protection mechanism, not the trip current.

No one was suggesting otherwise, so you can stop repeating yourself.
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On Thu, 12 Nov 2015 05:44:01 +0000, westom

Pity that all domestic ones trip at 30mA then.

BS 7671:2008+A3:2015 IET Wiring Regulations Seventeenth Edition came into effect in July 2015. Residual Current Devices must meet the standards in BS EN 61008-1:2012.
You are suggesting that these will in some way be replaced by UL943 (Class A, single- and three-phase, ground-fault circuit-interrupters intended for protection of personnel, for use only in grounded neutral systems in accordance with the National Electrical Code (NEC)), dated 2006?
You do realise a GFCI and an RCD are functionally identical?. However a GFCI incorporates an over current trip so is closer to a Residual Current Breaker with Overload (RCBO) than a RCD. There will normally be 1 GFCI per socket outlet (Often incorporated into the socket itself) or small group of radial wired sockets rather than the RCD covering a ring main which will have many sockets.
Under present UK rules all sockets must have residual current protection, under the somewhat more lax American NEC rules only those for use in wet areas need residual current detection.
What on earth makes you think the older UL943 will replace more modern standards?

Which design standards?

No it isn't, it has a perfectly valid role to play in TT earthed circuits.

That's probably why those installed for protection of the users are rated at 30mA.

If you are referring to the US wiring system of having one GFCI per socket - this will allow for the maximum 3.5mA leakage current from your computer.

Do you actually understand the standard naming conventions and the hierarchy of standards? National standards specify the requirements for application in the particular country. British Standard – BS denotes Britain's National Standards which are controlled by the British Standards Institute (BSI). EN denotes a Standard which is adopted by the European community and is controlled by the European Committee for Standardisation (CEN). European standards are aimed at facilitating commerce between the countries of the European community. Once a European Standard has been agreed it supersedes any existing national standard and becomes the new national standard. In Britain these Standards are then prefixed with BS EN. ISO denotes a worldwide standard issued by the International Organisation for Standardisation. Once an International Standard has been adopted as a European Standard it supersedes the existing European standard. In Britain these Standards are then prefixed with BS EN ISO.

Why on earth would you make all domestic equipment conform to medical equipment standards when there is no advantage in doing so and a considerable cost increase?

You have obviously never worked on an old USA design TV.
However, here is a clue. Old valve equipment didn't use switched mode power supplies and didn't have to meet any RF emission standards. Indeed many TV['s were quite effective jammers of short wave radio bands).

It is a 30mA RCD which is tripping.

The "obsolete" standard is several years younger than the American one you quote.

40 years ago switched mode power supplies (SMPSU) were uncommon and radio frequency interference wasn't an issue. With SMPSU you need noise filtering to meet the EMC requirements and that introduces leakage paths.

. The standard you are referring to was only published 3 years ago.
I am rather concerned that someone claiming to be involved in the design of electronic devices seems to never have heard of the appropriate International standards.
Next thing you will be telling us to switch to 110V because it is "safer".
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replying to Peter Parry , westom wrote:

Again ignorance of what must be done all over the world so that equipment will work in regions with better safety standards. For example, everything on a circuit (ie some 20 devices operate on one 5 milliamps RCD) without tripping it. Because that is found in North American venues and therefore in major facilities throughout the world. No problem since electrical equipment must leak typically less than 100 microamps. Even construction sites must have many equipment on one 5 milliamp GFCI without tripping. Any equipment that leaks 3.5 ma would cause consternation on job sites. Same 'less than 5 millampss' applies to secure facilities all over the world because that equipment is also used in and must also operate on North American's much safer GFCI standards.
Return to the point; to what is relevant. A tripping 100 mA RCD means a serious human safety issue. Move on to what the OP must do to have human safety.
You are arguing nonsense using standards that are considered insufficient in many venues and for human safety. Relevant numbers for human safety were for faults of less than one second. 30 milliamp protection is too high for what are normally one circuit powering 20 appliances. Everything you have posted demonstrates only local knowledge; insufficient for international design requirements. And is irrelevant to the OP's problem.
Apparently you want to argue safety standards that are inferior to what is found elsewhere; rather than address the purpose of this thread. A useful engineer would address reasons for RCD tripping either due to appliance failure, interior wiring faults, or a combination of both. And yes, we have seen where an RCD would only trip due to a combination of both - which can make solutions challenging. Nuisance tripping happens in venues with safe wiring when appliances leak an excessive 3.5 mA. But that is not the OP's problem. OP has a much worse fault that exceeds what is required for human safety. Move on to what is relevant here.
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On Thu, 12 Nov 2015 14:44:01 +0000, westom

You have extension leads with 20 things plugged in to them from one socket!

