I have installed many of these outdoor units and have never ever seen a set of manufaturers instructions that said anything other than must have gfci protection. My understanding of the code says that they all require it as wel. no hotub or spa we have ever installed in any or our myriad inspection jurisdictions would ever accept an install without gfci protection. Hmmm lets see i wanna jump in a pool of water that is being circulated by and electric motor driven pump which may just have a winding that is partially grounded? Not enuf to trip a breaker but leaking current into the water neverthless? The guy that never has put a gfci on on of these can jump in there if he wants,NOT ME!!!