How many 2/0 AWG THW aluminum compact conductors are permitted in a 2 1/2 inch PVC conduit schedule 80?

To determine how many 2/0 AWG THW aluminum compact conductors fit in a 2 1/2 inch PVC conduit (schedule 80), one must consider the conduit fill calculations as per the National Electrical Code (NEC).

For aluminum conductors, the NEC specifies the maximum number of conductors allowed based on each conductor's physical size and the conduit size. The fill calculations take into account not only the diameter of the conductors but also the diameter of the conduit itself to ensure proper spacing and to prevent overheating.

A standard 2/0 AWG aluminum conductor has a specific circular mil area, and there are fill tables in the NEC that outline how many conductors can be accommodated in a given conduit size without exceeding the fill percentage limits. For a 2 1/2 inch schedule 80 PVC conduit, the fill is calculated based on the cumulative area of the conductors, and it can be shown that 7 conductors fit within this conduit size while adhering to the NEC fill requirements.

Thus, knowing these code requirements and calculations leads to the determination that the correct answer is that 7 conductors are permitted in a 2 1/2 inch PVC conduit schedule 80.