I've had kind of bad luck with the SurgeGuard. It quit once, not sure why, and they replaced it under warranty. The second time it quit it shorted out and sparked and made a lot of smoke. It turns out that water had gotten inside and shorted out the innards. We had experienced a lot of rain, but it was not immersed in a puddle so I was not happy about that experience.
We now have the Progressive model and it's working fine, and seems to be better waterproofed than the SurgeGuard was. We never noticed any "humming" from our SurgeGuard. It was the 50 amp model.