Isolated ground for elevator

[gburch@ameritech.net]

My client is installing new elevators in an existing highrise building. The elevator equipment supplier is requesting an isolated ground. The existing feeder equipment ground protection is via the conduit system. Installing a isolated gound in the existing feeder is not an option.
Is it within the NEC to provide an isolated ground conductor run seperately from the circuit conductors back to the main service ground?
Or is an isolation transformer the option? [LIST] :confused:

[websparky]

Hi,

At first glance, there does not seem to be an approved method for running an isolated grounding conductor separate from the phase conductors.

Maybe someone else here will chime-in!

Have you considered asking your AHJ about running one in a separate non-metalic raceway?

Hummm......

[ron]

The only reference that I can find in the NEC for isolated ground is regarding receptacles. Even the reference for recepts indicates that it must be run with the circuit conductors.

[brian john]

Better yet ask the equipment supplier WHY?????????

Duh! cause we did it on the last job without any problems.

[roger]

I have observed that in general, elevator designers are like medical equipment designers, (G* medical and Ph*ll*ps in particular) they hear of something (iso grounds) and think it's the best idea since air. It doesn't have any thing to do with the integrety or operation of the equipment.

FPN: my opinion is not necassarily that of others. (unless they deal with these people regularly) :D

Roger

[bennie]

I don't know if it has anything to do with the touch type floor selectors or not.

[bwyllie]

Haven't heard of an isolated ground for the elevators but have heard of an Equipment Ground Conductor now being required, in other words the elevator people do not want the conduit being used.