That will likely be an issue with the relay, not the pump. All relays can fail and unfortunately yours happened to fail in the on position. It's likely just an unlucky failure. Someone posted a video earlier about cheap relays vs expensive ones and their failures, at the end of the day the cheap relays will almost always be good enough for our purposes but there is always a chance one will fail.
Actually, I changed the wavemaker to another relay and promptly burned that one as well. I have been advised that it is more than likely an inductive load as the wavemaker only draws 1A, but the relay is rated to 10A. I've been advised the following "
[11:46, 8/13/2018] Gaven Marines: If the 220v side then yes I really think that is the problem.
[11:47, 8/13/2018] Gaven Marines: Order a 1N4007 and place across the output of the relay. Make sure polarity correct. Leaded component. Will sort that out 100%"
