Rooftop Units (RTUs) in Lexington, KY
The rooftop packaged unit is the dominant HVAC technology for light commercial buildings in this market — restaurants, retail stores, small offices, professional services, and most of the freestanding commercial buildings dotting Lexington’s commercial corridors. The reasons are practical: one cabinet on the roof contains the compressor, condenser, evaporator, blower, and (typically) gas heating section; the cabinet connects to interior ductwork through roof penetrations; the entire system is serviceable from outside without disrupting interior operations. The tradeoffs are also real: outdoor weather exposure accelerates wear, rooftop access requires crane work for major service, and the integration with the building structure adds complexity to installation projects. Lexington Heating and Air installs, replaces, and services rooftop packaged units across Fayette County for the commercial buildings where this technology fits.
What an RTU Actually Is
A rooftop unit is a self-contained packaged HVAC system housed in a single weatherproof cabinet, mounted on a roof curb (a structural frame that supports the unit and provides the duct connection between rooftop and interior). Inside the cabinet:
- Compressor and refrigerant circuit — the cooling system, similar in principle to a residential AC condenser but typically larger capacity, often with multiple compressors for staged operation.
- Condenser coil and fans — outdoor heat rejection, with one or more fans drawing air across the coil.
- Evaporator coil — indoor heat absorption, the cooling and dehumidification surface.
- Blower assembly — typically belt-driven on smaller units, direct-drive on larger or higher-end equipment, moving air through the building’s ductwork.
- Gas heating section — on gas/electric RTUs, the burners, heat exchanger, and venting that provide heating. Heat pump RTUs use the refrigerant circuit in reverse for heating instead.
- Economizer — outdoor air damper and control system that uses cool outdoor air for “free cooling” when conditions allow.
- Controls — thermostat connections, safety devices, staging logic, and often integration with building management systems.
- Filter section — typically holding 2-inch or 4-inch commercial pleated filters.
The RTU cabinet sits on the roof curb, which provides the structural support and the duct opening between the unit and the interior ductwork. Curbs are unit-specific in their dimensions and connection points.
RTU Capacities and Configurations
- Light commercial: 3–6 tons. Small retail stores, offices, restaurants — the most common residential-adjacent size class.
- Medium commercial: 7–15 tons. Larger retail spaces, multi-zone offices, medium restaurants, medical offices.
- Larger commercial: 16–25+ tons. Larger commercial buildings often have multiple RTUs at this scale rather than one larger unit.
- Single-zone: The basic RTU configuration with one thermostat controlling the unit.
- Multi-zone RTUs: Some larger units include integrated zone dampers and controls for multi-zone operation from a single rooftop unit.
- Gas/electric: Gas heating + electric cooling. Most common configuration.
- Heat pump: Refrigerant-cycle heating and cooling with electric resistance backup heat. Increasingly common as building energy codes tighten and electrification incentives grow.
Common RTU Brands We Service
The commercial RTU market is concentrated among major manufacturers; we install and service equipment across the range:
- Carrier (also includes Bryant commercial)
- Trane
- Lennox
- York / Johnson Controls
- Daikin (also includes Goodman commercial and Amana commercial)
- Rheem / Ruud commercial
- AAON
- Mitsubishi commercial (less common in pure RTU configurations; more common in VRF applications)
The brand matters less than the installation quality and the maintenance discipline. A premium unit installed badly underperforms a budget unit installed correctly.
Common RTU Service Needs
Belt and Bearing Service
Belt-driven blowers on commercial RTUs require periodic belt tension adjustment, belt replacement (typically every 2–3 years on high-runtime applications), pulley alignment, and bearing lubrication. The single most common preventive item on commercial RTUs that distinguishes commercial maintenance from residential.
Coil Cleaning
Outdoor condenser coils accumulate dust, pollen, cottonwood, grass clippings, and other debris that drops cooling efficiency dramatically when neglected. Restaurant rooftops face an additional challenge — kitchen exhaust grease accumulation on adjacent surfaces and equipment. Regular cleaning matters more on rooftops than on ground-level residential equipment.
Economizer Service
Economizers fail in ways that are easy to miss without inspection — dampers stuck partway open or closed, sensors out of calibration, control logic drifted from optimal. A failing economizer can either run mechanical cooling when free cooling would suffice (wasting energy) or fail to deliver required ventilation. Quarterly testing is appropriate.
