The Mighty Therm2, 200 - 400 series boiler and volume water heater is available in 200, 300 and 400 MBH sizes and operates at an environmentally friendly 85% efficiency with low NOx emissions. Laars Heating Systems designed the Mighty Therm 2, 200-400 series, to be easy to use, install and maintain. It utilizes basic cap & bulb temperature controls and features a low voltage terminal strip for straightforward troubleshooting. The compact modular design, top or rear venting options and the ability to be installed either indoors or outdoors, results in installation flexibility.