Rinnai’s Ultra Series condensing water-heating technology combines traditional tankless water heaters with commercial applications. The design incorporates two heat exchangers to achieve optimum water-heating value from every cubic foot of natural gas or propane. The down-fired ceramic burner allows condensation to drain from the bottom of the heat exchanger, protecting the primary heat exchanger and burner. The design maximizes heating value and earns an Energy Factor rating of up to .95. Additional features include: Circ-Logic recirculation; temperature lock; and a scale-detection system.