I am wanting to install a 50 amp double breaker and wire a 240 volt outlet using 6/3 with ground. The subpanel is on a detached shop and has a ground bar into the ground. From the main panel to this sub is only 2 hots and neutral. the neutral goes to the only bus in the box which is bonded to the panel and is grounded with a ground round. do i need to run a new wire for a ground from the main panel and make the existing bus the neutral and unbond it or can i put a new bus in, bond it to the panel, and move the ground from the ground rod to the new bus so the neutral is isolated nd be good?
Firstly, before you get BOMBARDED with negative feedback on your post I should offer the best advice I can give you. Visit www.mikeholt.com or other forum (even mine at www.masterthenec.com) and post that question.
However, I will answer your question to assist.
When you install your cable to the detached structure you will need to make sure it contains (4) conductors. (2) Ungrounded (hot), (1) Grounded(neutral) and (1) Equipment Grounding Conductor.
In your remote distribution panel (you refer to as Sub-Panel) you need to ensure that the (1) Grounded(neutral) is terminated on a bus that is isolated from the metal enclosure, this is where all your grounded, yes neutrals in your case are terminated.
The 4th Equipment Grounding Conductor is terminated on it’s own bus that is directly connected to the metal enclosure of the distribution panel. The GEC (Grounding Electrode Conductor) that is needed for that separate structure is installed from the electrode(s) to the EGC bus in the distribution panel per 250.32(B). Again do not connected the Grounded (neutral) bus to the Equipment Grounding Conductor (EGC) bus at the remote structure.
My ultimate suggestion is to review Sections 250.50, 250.52, 250.32(B) among others as well and understand what you are doing. Anything beyond those basic concepts I would say visit one of the boards I explained earlier and you can get additional information. However, the MikeHolt forum is not a DIY forum so that might not be your best choice if you don’t want to get flamed.
Listen to Paul !
Listen to Paul … Then call an electrician AND don’t try to be a do it yourselfer
Or…Ignore Me as i am a hack…ask anyone on Mike Holts site…and still call a Licensed Electrical Contractor…many options to choose from…
If the panel in the detached structure was installed under the 2005 or earlier NEC version it may have been permitted to run a 3-wire feeder and bond the neutral in the sub-panel if certain conditions were met. This is no longer permitted.
Do not do what you’ve suggested:* "put a new bus in, bond it to the panel, and move the ground from the ground rod to the new bus so the neutral is isolated nd be good? ".
*As others have stated hiring an electrician may be the best option.