Hi I posted earlier but have more information. The house we purchased was previously wired for a spa on the deck. Always having wanted a spa we found a used one and put it out to the deck. It sits about 70ft from the main panel. Opening up the disconnect box there was a disconnected 40 amp gfci and the following wires coming from the main panel, two black #8's, a #12 white, #12 Green and #12 red. Being a little confused by 5 wires coming to the disconnect I opened the main panel and found that the red was taped off and not connected to anything. I am wondering if I can run the spa with the wiring that currently exists? If my neutral also needs to be a #8 is it possible to utilize the red wire and attach it to the neutral in the main and the disconnect in addition to the current neutral? As you can tell I am hoping I don't have to pull out the current wiring and rewire. It is all THHN wiring

your common wire should be a #8 or least a #6 but it really depend on your amps on the hottub what you could do when you hook it up check out how many amps by using a ampmeter on the motor which you will have to look to see how many amps your motor needs which the spec's should be on the motor and if its using less amperage which you could start burning up a motor or a relay