Conduit Runs and box wireing

[Giles]

I am adding a branch circuit box to a storage room. This box will supply power for a 220v welder and a small 220 4K watt heater. I have noticed that all the 110v wireing is in 1/2" conduit from the celing down.
Is this required by most codes, and what about "overhead runs"?
Also, since this box will be mounted in a joining separate room with main breaker panel, what are the grounding rules--since there is no main breaker and no way to bond the ground on the new box?

[cacher_chick]

Wiring must be in conduit where in places where it must be protected from physical harm. Some local codes require conduit throughout.

I don't understand your question regarding grounding.
All metal electrical boxes and receptacles must be grounded, be it through conduit and/or a separate ground wire.

[Giles]

The box I am installing does not have a main disconnect. It is a QO square D, 6 space #QO6-12L100S. It is my understanding that a sub panel must be bonded and I know how this is done. However there is no way to disconnect the grounds and neutrals as there is only one ground bar. There is a bonding screw.
I plan to run supply wires from the main panel just as I would if I were adding a 220v recepticle.
Is this correct?
I am not new to electrical work but I am not an electrician. I go to the extremes sometimes to make sure it is done correct, and I think that is good.
THANKS for helping.

[drick]

You need a separate ground bar. You can purchase these separately. Just screw one into the back box. There are usually unused screw holes in the back of the box for this purpose and the bar usually includes the screws. The existing bar should be isolated from the box. This is your neutral bar. Just remove the grounding screw from it. Unlike in your main panel neutrals and grounds must be kept separate in a sub panel.

-rick

[LLigetfa]

In our regulatory domain, I don't believe that metal conduit is adequate for grounding and that a ground wire is required.

[jwelectric]

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing
the circuit conductors shall be one or more or a combination
of the following:
FPN: For effective ground-fault current path, see 250.2
Definition.
(1) A copper, aluminum, or copper-clad aluminum conductor.
This conductor shall be solid or stranded; insulated,
covered, or bare; and in the form of a wire or
a busbar of any shape.
(2) Rigid metal conduit.
(3) Intermediate metal conduit.
(4) Electrical metallic tubing.