An electrical equipment cabinet cooling device includes an electrical equipment cabinet having a cabinet outer frame defining an inner perimeter wall. A planar outer cabinet wall is positioned within the inner perimeter wall. A two-phase thermal device includes spaced and opposed first and second transfer walls. An outer perimeter wall connects the first and second transfer walls and defines an interior sealed cavity between the first and second transfer walls. The outer perimeter wall is sized for slidable receipt within the inner perimeter wall. A liquid/vapor retained in the interior sealed cavity acts as a heat transfer medium between the first and second transfer walls. A convective cooling block has a planar end face in direct contact with the second transfer wall. Heat transfers to atmosphere in a path including the outer cabinet wall, the first transfer wall, the liquid/vapor, the second transfer wall, and the cooling block.