I have been back through several threads looking for a picture in reference to proper grounding of seperately derived systems. I understand 250.30, but have trouble at times explaining. I have seen some good pictorials of the proper bonding/grounding for a sds system which would help me in my enforcement. If someone has a pic handy that they could post here, it would be appreciated.
sep. deriverd system grounding
- Thread starter augie47
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LawnGuyLandSparky
Senior Member
roger said:Here's another.
Please note that these illustrations are property of Mike Holt Enterprises. Go to this page for more info.
Roger
This cracks me up. On a large project for a particuliarly touchy customer with money to burn, "isolated grounds" were the norm rather than the exception. Picture that transformer times 20, and that panel times 80, and tons and tons of cubicles, raised computer floor outlets, multiple studio lighting and dimming systems, and robotic cameras. "We want everything to have an isolated ground." 2 insulated grounding conductors were pulled in every raceway. Sometimes more as "we don't want grounds for one circuit shared with grounds from another circuit just because they're in the same raceway."
Now I ask, where in a Manhattan office tower is one to find an "isolated ground?
In the end, every neutral, ground, and isolated ground ended up landing on XO.
- Location
- Massachusetts
LawnGuyLandSparky said:
There is no other choice, the IG is required to land back at XO of the SDS or at the services MBJ.
It can not get more 'isolated' than that without violating the NEC and being a shock hazard.
back to the xo
back to the xo
correct me if I am wrong but can't you just run a single isolated ground from the xfmr gound along with the normal ground and connent it to a isolated ground bus and land all you isolated grounds on that bus in the panel and route a single isolated ground conductor to the xfmr???
back to the xo
correct me if I am wrong but can't you just run a single isolated ground from the xfmr gound along with the normal ground and connent it to a isolated ground bus and land all you isolated grounds on that bus in the panel and route a single isolated ground conductor to the xfmr???
brian john
Senior Member
- Location
- Leesburg, VA
The isolated ground if required by a customer as part of the job specifications starts at the same place and as the SDS un-isolated ground, XO. The installer just sets two ground termination bars in each distribution panel or fused safety switch from that point on. A standard/dirty/contaminated ground that is bonded to he back box and a second ground termination bar that is isolated from the distribution equipment, with insulated conductors.
The thought by some (engineers, electricians, manufactures, supplier, installers and teachers of the trade, ECT.....) that there is some MAGIC place where we can come up with this supposed ISOLATED connection to Earth where all the dirty electrons go when they are bad, does not exist.
The thought by some (engineers, electricians, manufactures, supplier, installers and teachers of the trade, ECT.....) that there is some MAGIC place where we can come up with this supposed ISOLATED connection to Earth where all the dirty electrons go when they are bad, does not exist.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Mike01 said:
I'll correct you, yes you're wrong. This is a very common way to design IG systems. The IG ground is connected to the same point as the bonding jumper between the transformer case and the neutral and is kept isolated from that point through out the IG system.
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