This appliance is a gas-fired direct vent hot water boiler with cast aluminum boiler sections.• The heating system water absorbs large amounts of heat from the cast aluminum heat exchanger, cooling flue gases and causing condensation.• Sealed combustion, premix gas burner, and low flame temperature means reduced CO and NOx emissions, which contribute to cleaner and healthier environment.• This appliance takes its combustion air directly from outdoors (sealed combustion) and does not compete with building occupants for fresh air.• Sealed combustion (also known as “direct vent”) is safest and best way to obtain plenty of clean combustion air.• Induced draft fan draws in outside combustion air, takes cooler flue gases from boiler unit and provides positive removal of flue gases from the building through readily available PVC and CPVC pipes.• These low pressure gas-fired hot water boilers are design certified by CSA International for use with natural gas and propane gases (90-100 model is certified for natural gas only).• Boilers are constructed and hydrostatically testedfor maximum working pressure of 50 psig (pounds per square inch gage) in accordance with A.S.M.E. (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code Section IV Standards for heating boilers.