I think not. NM is not one of the approved wiring methods in 680 part II. I also could have problems with the ampacity, based on the nameplate rating of the spa and mfg instructions. 8ga is only good for 40a in the 60c column.
Re: 50 amp hot tub#94072 07/06/0507:16 AM07/06/0507:16 AM
Shorties right read your Manufacture's manual most spa manufacture's will put min. wire size and I've found more times tahn not it is a #6 copper, but check your manual. If customer doesn' know call dealer they bought it from.
Re: 50 amp hot tub#94077 07/06/0506:38 PM07/06/0506:38 PM
A spa is a combination load with a significant part that is a "toaster wire" heater. The answer is in the manufacturer's instructions unless you want to start reading nameplate ratings and calculating. You are still stuck in the 60c column with Romex.