I have a swim spa that I recently purchased about 15 yrs old. Still need to wire in. I am going to install a 100amp sub panel on the back porch. Wire to a disconnect within 5' line of sight from spa with the GFI breaker. Currently I have 4 pumps, lights etc. How do I size the disconnect to handle the load. Aprox 25ft from sub panel to disconnect. Will be using a Ng boiler instead of Kw heater. Any suggestions would help. Thanks
As per the 2011 NEC, the disconnect CANNOT be within 5' of the inside wall of the hot tub.
With that said, wiring a hot tub is not a good DIY project. There are a number of code issues that you will have to adhere to. Items such as metal type siding, downspouts, gutters. Also, there may be requirements as to GFI protecting existing lights and outlets within a certain distance from the hot tub.
By the very nature of pools and hot tubs, I would not recommend a homeowner taking on the wiring of such items.