Hospital Isolation Panels

[hbendillo]

I have been designing electrical systems for hospitals for a couple of years now after not doing much of that type of work for about 5 years. I had previously done a lot of Health Care design 15 years before that. In my first experience as a young engineer we were still using isolation panels. That practice has been eliminated by most hosipitals due to the fact that flammable anesthetics are no longer used.

One of the young engineers that worked for me ask me how such a panel worked and I told him the phase and neutral conductors are isolated from ground. Basically a direct path back to ground is eliminated. Therefore if a phase is grounded no sparks or explosions. Also, if a patient is grounded, he will not get shocked if he contacts a phase conductor. Am I right on the basic premise? Does anyone have anything to add? Also, is anyone using isolation panels these days?

 

[DanDel]

Isolated power systems are still in use, at least in new construction at Mass General Hospital operating and procedure rooms. Square D Iso-gard systems are currently in use there. I have frequently tested the systems myself.
The basic construction is a 480-240/120V transformer. The neutral on the 240/120V side is not grounded(isolated). At each receptacle, there is a ground, but there is only capacitive coupling voltage potential between the line conductor and ground, and between the neutral and ground. This usually results in a voltage of around 60V measured with a DMM.
The Iso-gard system monitors the current flow to ground in both the line and neutral conductor based on their individual potential to ground. There is an alarm that actuates for currents above 5mA.