Grounding old equipment

[Specmaster]

I had a customer that said every time she closed the refrigerator door it blew her house fuse.  Cause?  Her "electrician" had decided since neutral and ground were the same he would ground the socket by tying them together.  Problem?  He tied ground and hot.  There most not have been a good earth ground in this place because it didn't blow the fuse until she shut the door and it contacted the register duct.  This thing was right next to the sink where she did dishes.  Can you imagine if she decided to reach over and get a cold drink?

Again, you add something that wasn't there and you become a potential target.  Yes the fault would REALLY be with the socket.  You want to go to court and prove that?  You charge enough for that repair to cover the legal costs if they arise?  Some of my old stereo equipment came with a ground screw on the back.  Of course back them most house receptacles were 2 wire.  I lived in one place where they ran wire up through the old gas light pipe.  But I digress.  But then again, so has this thread.   

Was this fridge wired up on a 2 pin plug by any chance? If so then it just highlights the issues I mentioned before and the fitting of a 3 pin plug and the introduction of an earth connection to the external metal work should really be belt and braces and not introduce any additional risk or problems surely?

[floobydust]

Appliances, like refrigerators are PE grounded, 3-pin plug as you call it.
It's cheaper than double-insulation for the compressor motor, defrost heater etc.

[Gyro]

Finally stop quoting your 4mm and 5mm mantra as the only safety metric,

Gyro, you must learn to READ.

I have never claimed 4 and 5mm as the only safety metric. I have always mentioned that the environment must be considered.
Already in my first post I wrote:

"This is a stereo. It's meant for a normal domestic environment, i.e. no excessive humidity or dust. It is not ment to be mechanically abused as power tools are."

I have also written:

"The intended use and environment plays a big role in the design and certification process. Equipment meant to be used in a normal office / living room environment is subject to lighter regulations than something meant for use in the kitchen or outdoors or as toys for instance."


But you prefer to be blind for this. Only you can tell why.





Electrical safety has nothing to do with words written on a paper.
Legal safety has something to do with words on paper.

No product will become safe because of words, and no product will become unsafe because we call the product something else.

What makes a product safe depends on the environment and physics. 4 and 5mm will provide the clearances necessary for normal mains voltages in a normal office or living room environment, regardless of what is written on any paper or what we prefer to call the product.

 The reason the standards increases this distances for certain products is not because we call the product someting else than computer or fax or monitor. The reason they demand more clearance for some products is because they know that those products probably will be exposed to a more demanding environment, for instance people acting stupid. They increase the safety margin. Not necessarily because the product itself needs it, but because of the expected environment. They don't make a separate standard for every product imaginable. They try to group them according to expected use and environment.

Your computer monitor with 4/5mm distances is considered perfectly safe when you use it as a monitor for your computer in your living room. This monitor will not become unsafe just because you hang it on the wall in the same living room and uses it as a TV together with a TV dongle. According to words written on paper, it is now a TV and should be tested as a TV to be conform with a more demanding standard. Because of this it is legally unsafe. It is still electrically safe because it is still used in the environment it was designed for. If you move it to the kitchen or outdoors, you can find it to be both electricall and legally unsafe because the environment is too different from what it was designed for regardless of being used as a TV or a monitor.


But - I don't think you ever will get it.
It seems like it is impossible for you to see the difference between how to find out if an existing product can be considered as safe to use, and the design process needed to create a new product that will have to follow all legal requirement in today's legislation.

Sigh, ok you've provoked me into final comments 

1. I could go on at length about degree of contamination - often old consumer equipment is very dusty inside, in a smoker's home MUCH worse.

2. As Hero999 states, the mains supply is subject to transients. Scores of pages are spent in the Test equipment section on the safety of DMMs which might very occasionally be connected to the mains by unwise people. Most of those have creepage and clearances greater than 4/5mm but they lack the additional surge withstanding components to withstand possible transients. AV equipment is normally permanently plugged into the mains.

I could go on but since you have chosen to differentiate your definition of electrical safety from the Legal definition of safety....  and since this is the BEGINNERS section of the forum...