Gas Heat Section Service
Combustion analysis on each heating stage, manifold pressure verification, heat exchanger inspection, flue and vent integrity, gas leak testing. Same fundamental work as residential furnace tune-ups but on commercial-scale equipment with multi-stage operation.
Compressor and Refrigerant Service
Compressor amperage measurement, refrigerant pressures and superheat/subcooling verification, leak detection per EPA requirements where applicable, capacitor testing on PSC motors, contactor inspection. Compressor problems on commercial RTUs are the largest-ticket repairs; catching the conditions that lead to them is part of regular maintenance.
Curb and Cabinet Inspection
The roof curb supports the unit and creates the airtight seal between the rooftop and interior ductwork. Failed curb gaskets allow rainwater infiltration into the interior; deteriorated curb structure can create more serious problems. Annual inspection is appropriate.
RTU Replacement Considerations
- Crane work. RTUs in the 5+ ton range typically require crane mobilization for set or removal. Scheduling involves coordinating with the crane company, building access, and street/parking lot permits if applicable.
- Roof curb compatibility. Existing roof curbs may or may not fit new equipment. Curb adapters can sometimes bridge differences; otherwise, curb modification or replacement is part of the scope.
- Refrigerant transition. Older R-22 RTUs (still in service in some buildings) and aging R-410A equipment face the industry-wide transition toward R-454B. Replacement timing intersects with refrigerant availability and repair economics.
- Electrical and gas service. New equipment may have different electrical or gas service requirements than the old unit. Service modifications are often part of the replacement scope.
- Controls and BMS integration. Modern RTUs include more sophisticated controls than legacy equipment; integration with existing building management systems sometimes requires controls work beyond the unit itself.
- Operational continuity. Many commercial buildings can’t simply shut down HVAC for the duration of replacement. Scheduling around business operations — sometimes including overnight work — is often required.
- Tax considerations. Section 179 expensing and bonus depreciation may apply to commercial HVAC replacement, potentially making the math more attractive than gross cost suggests. Consult your tax professional for specifics.
Frequently Asked Questions
- How long do rooftop units last?
- With proper installation and regular maintenance, typically 15 to 20 years for commercial RTUs, sometimes longer on lower-runtime applications. Higher-runtime equipment (24-hour operations, intensive commercial use) lives shorter; well-maintained equipment on moderate-runtime applications can exceed 20 years. Rooftop weather exposure is harder on equipment than ground-level installation; this affects the lower end of the range.
- What does RTU maintenance involve?
- Quarterly preventive service is the typical baseline: belt and bearing inspection, condenser and evaporator coil cleaning, refrigerant verification, combustion analysis on gas heat, economizer testing, electrical inspection, filter replacement, condensate drainage service, and controls verification. High-runtime applications add monthly inspection cycles focused on filter changes and quick issue identification.
- Do you handle the crane work for RTU replacement?
- Yes, we coordinate crane scheduling as part of RTU replacement projects. Crane mobilization requires lead time and is typically scheduled for daytime hours when wind conditions allow. Building access, street or parking lot permits if applicable, and coordination with building tenants for any work near the rooftop unit are all part of the project planning.
- Can you service all RTU brands?
- Yes. We service rooftop units across the major commercial manufacturers (Carrier, Trane, Lennox, York, Daikin, Rheem, AAON, and others). Our technicians work with the equipment’s manufacturer documentation for specific service procedures, and we maintain stock of common parts across brands. Some manufacturer-specific parts require special order; we communicate timing upfront.
- Does new commercial HVAC qualify for tax benefits?
- Section 179 expensing and bonus depreciation may apply to qualifying commercial HVAC replacements installed in qualified business properties. The specific rules, limits, and qualification criteria change with tax legislation and depend on your business situation. Confirm specific eligibility and tax treatment with your accountant or tax professional rather than relying on contractor advice.
Schedule RTU Service for Your Lexington Commercial Building
From a single rooftop unit needing service to a multi-RTU replacement project with crane coordination, our commercial team delivers on the timelines that commercial work requires. Across Lexington and Fayette County.
- Phone: (859) 215-5241
- Address: 343 Cassidy Ave, Lexington, KY 40502
- Email: [add business email before publishing]