The Evergreen boiler extends comfort levels to every area of your property for the long run. The Evergreen is perfect for light commercial or large residential applications and single or multi-unit installations with ZoneStacking up to 24 programmable zones. Its everything you want in heating: quiet operation, aesthetically pleasing design, floor standing or wall mount options, environmental sustainability with Low NOx, heating comfort with lower utility bills and more. This system features a stainless steel fire tube heat exchanger with non-metallic base. Modulating condensing boiler with 10:1 turndown boasts of 95% AFUE (220/299); 96.5% Combustion Efficiency (399). 4 pump/auxiliary outputs and up to 8 multiple boiler control with lead/lag rotation and configurable Auxiliary Input/Output System. The boiler circulator and propane conversion orifice for liquid propane applications is included.