Re: THW in Operating rooms????
Scott, if you are talking about O.R.'s served with isolation power systems, this would be XHHW for it's dielectric constant. Manufacturers require this in their information with the isolation system equipment.
The NEC doesn't directly state XHHW, but does recommend a dielectric constant of 3.5.
Read 517.160, specifically 517.160(6) and the FPN's.
Roger