Sterling HVAC’s Xcelon system is a rooftop make-up air unit that combines hydronic condensing boiler technology with advanced air distribution and heat recovery methods for levels of efficiency up to 98%. Its engineering integrates hydronic technology, a new air distribution system and an integrated control platform to produce ultra-high efficiencies. Available with an 800- to 1,200-mbh heating capacity, it utilizes a factory-charged, closed-loop 35% glycol mix for freeze protection with no separate water supply required.