220V Oulet in a detached garage from a subpanel

[jack.archer]

I have a detached garage that I have added a feeder panel (sub-panel) to for extra power. Code required that it was a four wire connection from the main panel in the house (Two hot, ground, and neutral). Also, per code the two ground rods were required and the neutral bus was to NOT be connected to the grounding bar in the subpanel.

Question: (finally) I would like to add a 220v outlet for a dust collection machine -- easy wiring, only three wires, two hots and a ground -- does the ground go to the grounding bar? This makes me nervous as there is not dedicated neutral connection and the neutral and grounding bars are not bonded -- as they would be in a normal -- in the house set up.

[Lew Hodgett]

[e-mail] wrote: > I have a detached garage that I have added a feeder panel (sub-panel) > to for extra power. Code required that it was a four wire connection > from the main panel in the house (Two hot, ground, and neutral). Also, > per code the two ground rods were required and the neutral bus was to > NOT be connected to the grounding bar in the subpanel.

Good.

You should have a ground bus bar in the sub panel that is insulated so the ground is carried back to the house ground rod.

Lew

>

[gfretwell]

You are doing fine so far. The ground goes to the ground bus, which will be at ground potential as compared to the floor. If you connected to the subpanel neutral the case of your dust collector would be a couple volts above ground due to the voltage drop(rise) from the load.

Your fault path is through the ground, back to the house and then to the neutral.

[alan]

Absolutely attach the ground to the ground bar, which should be attached to the main (panel) ground and to the ground rod at the garage. Do not bond the sub-panel neutral to the ground. That's code and correct, whether for a single or two pole circuit.

[jack.archer]

Great! Thanks for the information. I really want to meet code requirements -- but the code is a little confusing to me (newby).

I d> On 6 Sep 2006 18:50:02 -0700, [e-mail] wrote: >

[Mike Marlow]

Someone correct me if I'm wrong, but doesn't code state one ground form or another, depending on attached or detached structures? Wouldn't a 4th wire and separate ground rods be a code violation - more than one ground point?

[gfretwell]

Nope, the additional rods simply become part of the grounding electrode system. The more the better. What does only happen once is the main bonding jumper where the neutral gets bonded. That is supposed to be in the service disconnect enclosure. There is one exception that allows a 3 wire feeder and a bonded neutral in a separate building but that will be going away in 2008