By Hood Service Company · Corsicana, TX · Updated
The short version
- A rooftop unit is a packaged system, so one cabinet holds everything that cools, heats and moves the air.
- Many businesses schedule full service before cooling season and before heating season, with filter changes in between.
- Dirty coils, worn belts and clogged drains are common causes of avoidable rooftop problems.
- Roof access and all work inside the cabinet belong to a qualified technician.
What is a rooftop unit?
A rooftop unit, often called an RTU, is a packaged system that houses the compressor, coils, blower and often a gas heat section in one weatherproof cabinet, connected to the building's ducts through a roof curb.
RTUs are common on retail stores, offices, restaurants, churches and light industrial buildings because they keep equipment off the floor and serve large open areas. Cooling capacity is measured in tons, and many buildings use several units, each serving its own zone. Because the equipment sits in direct sun and weather year-round, it wears differently than equipment tucked inside a mechanical room.
What does rooftop unit maintenance include?
A thorough visit covers airflow, coils, drainage, the refrigeration circuit, electrical components, controls and the heat section. The exact checklist depends on the unit's age and type and how hard it works.
- Filters: replaced on a schedule matched to the building's dust and occupancy.
- Coils: outdoor and indoor coils inspected and cleaned so they can move heat efficiently.
- Belts and motors: belts checked for wear and tension on belt-drive units, and motors and bearings inspected.
- Condensate drain: pan and line cleared so water doesn't back up into the cabinet or leak into the building.
- Refrigeration and electrical: operating pressures, temperatures, contactors and connections checked by the technician.
- Economizer and controls: on units with an economizer, which brings in outside air when it's cool and dry enough to help cool the space, dampers and sensors are verified along with thermostat schedules.
- Heat section: on gas units, burners, ignition, venting and the heat exchanger inspected before heating season.
How often should rooftop units be serviced?
Many businesses schedule full service at least twice a year, before cooling season and before heating season, with filter changes in between. Restaurants and dusty or high-traffic buildings often need more frequent attention.
In North-Central Texas, cooling does most of the work. Long, hot summers can keep an RTU running for extended stretches, so a spring visit that cleans coils and checks the refrigeration circuit is especially valuable. A fall visit focuses on the heat section ahead of the occasional hard freeze. Kitchen exhaust grease, construction dust and nearby gravel lots can all foul coils faster.
A simple log of service dates, filter changes and repairs for each unit helps you spot patterns and plan ahead for replacements.
What warning signs mean a rooftop unit needs attention?
Watch for areas that won't hold temperature, warm air from vents in cooling mode, water stains on ceiling tiles, new noises from the roof, rising energy bills, and a unit that runs constantly or cycles rapidly.
Our HVAC troubleshooter can help you describe symptoms before you call. Many cooling symptoms mirror the ones homeowners see; see why an AC stops cooling.
- Ceiling stains or drips below a unit, which can point to a clogged drain or a leak at the curb.
- Squealing or slapping sounds, often from a worn or loose belt.
- Zones that drift out of comfort while other units keep up.
- A breaker for the same unit that trips repeatedly.
- Burning or gas smells. For a gas smell, get everyone out of the building first, then call the gas utility or 911 from outside.
What can your staff safely do between service visits?
Staff can keep thermostat schedules accurate, keep supply and return grilles clear, report noises, smells and leaks promptly, and note which areas are uncomfortable. Roof access and anything inside the cabinet belong to a technician.
Roofs carry fall hazards, and RTU cabinets contain high-voltage components, spinning fans and, on gas units, burners. If a unit stops, it's fine to confirm its thermostat is set correctly and check whether its breaker in the building's panel has tripped. If a breaker trips again, leave it off and call for service.
Hood provides commercial HVAC service and light industrial HVAC for businesses across North-Central Texas. Call (903) 602-5108 or contact us.
When should you call a technician?
- A unit blows warm air in cooling mode or won't heat.
- Water is leaking through the ceiling below a rooftop unit.
- You hear grinding, squealing or banging from the roof.
- A breaker for the unit trips more than once.
- Anyone smells burning near the unit or at a supply vent.
Frequently asked questions
Does a newer rooftop unit still need maintenance?
Yes. New units still collect dirt on their coils and filters, and drains still clog. Regular service also documents the unit's condition, which can matter for a manufacturer warranty, so review your warranty terms to see what maintenance it expects.
Why does one rooftop unit run constantly while others cycle?
It may serve a zone with more heat load, such as a sunny storefront or a kitchen. It could also have a problem such as dirty coils, low airflow or a refrigerant issue. A technician can measure its performance and tell the difference.
When does replacing a rooftop unit make more sense than repairing it?
Replacement deserves a look when repairs are frequent, a major component such as the compressor or heat exchanger fails on an older unit, or the unit can no longer keep the space comfortable. Our guide on whether to repair or replace walks through the factors, and the same thinking applies to commercial equipment.
Does Hood work on commercial refrigeration too?
Yes. Hood also services commercial refrigeration. See commercial refrigeration maintenance for what that kind of maintenance typically covers.