Which definition of safety will an Insurance Company or Court base it's judgement on in case of death or injury through Electrocution or Fire? The LEGAL definition of safety or the tronde^TM definition of safety?

[Specmaster]

Appliances, like refrigerators are PE grounded, 3-pin plug as you call it.
It's cheaper than double-insulation for the compressor motor, defrost heater etc.

They should be I agree, but the post by hermit sort of suggested that maybe the 3 pin plug had been removed and a 2 pin one fitted in order to fit an existing 2 pin socket otherwise why would the "electrician" feel the need to tie earth and neutral together? As he said there was a very bad earth (ground connection in the house anyway) and it was only when the fridge actually touched a duct. So if it was a 2 pin plug, incorrectly inserted in the socket then it would not blow the fuse until the live metal of the fridge physically came into contact with a good ground such as the duct? 

[hermit]

Was this fridge wired up on a 2 pin plug by any chance? If so then it just highlights the issues I mentioned before and the fitting of a 3 pin plug and the introduction of an earth connection to the external metal work should really be belt and braces and not introduce any additional risk or problems surely?

The fridge was new so it was three pronged.  It was an old house so there were only 2 wires to the receptacle.  That's why the "electrician" got the bright idea to run a wire between the ground and neutral on the new socket.  In theory I guess that is better than leaving the ground disconnected.

Quick edit to clarify something in a post after the one I'm answering.  The house was old so it was a 2 wire system.  I have no idea how the heating register ended up being ground.

Off topic, but hey does that matter at this point, I had one instance where someone ran 240V to their garage and terminated it with a 120V outlet.  Then they sold the house and the new owner had no idea.  I was trying to figure out how they blew every motor in the machine.  As I was getting back into the truck it struck me the light bulb seemed awfully bright.  I got back out and went back to measure the voltage.   Consumers can be so much fun.  In this case it was the repair technician put at risk by the customer.

[Specmaster]

Was this fridge wired up on a 2 pin plug by any chance? If so then it just highlights the issues I mentioned before and the fitting of a 3 pin plug and the introduction of an earth connection to the external metal work should really be belt and braces and not introduce any additional risk or problems surely?

The fridge was new so it was three pronged.  It was an old house so there were only 2 wires to the receptacle.  That's why the "electrician" got the bright idea to run a wire between the ground and neutral on the new socket.  In theory I guess that is better than leaving the ground disconnected.

Oh OK that answers that question nicely then it was one of those "Electricians" who can't tell live from neutral.

[Gyro]

It definedly is not my fault if it is too much to ask to understand the anecdote, which by the way is pretty close to the typical imaginary excercises (like the story hermit shared) used in introduction level electrician training by many teachers.

@Vtile,

I'm sorry. I have realised that I accidentally attributed some of tronde's comments to you in my post earlier today. I have gone back and added a clarification. Please accept my sincere apologies, I should have been more careful - and more gentle towards you as a result. 

Chris

[floobydust]

I have seen electricians connect an outlet's GND to NEUTRAL instead of leaving it floating, with old (1950's and earlier) houses in North America, that have 2-prong outlets.

The reasoning for this - cutting off the (fridge's) 3rd-pin (GND) it's more dangerous leaving it floating.
Since NEUTRAL is bonded to earth-ground in the breaker panel, it ends up being a ground connection.

This isn't my idea, it doesn't meet electrical codes. The alternative is to update the outlet by ripping up walls and stringing a GND wire, do it right.
Too bad that electrician connected to HOT and didn't check.

[Vtile]

It definedly is not my fault if it is too much to ask to understand the anecdote, which by the way is pretty close to the typical imaginary excercises (like the story hermit shared) used in introduction level electrician training by many teachers.

@Vtile,

I'm sorry. I have realised that I accidentally attributed some of tronde's comments to you in my post earlier today. I have gone back and added a clarification. Please accept my sincere apologies, I should have been more careful - and more gentle towards you as a result. 

Chris

Well, like wisely said by Hero (pun intented) the subject usually ends up in some form of depate between - I suppose - people with different backgrounds. 

[Specmaster]

It definedly is not my fault if it is too much to ask to understand the anecdote, which by the way is pretty close to the typical imaginary excercises (like the story hermit shared) used in introduction level electrician training by many teachers.

