Hi James. If this is a residential spa, they are probably assuming that you would be using type NM cable. Are you? If so 334.80 is going to limit you to the 60 degree column (as Bob mentioned).Well what I am trying to figure out for sure is I am wiring up a spa for a friend and was planning on using 3 # 8's and a 10 ground which is good for 50 amps in th 75 deg. column, but the wiring diagram that came with the spa says do not use smaller than # 6 awg can you help me with this, the run is only about 30 feet.
Part of the reason is that NM is often installed in areas where it will be surrounded by thermal insulation that will limit the heat dissipation from the cable. There are some tests that show if you surround the NM with insulation (an example would be blown insulation in an attic or wall cavity) and load the cable to its maximum permitted 60?C ampacity, that the conductor temperature will actually exceed 90?C.I would like to know why romex can only be sized according to the 60deg. chart.
I thought the AHJ can only enforce the minimum NEC requirements. I realize that in this case the manufacturer's requirements trump the NEC, but how could an AHJ insist on more than the NEC minimums?Anyone, from the manufacturer to the designer to the contractor to the owner, and even the local AHJ, can insist on more strict standards than are contained in the NEC.
You are right. I should have put it the way Bennie did:Originally posted by peter d: I thought the AHJ can only enforce the minimum NEC requirements. . . . how could an AHJ insist on more than the NEC minimums?
The jurisdiction can enact laws that require more than the NEC. If they do, then the Inspector, acting as the AHJ, and enforcing the local laws, can thereby enforce requirements beyond those of the NEC.Inspectors can only enforce the laws adopted by the jurisdiction.
Isn't it the manufacturer who knows if the terminals are good for 60 C or 75 C?Inspectors can only enforce the laws adopted by the jurisdiction. Manufacturers instructions are not laws.