Sheilding, EMC shielding in fact.... No ground connection required...
To further fuel the flames, only a COMPLETE IDIOT would leave dangerous voltages open without a proper cover in their equipment for normal use... All dangerous voltages should be enclosed in a grounded metal case for DIY projects, ALL projects there are no exceptions to this rule, safety first. If you do not do this you should not be playing with electricity especially mains voltages.
Wake up my friend, i was talking about plasma HF start. Your shielded PC if not GROUNDED will skip a beat in its heart when i start the plasma.
But did you read about Spain's electrical codes?Boyan Silyavski said:
In the UK mains safety comes mainly from equipotential bonding. Introducing an extra 'ground' into this can have effects varying from fairly harmless to extremely dangerous, depending on exactly how the local distribution is wired. Spain may or may not be similar.
In the UK mains safety comes mainly from equipotential bonding. Introducing an extra 'ground' into this can have effects varying from fairly harmless to extremely dangerous, depending on exactly how the local distribution is wired. Spain may or may not be similar.
Sorry, but Equipotential Bonding has a completely different purpose from earthing. Very simply, the earth cable is there to make sure that during a fault enough current will flow so as to trip the mcb or blow the fuse.
Eq Bonding is there to ensure that during a fault all metalwork in contact with (planet) Earth will be at the same voltage, so if you were to touch two metallic surfaces simultaneously you would not feel anything let alone get a shock.
I'll try and find some authoritive but easily understood links for this 'cos as you say electricity is very dangerous
All the best
Drew
Sorry, but Equipotential Bonding has a completely different purpose from earthing. Very simply, the earth cable is there to make sure that during a fault enough current will flow so as to trip the mcb or blow the fuse.
Eq Bonding is there to ensure that during a fault all metalwork in contact with (planet) Earth will be at the same voltage, so if you were to touch two metallic surfaces simultaneously you would not feel anything let alone get a shock.
I'll try and find some authoritive but easily understood links for this 'cos as you say electricity is very dangerous
All the best
Drew
Read your post, you wake up to what you said, shielding when in fact you are talking about creating a spike on the mains when your plasma torch fires up, get the facts straight first.....
No. It is equipotential bonding which ensures that enough current will flow under fault conditions to trip the breaker. It also ensures that everything which we expect to be at '0V' are all at the same voltage, so you can't get electrocuted by touching two of them at the same time. Whether the equipotential is connected to the ground outside is a separate issue.drewan said:
Some UK houses use PME, in which (if I understand it correctly) the 'earth' wire (and hence all bonded items) are connected to the incoming mains neutral. In this case adding an external 'ground' will reduce safety.
Microphone cable is balanced, therefore AES EBU was his only choice to test the digital cable for analog signal use...
PLEASE READ Earthing and Bonding | Electrical Safety First or
What is the difference between Bonding, Grounding and Earthing? | EEP
just two of hundreds of pages on Google.
Also I would think most of the UK is PME, (EDF say all of their area is), which you are right is where the earth and neutral are connected at the incoming service head, NOT the consumer unit/fuseboard. PME stands for Permanent Multiple Earth and no, the adding of an additional earth stake, (done properly) will not lessen safety in any way, and is sometimes a good idea.
That is not my understanding.drewan said:
No. PME means Protective Multiple Earth - see http://rsgb.org/main/files/2012/06/emc-leaflet-07.pdf. This notes that adding extra 'grounds' needs to be done correctly to avoid adding extra hazards under fault conditions. If done badly (e.g. no proper bonding to other 'earths') then it can make things worse. This is because under certain fault conditions the 'earth' of PME can be nowhere near local ground potential.
The first link you gave does not understand earthing. It was written for (and possibly by) people who don't understand electricity. The second one is not much better. They confuse 'earth/ground' with 'the reference potential/conductor to which everything is bonded'. This may be because they have the newbie confusion that thinks of 'a voltage' rather than a potential difference.
If I may...
Bonding is the metallic connection between different conductive items. By NEC, it's purpose is to assure that exposed metal surfaces which may be touched by humans cannot exceed 50 volts in the event of a fault between the metal surfaces and the hot conductor of the line.
During a fault, typical (US) breakers are rated to survive 10 kiloamps. To assure bonding can do it's job, it must be able to survive that level (for connections close to the load panel), and several kiloamps if the outlets are farther away. All this while maintaining less than 50 volts on the touchable surfaces.
Earthing is the use of a conductive rod, typically 8 feet or so, into the dirt such that in the event of a lightning strike, the current will have a reasonable path to follow. Per NEC, when one rod is used, it MUST have a resistance value of less than 25 ohms. If it is greater than that, a second rod must be installed. Note that after a second rod is installed, there is no further resistance requirement.
