This restaurant that I do electrical maintenance for has become quite an obstacle course. It was built less than two years ago and I would have hoped that everything would be fairly easy. Not so much.
They have an outdoor bar area where they have multiple POS terminals (cash registers). When the place was built, they put in a really nice centralized UPS setup with a separate panel to feed dedicated circuits to each of these terminals (there are 24 of them). They all have (gasp) isolated ground receptacles.
The problem is that the ones outside are on standard IG receptacles with in-use covers. UPS or not, these receptacles obviously have to be GFI protected. For this reason, I've told them that they can't use the standard IG receptacles that were installed outside. Frankly, I don't know how this setup passed inspection anyway, but that's another subject.
I'd like to offer them a solution in order to legalize these outdoor receptacles. My thought was to just replace them with GFI receptacles and be done with it, but their rocket scientist IT manager at corporate has mandated that all POS terminals must be on IG receptacles. I've never seen an IG/GFI receptacle. When I was at the supply house today, I asked the counter guy about them and he looked at me as if I had three eyes.
Is there even such a thing? I suppose that I could change out the four breakers to GFI ones, but the panel is a bolt-in Cutler Hammer one. I can only imagine how much those breakers would cost. Any ideas?
Put a dead front GFCI in the out building in front of the IG?
I agree the IT manager is living in the 70s. IBM lifted the IG recommendation in the 80s for "noise". Done properly it might help with lightning mitigation tho but you would have to do it with that in mind and lay it out right.
John, the IG only means that the isolated grounding conductor does not land on anything else before it gets to the receptacle and it doesn't hit the box there. On the line side it still gets connected to the service grounding system, typically on the bus par where the MBJ lands.
If I was doing this for lightning mitigation, I would land all the IGs on a bus bar, as close to the server as possible so it was acting as a bonding conductor between the server and all of the terminals. Then go back to the MBJ bar from there.
In my pool bar situation here, we actually fixed the lightning problem with a frame to frame bonding conductor from the remote POS terminal to the server, pulled as short as we could get it, with ferrites on the data cable, left long. We lived with the "ground loop" guys and the "noise" guys all summer, until we pointed out the terminal did not get blown up once or twice a month like it was.
I saw a lot of strange stuff in the computer biz but I was a IAEI 2a, 2b, 2c at the same time that I was doing installation planning at IBM so I did try to be sure everything was compliant.
Even then the "official" description of the IG circuit had it landing on the ground electrode system of the service, usually in the service disconnect enclosure on the main grounding bus where the MBJ was. I may still have the IBM physical planning manual around here somewhere.
You could always get a fight started with a "noise" guy about whether building steel was really a grounding electrode. Occasionally I did find a guy who wanted a separate ground rod. I could usually make that idea go away using a current probe on a scope.
Greg: Back many years, I remember a data room job with an IG. An insulated 'IG' terminal block within a subpanel, #4 'IG' to three rods at exterior of bldg. The 'IG' terminal block was a recycled neutral bar. THe branch circuits were 14/4 BX. The guy I worked for way back then was a real butcher.
Generally the IG was on neutral bar because they didn't extend the neutral to the computer room panel. All loads were L/L. The IG The IG was basically the neutral conductor from the service or transformer, taped green instead of white. That was where you had the fight about tagging building steel in the computer room panel.