Is it necessary to install the Service panel on a board when installing it on the poured walls in the basement. Or can the contractor just "shoot" on the wall with a power actuated pin setter?

Putting it on a board would make it much easier to fasten romex/conduit/whatever near the panel. Especially if its romex... good luck getting romex staples into concrete.

I believe there has to be a 1/4" air space behind a metal cabinet attached directly to concrete that can accumulate moisture.
The wood relieves the installer of that.
If I get a minute I will dig up the specifics.

Greg's answer is correct, however you'll find that most panels have little bump outs where the mounting screws go that just happen to protrude about 1/4 of an inch.

If your panel is like this, you should be able to mount it on concrete. However, if the poured wall isn't all that smooth, or the forms weren't well aligned, you may have concrete touching the back of the panel in places. Usually, this is right where you want a screw to go such as for a grounding bar or the main bonding jumper.

I'd suggest using some washers or short slices of 1/2" PCV conduit to make spacers to get the panel well over 1/4" off the concrete unless its a real smooth wall.

I'm seeing installers shooting the panel on the poured cement walls and not using anchors and screws. I'm sure they don't maintain the .25" standoff that the dimples on the back of the panel provide. Am I getting to picky in my old age?

I guess it all depends on what the chance of moisture accumulating behind the cabinet.

I buy a 4'x8'piece of plywood, & have it cut into 3 pcs @ the Big Blue Box.
Makes a very neat looking installation, & will insure that the panel will not rust.

Who in their right mind would shoot a panel up with pins, especially right to the concrete?
Sound bush league to me.

312.2 requires the 1/4 inch space. If the installer chooses to install the panel directly to the surface (provided it has the 1/4 inch 'dimple', that is acceptable as per code. Going beyond the code is great, but cannot be enforced.

Pierre

Not directly relevant to the NEC I know, but back in the days when British houses had basements or cellars the normal approach was to mount a sheet of plywood to the walls using porcelain standoffs, leaving a gap of about 3/8 to 1/2-inch.

The standoffs were designed in such a way that they went right through the board, effectively providing not only mechanical separation but also electrical insulation between board and fixing screws.