An earthing rod at or near 25 ohms will NOT provide a connection capable of preventing lethal voltage at exposed surfaces. At it's worst, it would only allow less than 4 amperes to be drawn from the hot during a fault, and standard circuit breakers will NOT clear the line. The result would be a permanently energized surface, definitely lethal.
This warrants repeating: do not UNDER ANY CIRCUMSTANCES!!!!, rely on earthing to trip a circuit breaker!!!!! NEVER.
The first link you provided, DF96 is absolutely correct, it was written by someone who does not know code.
Multiple earthing rods may not increase the electrocution hazard, but it will absolutely increase the possibility that any electronics which is tied to both by some obscure path, will be fried in the event of a direct strike, a nearby strike, or sometimes even a cloud to cloud bolt.
John
The first link is terribly incorrect!
The second like is not much better, but some of it may be translation problems.
That's a bit vague (first three words) and surely not exactly what you meant. Code is pretty clear on that. If you could clear that up it would be great. Thanks.
The rest of the post was excellent and very clear. It explains what grounding will and will not do, which most people don't understand. It's the bonded neutral that provides most of the protection.
I think what is meant:
If there is a 'separate' ground rod (one that is not part of the main earthing system) and if some components are connected to this 'separate' ground while the remainder of the hi-fi is referenced to the main earth. And if there is a interconnect or data cable between these two areas. Then a nearby lightning stroke could develop thousands of volts between the two areas. But they are connected by the interconnect cable.
If there is a 'separate' ground rod (one that is not part of the main earthing system) and if some components are connected to this 'separate' ground while the remainder of the hi-fi is referenced to the main earth. And if there is a interconnect or data cable between these two areas. Then a nearby lightning stroke could develop thousands of volts between the two areas. But they are connected by the interconnect cable.
Basically, yes. If you connect 2, 3, 4 ground rods together as a unit, going thru a single ground wire to the main grounding point, that's perfectly fine. IIRC, code says they should be spaced by 6 ft, but I'd need to check on that. The multiple rods act as a single ground of low resistance.
What is not liked, and not permitted in residential use in the USA, is a separate grounding point. That means something like having a ground rod at one end of the house and another rod at the other end of the house tied in separately. That's a no-no. I've done it, and called it a "technical ground" - but it's not code and can cause problems with lightening strikes, as you mention.
Somewhere I have a nice PowerPoint presentation by a fellow that writes and consults for the NEC (National Electrical Code). He does a good job of explaining grounding, bonding and safety. He gave permission to post it here, but I have yet to do so (too big to attach).
What is not liked, and not permitted in residential use in the USA, is a separate grounding point. That means something like having a ground rod at one end of the house and another rod at the other end of the house tied in separately. That's a no-no. I've done it, and called it a "technical ground" - but it's not code and can cause problems with lightening strikes, as you mention.
Somewhere I have a nice PowerPoint presentation by a fellow that writes and consults for the NEC (National Electrical Code). He does a good job of explaining grounding, bonding and safety. He gave permission to post it here, but I have yet to do so (too big to attach).
Speedskater is dead on in his explanation.That's a bit vague (first three words) and surely not exactly what you meant. Code is pretty clear on that. If you could clear that up it would be great. Thanks.
There are a few things that require mentioning. The definition of terms here can be complex, and for grounding and bonding, it is VERY easy to mis-interpret what is being said.
The NEC calls the connection to the earth "grounding", and it is done by means of a "grounding electrode". NEC does not use the term "earthing", yet most will use that term to denote a method of connection to the earth, or dirt.
The NEC does NOT use a connection to "earth" as one suitable for forcing a breaker to open in the event of a fault.
NEC uses the term "bonding" when referring to the electrical connection between two metal parts.
When NEC mentions two grounding electrodes, they state that they must be at least 6 feet apart. However, they must be tied together and they are called a common grounding electrode.
NEC 2008 250.54 states : ""but the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4). (both of those cites actually say the exact same thing).
John
Doesn't diyaudio.com also have rules covering safety in designs and what can be posted regarding safety, transformers, etc.? Or am I thinking of another site? If so, probably a must read for beginners and experienced folks.
It IS diyaudio that has safety rules regarding posting, I recall that old-fashioned no-power-transformer line-powered schematics are verboten for safety reasons.
Here's the page and relevant quote, and I've bolded the most relevant part. The rules have no mention of electrical building wiring, so it would be up to a moderator to make a ruling on this thread:
The rules | diyAudio Helpdesk
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