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Our 23 year old hot tub finally gave out so we are having a new one delivered but were told it needed a 60 amp breaker. When checking the panel I saw that the old tub used a 50 amp breaker. How do I determine if the wiring is safe to use with a 60 amp breaker? The current wire used is very big but I want to be sure.

The length needed for the run is 100'; 75' from the breaker box to a disconnect on the deck and then another 25' from the disconnect box/switch to the tub. The current wire is marked "Essex 8-SG non metallic sheathed cable Type NM-B 600 volt E-10816-K (UL)".

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Number 8NM cable is not good for 60A. To be honest it was not even good for 50a. #8NM cable is only good for up to a 40A circuit.

For a 60A circuit you need #6cu or better yet #4 considering the distance.

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If your hot tub is outdoors, NM-B cable is not rated for outside use. It's for indoor use only.

You'll need to buy THHN or UF rated cable. THHN is bought as a single wire, so you'll need 2 #6AWG for the hot (assuming 240v) and 2 #8 for the neutral/ground (code allows the neutral/ground to be 1 gauge smaller). It'll also need to be installed in underground or outdoor rated conduit.

  • Chris, why is the neutral allowed to be one gauge smaller than the hot since it is carrying the same current? One can see why the ground could reasonably be one gauge smaller, but the neutral?! – Jim Stewart Apr 22 '17 at 10:51
  • In the US under the NEC, the outdoor portion of wiring to a hot tub CANNOT be UF cable. The ground must be an insulated conductor, so THWN in conduit, or special direct burial MC cable, are mandatory. Also, while the code does allow for smaller neutrals in many cases, there is NO "one size smaller" rule. – Speedy Petey Apr 22 '17 at 11:45
  • In a 240v system, the neutral doesn't carry any current under normal operating conditions. – Chris Thompson Apr 24 '17 at 18:04
  • In a straight 240V system a neutral is not required, regardless of the "operating conditions". – Speedy Petey Apr 26 '17 at 11:48
  • Given the cost of conductors of that size and the 100' length, I'd omit the neutral entirely if it's not needed, just have the two hots and a ground. – Billy C. Sep 25 '17 at 19:06

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