pool heater

Hi forum, Firstly apologies if the wrong terminology is used, I will clarify if needed. Can I install a normal 3 pin plug where a fused spur once was, for a pool heater? detail below: I have a redundant 13A fused spur which was previously used for an old electric heater*. I have recently...

I've always just assumed that the colder the return to the boiler the more efficient the boiler would be (i.e. greater differential so heat transfer through manifold is faster). But I've come across direct evidence to the contrary (e.g. boiler recommends minimum 60 degree return, 'hearth' temp...