The plan is to bring buried conduits horizontally into the side of a vault.
The sealing fittings would be installed on the conduit stubs at the inside of the vault wall. No wires or sealing compound would be installed yet.
Holes would be cut into the back of a NEMA 12 box. The box would then be mounted to the wall with the conduit and open sealing fittings entering the box through the back of the box.
Many conduits inside the vault from equipment would be installed on the walls and enter the box from the sides/top/bottom.
Wiring would then be installed and the compound poured into the sealing fittings.
This method provides a simple way of transitioning from the conduit system inside the vault to the buried ductbank. I think the appearance would be clean and hide the sealed conduit stubs, which otherwise would stick out of the wall about 12-15 inches once the sealing fittings and pulling elbows were installed.
NEC 501.10(b)(4) allows gasketed general purpose enclosures for wiring where no arcing devices are installed.