One thing most of the world didn't follow the USA on was, very wisely, their dire and rather primitive electricity installations.

Which standard mandates that for IT equipment?

That might explain why electrocution is the second leading cause of death on American construction sites. 15% of traumatic deaths in the US construction industry are due to electrocution compared with 1.5% in the UK.

The population of the USA is about 6 times that of the UK. In the year 2009 about 100 Americans died due to electrocution in the home from consumer products alone.
In the UK in the same year the number of people who died from electrocution in the home from all causes was 5.
I hope you don't feel offended if we stay with our "inferior" system.

We all agree that a 100mA RCD does not provide adequate personal protection but we are not talking about that but a 30mA one.

You mean the USA having an electrocution death rate at least 3 times higher than the UK is because of their "superior standards"?
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On 2015-11-12, Peter Parry wrote:

Not directly, of course: you daisy-chain the extension leads. Have you never seen a meeting where 20+ people have laptops plugged in at the same time.
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On Thursday, 12 November 2015 19:30:09 UTC, Adam Funk wrote:

No need to daisy-chain; up to 20 sockets here:
http://www.olson.co.uk/left_right_cables.htm
Owain
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On 2015-11-12, snipped-for-privacy@gowanhill.com wrote:

I haven't seen those before, but I've seen plenty of situations where they would have been useful!
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Olson stuff is awesome. It's often available on ebay, and I have 4 large strips in my study, totalling 76 sockets ...
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On 2015-11-13, Huge wrote:

Your RCDs must be tripping all the time.... ;-)
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On 13/11/2015 14:01, Adam Funk wrote:

Thankfully much equipment is double insulated associated with leakage currents only Mr Westom can dream about.
I doubt the sockets will be fully populated!
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Never. There aren't 76 things plugged in. About 20 or so.
(And I miscounted, there are 5 strips. Same number of sockets, though.)
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replying to Peter Parry , westom wrote:

Again, your knowledge is only of local wiring standards using inferior protection.
20 appliances on many receptacles can and must be powered by one RCD that will trip on 5 milliamps. You should have known that long before denying and posting. Many appliances on one 5 milliamp RCD is routine in venues where human safety is better.
Informed engineers routinely design equipment to leak less than 100 microamps. A 3.5 milliamp leakage is unacceptable in venues where better safety exists. Properly designed equipment must work without tripping any RCD anywhere in the world - even on construction sites. 20 items, each leaking 3.5 milliamps, is unsafe, unacceptable, and routinely avoided by simple and proven designs.
You again subvert this thread with what is totally irrelevant. OP has a fault so serious as to even trip a 100 milliamp RCD. Can you concentrate on the topic rather than posting feeling and myths generated by ignorance? Why do you routinely and repeatedly ignore the OP's problem? Why do you subvert this thread by promoting unacceptable designs and obsolete standards? Can you assist the OP?
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On 12/11/2015 19:44, westom wrote:

You sound unemployable.

Nonsense. No "must" about it.

This thread is subverted by you when the OP was asking about a 100mA RCD. Do keep up rather than showing your ignorance, or even a lack of comprehension skills.
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On 12/11/2015 19:44, westom wrote:

No, we are well aware that wiring in the US is generally crap. Crap electrical accessories, use of Ali cables, wire nuts etc... shudder!

Please try and get a clue. Go look at the specification of a typical RFI suppressor and explain how you are going to design your equipment to have a leakage of less than zero!

Is readin not your strong point? The OP said (and I quote verbatim):
"an electrician installed a whole installation 30mA RCD recently"
That is what is tripping, not a 100mA RCD.

Because we can read.
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On Thu, 12 Nov 2015 19:44:01 +0000, westom

Why?

Better than what? The US standards are dire. Very few are International standards because no one is willing to downgrade to meet them.
If they are so good why do so many more people in the USA (as a proportion of population) die of electrocution than in the UK?
I presume the "venues" you are wittering on about are Wally's burger bar?

Name some (and when you do, remember how many more people are electrocuted at work and at home in the USA than in the UK).

There are no documented cases of anyone being killed or injured by a circuit protected by a 30mA RCD.

No it doesn't, as you have been told several times by others. He hasn't fitted a 100mA RCD.
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