I have had much experience in industry with similar locations. Here are a few tips: -NEMA doesn't rate for condensation. A NEMA-1 box is preferable to an undrained NEMA-3 or -4(hosetight) box, as the condensation WILL accumulate. I've seen boxes with over an inch of condensate in them. -Water will also enter conduit and condense, and settle, in low spots. THHN is not suitable for these wet locations. -Corrosion of terminals and connections can be prevented with NOALOX. Commercial anti-seize is often used, but is not technically listed for this use; Noalox is. Apply the Noalox also to conduit fittings, etc., to prevent their rusting-up as well. -Finally, this application is not as scary as it looks. Not only does water have a place to drain, but it is typical in Europe for the 220V water heater to be hung within the shower enclosure. While I wouldn't have a panel inside a shower, I also know that panels are often placed in industrial areas that are even wetter, and more subject to condensation and corrosion!