@Vtile,

I'm sorry. I have realised that I accidentally attributed some of tronde's comments to you in my post earlier today. I have gone back and added a clarification. Please accept my sincere apologies, I should have been more careful - and more gentle towards you as a result. 

Chris

Well, like wisely said by Hero (pun intented) the subject usually ends up in some form of depate between - I suppose - people with different backgrounds. 

I love it when a discussion takes multiple routes like this, its good to promote healthy debate and it can be very educational as well so wheres the harm. We are no different to other so called experts, some of whom cannot even agree on the correct way to make a cup of tea. There is always at least 2 sides to every storey and it is nice to see other peoples view on something and respect their views and experience, no man knows it all.

[HackedFridgeMagnet]

pls Don't be rude to others in the thread, there is no need.

I actually agree that there often is a difference between what is safe and what is legal. But for ease of effort and ease of mind I just normal go as close to the letter and spirit of the laws as possible.

Sometimes it's not easy.

In this case what is the law? And here's a clue, it's not an international standard. Though no doubt it will be close.
I haven't seen anyone quote the relevant standard or even better post that section up. What is legal in your countries may not be legal in whatever state of Australia the OP lives in.
The relevant standards are probably found within these publications.
AS/NZS 60335.1:2002 , AS/NZS 5762:2005, AS/NZS 5761:2011 , AS/NZS 3760:2010

These all cost money (they should be free!)  so for a small repair such as the OP was talking about it's isn't feasible to thoroughly research this.

So then you have to fall back on having a guess at what is legal.
IMO this equipment would fail test and tag as is(AS/NZS 3760:2010), but would pass if it had an extra layer of insulation of the 'live' parts.
This is why I said it wasn't safe, and so for a customer or friend I would go the extra yard and put the insulation in.

That said if you left it as is, it is still probably safer than crossing the road, which is perfectly legal.

[Nusa]

Except all of those standards you quote are probably too new. If it's from the 1990's, it only has to meet the standards in force at the time of manufacture.

[Specmaster]

Does not mean that it can't or shouldn't be upgraded to the newest standard or indeed improved if its not possible to reach the latest standard does it.

[HackedFridgeMagnet]

Except all of those standards you quote are probably too new. If it's from the 1990's, it only has to meet the standards in force at the time of manufacture.

Yeah good point, but these standards apply now, and in them they probably mention that if the equipment was made under an older standard then the equipment would still be ok if considered 'safe'.
('Safe' is deliberately a loose term. ) At least that is what happens in one standard AS/NZ3000.

But there is also an issue depending on the customer.
If the customer is a business or organisation then it must be tested and tagged to current standards at regular intervals.
IIRC in the OPs case it is a friend.


So I guess for small jobs we are back to make it as safe and legal as is reasonably possible.

[Nusa]

Does not mean that it can't or shouldn't be upgraded to the newest standard or indeed improved if its not possible to reach the latest standard does it.

Unless you are willing to take personal liability when you certify it safe without a certification process, upgrading it may legally be a very bad idea.

[Specmaster]

Does not mean that it can't or shouldn't be upgraded to the newest standard or indeed improved if its not possible to reach the latest standard does it.

Unless you are willing to take personal liability when you certify it safe without a certification process, upgrading it may legally be a very bad idea.

Well in the UK all extraneous metal should be grounded then under those conditions, if the metalwork is accessible by the user without the need for any tools being used then yes, my interpretation is that it ought to be grounded. If it is not touchable under the normal operation then no, leave it.

[Zero999]

Does not mean that it can't or shouldn't be upgraded to the newest standard or indeed improved if its not possible to reach the latest standard does it.

Unless you are willing to take personal liability when you certify it safe without a certification process, upgrading it may legally be a very bad idea.

Well in the UK all extraneous metal should be grounded then under those conditions, if the metalwork is accessible by the user without the need for any tools being used then yes, my interpretation is that it ought to be grounded. If it is not touchable under the normal operation then no, leave it.

Now you're confusing metal cased class 2 equipment, with the fixed electrical installation.

