Does a isolated ground have to go back to the service ground? I have a MDP/service in a office building basment. The fused switches in the MDP feed MLO lighting panels in different parts of the building. The lighting panels are piped with RMC as the ground, no grounding conductor. Can a isolated grounding conductor just go to this panel? john
isolated ground
- Thread starter jociha
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Re: isolated ground
As far as the NEC is concerned it can stop at any point you choose.
Ideally it goes back to the bonding jumper for the system you are coming off of. That could be at the service or at a SDS transformer if this building has one.
As far as the NEC is concerned it can stop at any point you choose.
Ideally it goes back to the bonding jumper for the system you are coming off of. That could be at the service or at a SDS transformer if this building has one.
Re: isolated ground
jociha, you have asked a good question. NEC does not care where the IG originates, thier primary concern is safety, operation is secondary. From an operational point of view the only place a IG should originate is the N-G bond point of an isolation transformer. Any place else is just a waist of money.
Sorry to repeat your response Bob, just reinforcing your statement.
jociha, you have asked a good question. NEC does not care where the IG originates, thier primary concern is safety, operation is secondary. From an operational point of view the only place a IG should originate is the N-G bond point of an isolation transformer. Any place else is just a waist of money.
Sorry to repeat your response Bob, just reinforcing your statement.
Re: isolated ground
Hello John-
Some additional IG information can be found in a publication entitled "Application Guide for Isolated Ground Wiring Devices", available for free download from the National Electrical Manufacturers Association web site, www.nema.org
The value of the IG wiring method is debatable, and the Institute of Electrical and Electronics Engineers (IEEE) has published several papers on the subject. The problem is that many, if not most, of these IG circuits are wired incorrectly. When we perform PQ site surveys, it is not uncommon to find that the IG and EGC have been tied together in the receptacle box- which offers no noise reduction to the sensitive electronic equipment.
The other problem is the end user thinking some sort of noise filtering circuitry exist in the receptacle. At one department store we witnessed the Corporate IT professional walking around and swapping out regular receptacles with the IG type in locations where computers and cash registers were to be installed. We ended up physically taking one of the units apart to show that no electronics were inside.
You will have to evaluate your own situation, but in some cases you can provide better protection using a traditional receptacle and a plug-in style line filter.
A little more information then you were asking for, but hope this is useful.
Regards,
Mark
Hello John-
Some additional IG information can be found in a publication entitled "Application Guide for Isolated Ground Wiring Devices", available for free download from the National Electrical Manufacturers Association web site, www.nema.org
The value of the IG wiring method is debatable, and the Institute of Electrical and Electronics Engineers (IEEE) has published several papers on the subject. The problem is that many, if not most, of these IG circuits are wired incorrectly. When we perform PQ site surveys, it is not uncommon to find that the IG and EGC have been tied together in the receptacle box- which offers no noise reduction to the sensitive electronic equipment.
The other problem is the end user thinking some sort of noise filtering circuitry exist in the receptacle. At one department store we witnessed the Corporate IT professional walking around and swapping out regular receptacles with the IG type in locations where computers and cash registers were to be installed. We ended up physically taking one of the units apart to show that no electronics were inside.
You will have to evaluate your own situation, but in some cases you can provide better protection using a traditional receptacle and a plug-in style line filter.
A little more information then you were asking for, but hope this is useful.
Regards,
Mark
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