Rooftop Unit / RTU

How a packaged rooftop unit works

Where a typical home splits its system between an outdoor condenser and an indoor furnace or air handler, an RTU packages everything in one cabinet: compressor, condenser and evaporator coils, blower, controls, and usually a gas heating section or electric heat. The unit sits on a roof curb, with supply and return duct openings passing straight through the roof deck into the space below. Many RTUs include an economizer, a damper assembly that pulls in outside air for free cooling when the weather allows, and larger buildings often run several units, each conditioning its own area of the floor plan.

What building owners in the Philadelphia area should watch

An RTU lives outdoors year-round, taking the full brunt of Pennsylvania summers, winters, and everything wind and weather deposit on a roof, so it tends to need more frequent attention than sheltered residential equipment. The maintenance fundamentals are filters changed on schedule, coils kept clean, belts and bearings inspected, economizer dampers verified, and drainage and roof curb seals checked before leaks find the ceiling tiles. Telltale signs of trouble reaching the space below include weak airflow, uneven temperatures between zones, and rising utility bills. Because access requires getting on the roof safely, RTU service is a job for qualified technicians rather than in-house improvisation, and a regular maintenance schedule is the cheapest insurance a flat-roofed building can buy.