Sub-panel from ATS

Basta Brown

Our main panel is located in the kitchen. There are several factors which prevent locating a sub-panel next to or near main. The closest service line from the main panel is through the ATS located in a detached enclosed storage area. The power supply to the ATS is fed via a 3 in. aluminum conduit. Power is carried through #4 wire.
I wish to mount a Seimens panel (12 space) to service a "dirty workshop" and plan to run 3 THNN and bare copper #6 lines to the ATS. Can I connect or tap the service line from the main connected to the ATS to supply the sub-panel? The panel will supply power to lighting and convenience outlets. It will also include a 220 (50amp) outlet for a welder. Lights and outlets will be served by separate 25 amp breakers.

J. V.

You can extend a service as long as it never enters the structure. You can set a sub panel if you can protect the feeder and the sub with a OCPD (breaker or fuses). In this case I say no, you cannot do this. I will need to check further and someone else might have a concrete NEC based answer. But my answer at this moment is NO.