HydroTherm has introduced the FX Series of high-efficiency gas-fired, cast-iron residential boilers. The new line is up to 86% efficient. All FX Series direct-vent boilers use 100% outside air for combustion to reduce heating costs and provide safe and dependable operation. With a footprint of 29 inches, the line is designed to fit the floor plan of any home. Sizes range from 70 to 210 MBH, the widest size range of any direct-vent, residential boiler on the market.