Have installed a back fed 120V/208Vy-480V delta Xfmr to supply a 480V steam generator (ungrounded). 250.21(4) states I must install ground detectors on this system. Any one know of a source for gound detectors? I am thinking there must be a set up something like a panel surge arrestor
that I can attach at each end of the system?
Haven't been able to google anything up.
Thnx Bman

Go To Erickson by clicking here
Then to the "ground detectors" button on the left

The cheap and simple way is with 25 watt 250 volt lamps.
Take 6 lamps and pair them up in groups of 2.
Series each group then attach one group to each phase . On the other side of the groups
tie those wires together and take them to a normally closed pushbutton. That will act as a lamp test switch ,the other side of the switch connect to ground .

When every thing is normal all 6 lights will glow dim .When there is a ground the grounded phase lamps will go out or very dim and the other lamps will get bright. It is not hitech but it works very well.