[Specmaster]

Well in the UK all extraneous metal should be grounded then under those conditions, if the metalwork is accessible by the user without the need for any tools being used then yes, my interpretation is that it ought to be grounded. If it is not touchable under the normal operation then no, leave it.

Now you're confusing metal cased class 2 equipment, with the fixed electrical installation.

If the metal case is nothing more then that, a case that surrounds the equipment to keep people from coming into contact with live parts and also forms a cosmetic function, then whats the harm in grounding it?

A cable going to it or another A/V unit or similar could be in contact with the casing and have compromised sheathing, an exposed live conductor could come into contact with the metal work and adjacent to the unit could also be for arguments sake, metal gas fire which must be earthed if the user was to be touching the gas fire and the A/V unit a shock would be the end result???

[Gyro]

Except all of those standards you quote are probably too new. If it's from the 1990's, it only has to meet the standards in force at the time of manufacture.

Luckily for the OP, EN60065 was already in place in the 1990s so his Sony  equipment (as a responsible manufacturer) would clearly have been adhered to. The creepage and Clearances will already be well in excess of the figures tronde keeps quoting. Some liberties have been taken with the mains cable termination, either as a slightly dodgy cost reduction or possibly (given that the wires are soldered to a plug header!) somebody has already been in there and replaced (lengthened?) the mains lead. The original crimped cable socket would have been practically impossible to remove - the inserts are very well fitted in the housing (for obvious reasons) and there are no exposed metal tabs (also for obvious reasons).

Does not mean that it can't or shouldn't be upgraded to the newest standard or indeed improved if its not possible to reach the latest standard does it.

Unless you are willing to take personal liability when you certify it safe without a certification process, upgrading it may legally be a very bad idea.

That my friend is THE VERY CORE OF THE ISSUE, It is the reason for my Red warning to tronde - It is a legal issue.

If you modify the equipment in any way (you can probably justify repairing dry joints or replacing non safety critical components - as long as you re-assemble it in exactly the same way), then you take over the legal responsibilty for its safety.

Companies carry significant public liability insurance - that is not to say that the Design authority and Directors are immune from individual legal liability. If you are repairing stuff for friends then you won't have this insurance. You may be the best of friends, but their home insurance company will most certainly not be your friend if the worst happens.

This is the reason that I restrict the favours I do for friends an neighbors these days to 'taking a look' ("no, sorry, that's not safely repairable") and basic non-critical repairs. I know this specific standard but it's still not worth the risk.

Your point about modification is very well made. In legal terms, you are not competent to make judgements on modifications. As I mentioned in a previous post, even adding additional insulating material, blobbing silicone etc. is changing the flamability characteristics of the product. It could come back to bite you.

My advice to the OP (I think I'm repeating myself here), leave the product exactly as it is. If there was a safety issue in modern terms,then Sony would have recalled it. If you are confident in your abilities, restrict your repair the failed solder joints if they are in a non-safety area (not just the live section, but also anything related to fusible resistors protecting internal rails from overload too).  Basically avoid anything with an 'exclamation mark inside a triangle' in the service manual. Otherwise you could compromise it's flamability characteristics. Then put everything back exactly as you found it. Most service manuals these days include insulation measurements to be carried out on completion of service.

While I have some sympath with tronde's points about breakdown voltage and the laws of physics (which of course I agree with),  the concept of [Edit: "legally unsafe"]  but still "electrically safe" cannot be allowed to stand. The consequences of anything you do in opening and repairing the unit can only be Legal.

I hope this clarifies the issue a little better.

[Zero999]

Well in the UK all extraneous metal should be grounded then under those conditions, if the metalwork is accessible by the user without the need for any tools being used then yes, my interpretation is that it ought to be grounded. If it is not touchable under the normal operation then no, leave it.

Now you're confusing metal cased class 2 equipment, with the fixed electrical installation.

If the metal case is nothing more then that, a case that surrounds the equipment to keep people from coming into contact with live parts and also forms a cosmetic function, then whats the harm in grounding it?

There's no harm in grounding it, just that it's unnecessary.

A cable going to it or another A/V unit or similar could be in contact with the casing and have compromised sheathing, an exposed live conductor could come into contact with the metal work and adjacent to the unit could also be for arguments sake, metal gas fire which must be earthed if the user was to be touching the gas fire and the A/V unit a shock would be the end result???

