When it is referred to 6-pole/8-pole isolator or switch-disconnector, usually what is meant is a set of changeover assembly (2x3P/2x4P). Check the attached image as an example of an 8-pole switch-disconnector (refer to 8 Pole switch-disconnector.png). So upon the rating, you could be directed to the suitable switch-disconnector assembly. For example, for 8P 250A rated isolator, you would be advised to use the attached order form (Compact INS or Compact NSX)
