Also bear in mind, they are center-tapped earth on the secondary, so do not try to bond earth to neutral...[/b]
I would NEVER do that, except in ONE place. If, and only IF, you get your feeder from the utility company as a 3 phases plus PEN, which I do, there is a point in the fuse panel where Neutral busbar and Ground busbar are joined. PEN is connected adjacent to this point, and further out in the network,
blue and
green/
yellow never mix.
Further, as a principle, I treat phase and neutral as
live conductors in ANY single-phase situation. That way, I never ever have to bother with polarity. Our plugs (we're on the same standard as Germany, i.e. Schutzkontakt CEE7/4 and europlug CEE 7/16) aren't polarized, so as soon as one's used an extension cord or a multiple outlet, polarity is stochastic.
Bonding the center-tap on the transformer secondary is both possible and (looking at security) desirable. Also serves to teach the poor uneducated about both poles of a mains flex best being regarded as dangerous.