Existing detached building 3 wire sub panel

[Stevenfyeager]

Customer has an existing barn fed with 3 wires underground 160' I realize we run 4 wires now. If I replace the subpanel (its a mess), am I required to run 4 wires ?
25 years ago or more, ALL of us electricians in this area used to run 3 wire URD to all detached buildings and drive a ground rod. All inspectors passed these.

 

[Buck Parrish]

. I believe there is an exception to existing buildings 250.32. Check with your inspector first to make sure they agree.

 

[petersonra]

The wiring is a old enough that you might want to consider replacing it when you replace the box. When you replace the wiring just replace it with four wires instead of three.

 

[ptonsparky]

Depends.
Is/was this a feeder?
or
Service Entrance?

I agree, ask the AHJ.

25 old is not old for properly installed conductors wires.

 

[petersonra]

Depends.
Is/was this a feeder?
or
Service Entrance?

I agree, ask the AHJ.

25 old is not old for properly installed conductors wires.

But it is old enough it might be worth considering. Especially UG wiring.

 

[Little Bill]

The code used to allow the 3-wire between buildings if there were no metallic paths to cause parallel paths for the neutral. If the barn was legal when it was installed, just changing the subpanel wouldn't trigger changing the feed. I would change the panel and not give a thought to replacing the feeder, unless there is a problem with the feeder.