Hi Guys,
The table at the web site is not very useful to most folks in the U.S. It is given in funny units, wherein a comma that appears to be for the thousands column is really a decimal divider to us. Also, it is given in millimeters and the square millimeter for area. And, this table provides only one of many overall diameters of the cable, including insulation (which can and does vary in thickness).
Try Table 8, Conductor Properties, in the National Electrical Code (NEC). The actual sizes (diameter) in regular units of the 7-stranded conductors are:
AWG 8 0.049 inch (1.23 mm)
AWG 6 0.061 inch (1.56 mm)
Brewman, the sizes and breaker ratings that you mentioned would be correct, if you used 60 degrees C (140F) wire. But, you shouldn't. THHN wire or equivalent 75 degree wire is usually required, in order to meet the UL standard and to be in compliance with the NEC. There are 3 regular wire ratings - 60, 75 and 90 C. The one that should be used for spas is 75C (167F). Here are the ampacities as listed in Table 310.16, Allowable Ampacities of Insulated Conductors ... for copper conductors:
60degree 75degree 90degree
AWG 8 40 amp 50 amp 55 amp
AWG 6 55 amp 65 amp 75 amp
Additionally, manufacturers may specify somewhat different sizes, as specifically approved by the testing agency (UL, ETL, etc.). And, they may require that the connection to the spa be done in a different standard size, e.g. #6. Usually, the electrician may select an appropriate size conductor up to the spa, but may need to connect to and use a short piece of another size wire to connect to the spa. There are many reasons for other size wire. One example is when there is a need to use a larger size, because a long wire run in the typical size would cause more than a 3% voltage drop. This is not acceptable and a larger size wire is required.
Electro
