big john
Senior Member
- Location
- Portland, ME
First things first, I've never found a good answer for this:
A) What introduces noise into a ground line in the first place? Is a lot of it contributed by the fact that devices with a lot of solid-state elctronics [computers, copyers, etc.] use the ground as a voltage reference and this contributes to the ambiant noise? Are larger transients caused by the EMI that accompanies the operation of motors, compressors, etc.? If so, would this not also carry down the line conductors to affect any ground not in the proximity of the motor/compressor but run parallel with the line conductors?
B) Assuming at least some of the above is correct wouldn't it make the most sense to run a dedicated circuit with an isolated ground to help eliminate noise introduced by the line conductors? Is it not contrary to the whole idea to run a "clean" ground in along side "dirty" power?
C) Why, in a wood-frame house wired in Romex, is it said that IGs are a waste? If any of the above is true, then certainly devices in the average home from dishwashers to blenders have the potential to introduce noise into the ground line.
D) What makes a steel frame building so different than a wood frame house? Is it because the framework can almost act as an antenna of sorts and will transmit any EMI it picks up via the framing members into the metal boxes to the EGC? If that is the case, wouldn't it do just as much good to simply put recepticals in plastic boxes when mounted to metal studs? Or would you sacrifice some shielding provided by the grounded box?
E) What power quality problems would arise from having two clean interconnected devices on the same circuit but connected to two different IGRs? E.g.: Two computers only connected to each other, no printers, scanners, etc. Would, in this case, the problem not be power quality but the concept that the datacom cable connecting the combuters could conduct fault current if any difference in potential between the grounds developed?
F) It is often said that IGs are mostly installed to do away with common-mode voltage. Try as I might, I can't find a simple explanation of what this is or is even caused by. Any links or ideas?
G) On top of all this, from reading Awwt's recent question and one of Derek's replies CMV is best eliminated not by an IG but by an isolation transformer.
If this is the case under what circumstance would a IG even be necessary? You can not use them on clean equipment interconnected with dirty equipment, which right away eliminates almost all computers. Is it only truely effective to install an IG to a piece of equipment that is completely stand-alone, introduces minimal noise into the line, and needs a clean ground? If this is the case, shouldn't IG installations be limited to dedicated laboratory equipment or similar?
Anything else you'd like to add, feel free.
Many thanks.
-John
A) What introduces noise into a ground line in the first place? Is a lot of it contributed by the fact that devices with a lot of solid-state elctronics [computers, copyers, etc.] use the ground as a voltage reference and this contributes to the ambiant noise? Are larger transients caused by the EMI that accompanies the operation of motors, compressors, etc.? If so, would this not also carry down the line conductors to affect any ground not in the proximity of the motor/compressor but run parallel with the line conductors?
B) Assuming at least some of the above is correct wouldn't it make the most sense to run a dedicated circuit with an isolated ground to help eliminate noise introduced by the line conductors? Is it not contrary to the whole idea to run a "clean" ground in along side "dirty" power?
C) Why, in a wood-frame house wired in Romex, is it said that IGs are a waste? If any of the above is true, then certainly devices in the average home from dishwashers to blenders have the potential to introduce noise into the ground line.
D) What makes a steel frame building so different than a wood frame house? Is it because the framework can almost act as an antenna of sorts and will transmit any EMI it picks up via the framing members into the metal boxes to the EGC? If that is the case, wouldn't it do just as much good to simply put recepticals in plastic boxes when mounted to metal studs? Or would you sacrifice some shielding provided by the grounded box?
E) What power quality problems would arise from having two clean interconnected devices on the same circuit but connected to two different IGRs? E.g.: Two computers only connected to each other, no printers, scanners, etc. Would, in this case, the problem not be power quality but the concept that the datacom cable connecting the combuters could conduct fault current if any difference in potential between the grounds developed?
F) It is often said that IGs are mostly installed to do away with common-mode voltage. Try as I might, I can't find a simple explanation of what this is or is even caused by. Any links or ideas?
G) On top of all this, from reading Awwt's recent question and one of Derek's replies CMV is best eliminated not by an IG but by an isolation transformer.
If this is the case under what circumstance would a IG even be necessary? You can not use them on clean equipment interconnected with dirty equipment, which right away eliminates almost all computers. Is it only truely effective to install an IG to a piece of equipment that is completely stand-alone, introduces minimal noise into the line, and needs a clean ground? If this is the case, shouldn't IG installations be limited to dedicated laboratory equipment or similar?
Anything else you'd like to add, feel free.
Many thanks.
-John