Hello,

I have a 240 volt hot tub to hook up and have a few questions. I have about a 120' total run from the main disconnect and planned on using 6/3 NM-B from the main through the interior of the house to the GFI Spa panel outside, then about #6 THWN to the tub itself.

This is where I'm a little confused. Its about 65' from the main to the basement wall that goes under my deck, then another 10' under the deck until where the Spa disconnect will be located. I was under the impression that I cannot run the NM-B wire in conduit the last 10' under the deck because that is only rated for interior use. So what can I do to keep it legal and up to code between the basement wall and the Spa disconnect under the deck?

Thanks.

First question is, "What is the amperage draw of the hot tub".

Over 100' you should take voltage drop into consideration.

Manufacture suggests a 50 amp breaker; it's a 40 amp draw on start up with pumps and heater running.

The NM-B would run to the inside of the exterior wall, to a junction box. From there ridged conduit with #6 THWN would run out the wall and to the Spa disconnect (I'm slightly concerned here. You say a total of 120', and based on your numbers, the Spa disconnect is 45' from the spa. The Spa disconnect MUST be visible from the spa, and some municipalities have a limitation as to how far away it can be).