90A shop subpanel from main 200A panel

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The Widget

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General Contractor
Afternoon, I have a shop that currently has a 30amp subpanel from the house 200A panel. I plan to upgrade to a 90A main breaker subpanel in the shop, with a 90A breaker in the main house panel. Part of the run will be SER in the house, then transition to URD underground direct bury to the shop, then transition again to SER at the shop. The run will be about 200 feet, likely less.

Is 2/2/2/4 SER AL cable on the interior areas and 2/2/2/4 URD underground adequate?

Thanks for the help!
 
Sounds good.

Is your occupation that of an electrical contractor or general contractor? And please update that on your info. Thanks
 
When #2 is used as a building service it is good for 100 amps. If it is used as a feeder off the main panel 90 amps is the correct size. If you use #2 SER you are fine in the house but you would want the 90 amp breaker in the main panel not the shop. You can have a 90 or even a 100 amp panel in the shop because the wire is and has to be protected at the source. When you switch to URD again #2 is fine but it is usually only 3 conductors, you need to run a copper ground wire underground you can't use aluminum. #8 stranded copper will do the trick. At the subpanel you have to isolate the neutral from the ground, and not use the bonding jumper that comes with the panel, otherwise if you had a bad neutral to the house you would never know the ground would be carrying your neutral current and it isn't insolated or sized as a neutral.

You could use a 100 amp panel with a main breaker in which case it will act as a disconnect which you need to have in an out building. Lable it as a building disconnect. You also need a ground rod, just one at the out building. I assume you are running the underground in conduit, if its worth digging the hole is worth putting in a pipe. 18" under cover so a 2" pipe needs a 20" trench. 1.5 to 2" PVC would do the trick.

I am a Licensed Master out of Boston, semi retired I have to figure out how to make that show up. Anyway that's my thoughts.
 
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