A fuel cell system includes at least one modular enclosure having a top wall, a bottom wall, and a plurality of side walls that connect the top wall and the bottom wall and close off the modular enclosure on all sides; at least one fuel cell stack disposed within the at least one modular enclosure; at least one piping manifold configured to supply at least one process gas to the at least one fuel cell stack and to receive at least one exhaust process gas from the at least one fuel cell stack; and at least one process gas seal configured to seal the at least one piping manifold. The at least one process gas seal is effected via a static force from a weight of the at least one fuel cell stack or a weight of the at least one piping manifold.