On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply


On a "floating" mains supply as described you have to fuse both poles
(I'm calling them A & B rather than L & N) at the transformer secondary
for safety (there could be a transformer fault). Now, consider an earth
fault after the fuse on pole A. Pole B is now at line voltage to earth
because neither fuse will blow (there is insufficient current to earth on
pole B). In this situation it's very easy to get a fatal shock from pole
B to earth. A second earth fault or overcurrent, now on pole B, will blow
one or both of the fuses - but it's anyone's guess which one as they will
have to have the same rating. Now, is the supply earthed or not? Which
side is live to earth (if either)?

This sort of system is possible (it is actually used in some specialist
situations).