We recently purchased a new home that has a 16 x 30 steel building in the back yard approximately 100ft from the main panel. The building has power run to it off a 60 amp breaker in the main panel. The current sub panel is an old fuse box that desperately needs an upgrade. It appears that at some point a previous owner started to upgrade the electrical but never finished. There are three #2 aluminum feeders 2 hot and one neutral but no ground. I am going to replace the sub panel with a new GE panel and want to know the proper way to add a ground. Can I just run #4 wire from the panel to two grounding rods outside of the building or do I need to run a new wire back to the main?
The big reason I'm asking is that if I am going to pull a new wire I'm going to end up redoing the whole feed with a larger wire so that I can run a 125 amp sub panel. The building will eventually become my new shop with power hungry equipment. If I can safely get it up and running now for a minimum of expense that would be great otherwise I will have to plan for the larger project. Thanks for the advice.
Shawn in New Orleans
Best Answer
Since it is an existing installation you don't need the ground wire until you upgrade it.
Your inspector may even allow you to use the 3-wire method with the new panel until you replace the wiring.
Fuse panels are not necessarily obsolete until they are no longer serviceable.
You could use it as-is unless you have the need for more than 60 amps right away. If it is working fine now don't be in a big hurry to spend your money.
Good luck!