Due to construction we are putting in a temp guard shack. It is about 4x8 with a window AC, a light and a few plugs for battery chargers. It is made of steel, with windows on 3 sides. It is going to be powered by a small portable generator. There will be one 20 amp circuit for the whole shack.

Question one is do we need to drive a ground rod for this shack powering it from a portable generator?

Question two is the same, except what if we powered it with a single circuit from the nearest building?

As for the term "temp", construction is scheduled to take place for 18 months. The shack will be removed after the construction and put someplace else.

Many thanks for any help.