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	Subject - Isolated grounds? veganfan At work last night we were installing a couple of robots, and I noticed that all the grounds were green/yellow for isolated grounds. I pointed this out to other electricians, but this did seem to bother them. Now all of these grounds were connected to chassis ground on robots. We just hooked them to a regular grounding conductor. Shouldn’t these be hooked to a separate grounding conductor, or have something to reduce noise hooked to this ground? I mean didn’t we just defeated the purpose of the isolated ground? Ryan_J Yes, you probably defeated the purpose of the IG JimmyDee In the past, I have driven a new ground grid of 4 rods, each 90' long around a robotic machine. To run the conduit to it, we would insert a length of PVC in the down drop to keep all grounds other than the driven grid from the machine. It seemed like overkill to me but we made a ton of money hooking them up this way. The company that manufacturer the machines wouldn't even look at them if they were not hooked up this way. Like Ryan said, you probably defeated what they were trying to do. You probably canceled your warranty as well. Jim Ryan_J Jimmy: I certainly believe you, but isn't it funny how these manufacturer's think ground rods are teh cure all? Mike Delaney I knew an electrician, and his idea of an isolated ground was a three foot piece of green wire inserted in a conduit at each end. Is this correct? lctrc789 Actually, an isolated ground should be just that, isolated from all other grounds and bonding. Article 384-20 exception for isloated grounds. Article 250-146 (d) An isolated ground can run to any ground source (i.e) water pipe, ground rods or any other souce of ground that is isolated from the panel, conduit or any other metallic part of the sysytem. Probably what you have done is what they are saying, if you should have problems with any of this equipment they can come back and say you do not have proper grounds. As far as the green wire in the conduit that doesn't even seem right Pierre Belarge A lot of times when you see a green conductor with yellow stripes, it is for a piece of equipment from another country. It does not mean that is an Isolated equipment Ground. You cannot install a grounding grid for isolated circuits without bonding it to the "system" ground. It is dangerous and not permitted, as a voltage potential could exist between the two grounding systems (Isolated and building systems). The isolated (and insulated) equipment ground conductor is required to be installed with the circuit conductors, it cannot be run 'helter skelter' to ground rods, etc... You can install a "SUPPLEMENTARY" [250.54 - do not confuse this with the requirements for 250.53(D)(2) Supplemental] grounding conductor to ground rods, but it also has to be bonded to the "GROUNDING SYSTEM" . Read 250.146(D) carefully as to the requirements for Isolated grounds. There is a lot that can go wrong with installing Isolated ground receptacles (circuits), this type of installation has lost favor and is not used nearly as much as it once was. Isolating transformers are used more for this type of situation these days. Pierre