Lennox 33M14 Heat Exchanger 318973 401 Direct OEM Replacement: Seamlessly replaces Direct OEM Replacement: Seamlessly replaces GE 5412 and Mars 9 watt unit bearing motors with a standard 51 frame footprint ) used to simulate different temperature conditions for staged heating or cooling verification The Lennox 33M14 Heat Exchanger is a heavy duty high heat aluminum heat exchanger assembly engineered for reliable thermal transfer in 10 to 20 ton LGB120 and LGB240 series rooftop units The aluminized finish is critical for high heat applications to prevent the rapid oxidation and scaling that typically occurs at the high temperatures required for commercial heating loads