Mr. Steam MS90R2401X MS 5 kW Steam Shower Generator of 240 Volt & 1-Phase with Express SteamMr. Steam MS90R2401X 5 kW Steam Shower Generator with Express Steam (240V, 1 Phase) The MS90R2401X is Mr. Steam's 5 kW residential generator built for steam enclosures up to approximately 135 cubic feet think a standard 34 or 35 tiled shower with an 8 foot ceiling. The "X" in the model number means this is the Express Steam version, which cuts heat up time roughly in half compared to the standard MS90R2401, getting steam into your enclosure in about