Why is it so hard to understand
- Thread starter roger
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K8MHZ
Senior Member
- Occupation
- Electrician
For clearing faults, multiple parallel paths and loops are no issue.
Multiple parallel paths and loops may, however, cause problems with audio and radio installations. In radio, we try to use a 'single point ground' system. That's not self explanatory. But in a nutshell, we try to do away with as many parallel grounding paths and loops as we can. I heard the same is done on audio systems, but that's not my thing.
Multiple parallel paths and loops may, however, cause problems with audio and radio installations. In radio, we try to use a 'single point ground' system. That's not self explanatory. But in a nutshell, we try to do away with as many parallel grounding paths and loops as we can. I heard the same is done on audio systems, but that's not my thing.
cuba_pete
Senior Member
- Location
- Washington State
Depending on the frequencies of interest, yes, both radio and audio can benefit from a properly bonded/grounded single-point ground system.
I have an extensive system that I have to explain to PE's, EE's, and sparkies pretty regularly. Some see the IG receptacles and immediately call witchcraft...having no idea how to implement any of the basic methods in the Green or Emerald books at all.
All of my "engineering" experience came from working on the same equipment for about 28 years now. I am an electronics technician by paygrade, but engineer by job title.
- Location
- Massachusetts
IG is voodoo 99% of the time and is generally compromised soon after installation.
JFletcher
Senior Member
- Location
- Williamsburg, VA
We're not talking about supplementary (ie, not code required) ground rods are we? I was watching a MH video where he was showing that driving an extra rod, say at a generator, or for a PV array, could fry the electronics in event of a lightning strike. Lightning hits earth, travels up the ground rod at the generator/array, thru the circuitry, then back to the ground at the service.
Carultch
Senior Member
- Location
- Massachusetts
So what exactly are we supposed to do with 690.47(D)anger? Put in the counterproductive superfluous electrode anyway, and then disconnect it after you get your approval?
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
You do what the code requires and tell the customer that good insurance is the only real protection against lightning damage.
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
They are connected as a system Roger
How our NEC system is configured via art 250 is where most sparks end, because this is what we are trained to do
Unfortunately said manual forwards little on theory , in fact even soars expands very little on the theory of how GEC & ECG coexist.
This is why i encourage the study of other earthing systems. I've also found the better engineers dwell on comparative analysis (as opposed to those all engine, no ears) from this objective stance , vs. the subjective constraints of nec offerings.
~RJ~
Everybody understands that Steve however, you can have either without the other and they would perform their intended functions the same.
With that said, let's do away with earthing in this thread and concentrate on a low impedance path to the source.
This low impedance path's intended function is to clear faults and a path consisting of multiple loops of conductors, conduits, pipes, metal framing, etc ... (the more the merrier) is a good thing.
Roger
With that said, let's do away with earthing in this thread and concentrate on a low impedance path to the source.
This low impedance path's intended function is to clear faults and a path consisting of multiple loops of conductors, conduits, pipes, metal framing, etc ... (the more the merrier) is a good thing.
Roger
- Location
- Illinois
- Occupation
- retired electrician
I though that term referred to a single point of connection between the GEC, EGCs and the grounded conductor(s) and not to parallel paths in the equipment grounding system. Such paths are almost impossible to avoid unless you take special care in the design and installation of the system, especially where you are using wiring methods that are metallic and connecting to equipment with metallic cases.
K8MHZ
Senior Member
- Occupation
- Electrician
Good point. SPG does mean different things to AC mains power and audio/radio set ups. SPG in audio/radio means attempting to bring all equipment chassis grounds to a single point, preferably with the same length conductors, and doing so without violating NEC grounding requirements. It is an attempt to best eliminate all loops in the chassis grounding connections, which is easier said than done. Audio/radio SPG is not done for safety, like NEC SPG, instead it's done to attempt to eliminate current flow at audio/radio frequencies on the grounding conductors which may cause noise or RF burns.
Brian Dang
Member
- Location
- Burbank, Ca, US
https://en.wikipedia.org/wiki/Ground_loop_(electricity)
“[FONT="]If A and B are simple electricalapparatus, the signals between them being of a simple nature, such as 24V DC tocontrol relays, this ground loop is harmless and merely reinforces thegrounding system, such that, if for example, B develops a fault causing itsmetalwork to become live, in addition to its own protective ground conductorthere is an additional path to ground via A, so the momentary rise in potentialbefore the fuse or circuit breaker operates to remove power will be reducedsomewhat, improving safety.[/FONT]
[FONT="]However,if A and B are electronic apparatus such as parts of an audio system, or acomputer system, the signal(s), typically in the region of millivolts to a fewvolts, passing between them will be vulnerable to corruption.”[/FONT]
[FONT="]It’s very common in electronic system,including audio system, to have the circuit board ground (low voltage circuit systemground, not the AC green wire EGC) connected to the device chassis. In thiscase, when there is a ground loop current (by multi- EGC paths in the ACdistribution) then this ground loop current create different voltage potentialon different audio equipment, or different system ground voltage on theinterconnected equipment, which leads to noise or hum (a 1V audio signal from pre-ampA becomes 1.2V (distorted) in recorder B).[/FONT]
[FONT="]So it is depending on the purpose:for a normal AC power distribution, a multiple ground paths for fault clearing isdesirable, but this could lead to negative effects if the site has sensitiveelectronic equipment, e.g. computers or audios. For a communication company, doyou want to buy a building with multi-path EGC for fault clearing?[/FONT]
“[FONT="]If A and B are simple electricalapparatus, the signals between them being of a simple nature, such as 24V DC tocontrol relays, this ground loop is harmless and merely reinforces thegrounding system, such that, if for example, B develops a fault causing itsmetalwork to become live, in addition to its own protective ground conductorthere is an additional path to ground via A, so the momentary rise in potentialbefore the fuse or circuit breaker operates to remove power will be reducedsomewhat, improving safety.[/FONT]
[FONT="]However,if A and B are electronic apparatus such as parts of an audio system, or acomputer system, the signal(s), typically in the region of millivolts to a fewvolts, passing between them will be vulnerable to corruption.”[/FONT]
[FONT="]It’s very common in electronic system,including audio system, to have the circuit board ground (low voltage circuit systemground, not the AC green wire EGC) connected to the device chassis. In thiscase, when there is a ground loop current (by multi- EGC paths in the ACdistribution) then this ground loop current create different voltage potentialon different audio equipment, or different system ground voltage on theinterconnected equipment, which leads to noise or hum (a 1V audio signal from pre-ampA becomes 1.2V (distorted) in recorder B).[/FONT]
[FONT="]So it is depending on the purpose:for a normal AC power distribution, a multiple ground paths for fault clearing isdesirable, but this could lead to negative effects if the site has sensitiveelectronic equipment, e.g. computers or audios. For a communication company, doyou want to buy a building with multi-path EGC for fault clearing?[/FONT]
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
A 'ground loop' can be rather hard to mitigate, considering the construction methods of M.E.N. and S.D.S. 's prevalent to most American industry. Best examples are Cat 5e trunk lines, remote VFD & PLC's entering such structures all doomed from the start to sensitivity problems inherent in said design.
From your link>
Our NEC approach , which arguably dictates it's own art 250 violations>
~RJ~
From your link>
Our NEC approach , which arguably dictates it's own art 250 violations>
~RJ~
- Location
- Illinois
- Occupation
- retired electrician
I don't understand. I work in a plant that has all of those things operating without issues and there are hundreds if not thousands of parallel paths for the EGC.
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