The gas fire should be earthed, if it's not a class 2 appliance but that's totally irrelevant. It's a different piece of equipment, creating a hazard. One could also argue that earthing a metal chassis can make it more dangerous in certain circumstances, because it will provide a return path for current from a neighbouring piece of equipment who's chassis has become live due to a fault. Touch the earthed chassis and live chassis, on the faulty equipment and receive a potentially fatal shock, if there's no RCD/GFCI to save you. Had the chassis not been earthed, the person would have less chance of a fatal shock, because the current would be much lower.

The above is all irrelevant to the discussion because it involves a fault somewhere else, which is nothing to do with metal cased, class 2 audio equipment.

 

[Specmaster]

I think that where a lot of confusion comes from is the fact that this forum is of an international nature and what may be applicable in one country is not in another and then of course the various countries wiring regulations also disagree with each other in certain countries and these also muddy the waters to an extent.

My point about grounding extraneous metalwork and connecting that metal case of the said Sony (agreed they are a responsible manufacturer) equipment stems from the same argument. In the case of a window it is perfectly feasible for someone to run a power cable via an open window to feed say a lawn mower. The cable could have a damaged sheath with a exposed live cable that could come into contact with an un grounded window frame even as a result of the window being closed onto and cutting into the cable, so someone could then touch at the same time the window frame and something else that was grounded and a possible fatal shock could be received as a result.

Audio and visual gear such as hi-fi separates for example are designed to be stacked on top of each other, each having its own power cable and the way that some of these are connected together can be a right mess, I know from personal experience. It is also conceivable that one or more of these power cables could be routed between the units in some cases and if the cable was in a poor state with the outer sheath compromised and also an damaged secondary sheath on the live core, touching the metal case would mean that at least one piece the A/V equipment would have a case that was at supply potential.

That in its own right, under most conditions is not as dangerous as it sounds until the operator also touches simultaneously say a grounded radiator, or as some else had mentioned, introduces for example a grounded CD player and they happen to be touching that at the same as adjusting volume on the compromised amplifier unit then they could once again receive a nasty shock as a result.

My argument has never in the main been about a fault occurring internally within the equipment, more of an artificially imported one, often by way of something that the owner has done. Sometimes you have to protect the general public from their own actions as in the two incidences I have highlighted the end result should be that the circuit protective device should operate to protect the people in these circumstances.

[hermit]

There's no harm in grounding it, just that it's unnecessary.

And if the end consumer wishes to then there is probably an existing screw that can be backed out and used.  A grounding screw was actually provided on some of this two pronged stuff.

[Specmaster]

There's no harm in grounding it, just that it's unnecessary.

And if the end consumer wishes to then there is probably an existing screw that can be backed out and used.  A grounding screw was actually provided on some of this two pronged stuff.

Well that was my understanding as well and in which case you're back at the same location as I was at earlier in this thread with effectively replacing the 2 core with a 3 core cable and grounding the case. I suppose the difference is that by using the external screw your not modifying the manufacturer's internal connections or their means of entry? Where I have done this myself, I have always replaced the makers cable grommet/gland/clamp assembly with a new one to accept larger OD cable, thus essentially not really modifying their product in a way thats not going to compromise anyone or put anyone at risk.

[Zero999]

There's no harm in grounding it, just that it's unnecessary.

And if the end consumer wishes to then there is probably an existing screw that can be backed out and used.  A grounding screw was actually provided on some of this two pronged stuff.

That grounding point is a place to connect the shields of screened cable, more than anything else. It's not a protective earth terminal. It's there for  EMC purposes.

[Specmaster]

There's no harm in grounding it, just that it's unnecessary.

And if the end consumer wishes to then there is probably an existing screw that can be backed out and used.  A grounding screw was actually provided on some of this two pronged stuff.

That grounding point is a place to connect the shields of screened cable, more than anything else. It's not a protective earth terminal. It's there for  EMC purposes.

How would you do that then? The cables all come pre terminated with suitable plugs, ie., RCA phono or DIN plugs and the shields are already soldered into the plugs?