Rooftop Unit (RTU) Maintenance Checklist for Small Houston Businesses

Published October 16, 2026 · Reviewed October 16, 2026

Part of our Light Commercial HVAC Maintenance & Tune-Up guides.

What is a rooftop unit (RTU)?

A rooftop unit (RTU) is a packaged HVAC system that holds the compressor, both coils, the blower and the controls in one weatherproof cabinet set on the roof, with supply and return ducts dropping through a roof curb into the space below. Strip-center storefronts, small offices, restaurants and clinics across Greater Houston commonly use them because they keep equipment off the sales floor and out of closets.

Many RTUs also include a heating section, either gas-fired burners or electric heat strips, and some include an economizer, a set of dampers that can bring in outside air for cooling when conditions allow. Each of those adds items to the maintenance list.

Because an RTU sits out of sight on the roof, it is usually the last thing anyone checks and the first thing to fail in August.

How often should a small business service its rooftop units?

A small business should have each rooftop unit inspected at least before the cooling season and again before the heating season, with filter changes in between on a schedule set by how fast the filters load. ENERGY STAR recommends annual pre-season check-ups, with cooling checked in the spring and heating in the fall.

Houston's climate pushes cooling equipment harder than most. NOAA's 1991–2020 normals for Houston Intercontinental Airport (IAH) show about 111 days a year at or above 90°F and roughly 3,288 cooling degree days against 1,266 heating degree days. Commercial spaces add internal heat from lighting, equipment, cooking and customers, so many RTUs run long hours even in spring and fall.

For businesses that want a formal reference, ANSI/ASHRAE/ACCA Standard 180 is the industry's published standard practice for inspecting and maintaining HVAC systems in commercial buildings. It is a useful model for building a task list; whether any part of it applies to your building is a question for your lease, your landlord or your contractor.

What is on an RTU maintenance checklist?

An RTU maintenance checklist covers filters, airflow, coils, drainage, electrical parts, the refrigerant circuit, the heating section, the economizer and the cabinet itself. All of these tasks are done on the roof by a qualified technician.

Rooftop unit maintenance tasks and why they matter

Area	What the technician checks	Why it matters
Filters	Size, fit, condition; replacement	Loaded filters starve the coil of air and can lead to freezing
Blower and belts	Belt tension and wear, pulley alignment, motor bearings and amperage	A slipping belt quietly cuts airflow to the space
Coils	Condenser and evaporator coil cleanliness and fin damage	Dirty coils raise energy use and compressor strain
Condensate	Drain pan, trap and line cleared; overflow switch tested	A blocked drain can leak through the roof curb into ceiling tiles
Electrical	Connections tightened; voltage and current on motors; contactors and capacitors	Loose or burned connections cause no-cool calls and component damage
Refrigerant circuit	Charge checked by measurement; leak signs	Low charge means a leak, lost capacity and compressor risk
Gas heat section	Gas connections and pressure, burner combustion, heat exchanger, venting	Safety and reliable heat on cold mornings
Economizer	Damper movement, linkage, sensors and controls	A stuck-open damper pulls humid outdoor air into the space
Cabinet and curb	Access panels secured, gaskets, curb seal, debris and standing water around the unit	Loose panels and failed seals let in water and leak conditioned air
Controls	Thermostat schedule, setpoints and safe operation	A wrong schedule can run the unit all night or leave staff opening to a hot space

The coil, electrical, refrigerant, gas and control items mirror the contractor tasks on the ENERGY STAR maintenance checklist; belts, economizers and roof curbs are the parts that make commercial packaged equipment different from a typical home system.

What goes wrong when rooftop units are neglected?

Neglected rooftop units most often fail through airflow loss, drainage problems and electrical wear, and the first sign is frequently inside the building rather than on the roof.

• Ceiling stains or dripping: a clogged condensate drain or a failed curb seal can send water through the roof opening.
• A space that feels sticky: a dirty coil, a slipping belt or an economizer damper stuck open can leave the space cool but humid.
• Frozen coil: loaded filters or a failed blower belt can freeze the evaporator coil, and the unit stops cooling until it thaws.
• Tripped breakers or a dead unit: pitted contactors, weak capacitors and loose connections are common causes of no-cool calls during peak heat.
• Storm damage: wind can loosen access panels and throw debris into coils; a unit that looks fine from the parking lot may not be.

What can a business owner or manager do without going on the roof?

A business owner or manager can do a great deal from the ground: track comfort, watch for water, manage the thermostat and keep good records. Nobody on staff should climb onto the roof or open an RTU; roof access and live electrical parts are jobs for a qualified technician.

• Know who is responsible. Check your lease. It may assign HVAC maintenance and repair to the tenant, the landlord or both, and it may require proof of service.
• Keep a unit log. For each RTU, record the area it serves, the model and serial number from the nameplate, the refrigerant type, filter size and every service date.
• Write down complaints with times. "Back office warm after 3 p.m." is far more useful to a technician than "AC not working."
• Watch the ceiling. Report new stains near supply diffusers or the unit's roof opening right away.
• Keep returns and diffusers clear. Stacked inventory or furniture against a return grille cuts airflow.
• Review thermostat schedules. Make sure occupied and unoccupied times match your actual business hours.

How do you verify a rooftop unit was actually serviced?

You verify RTU service with a written report for each unit, because you usually cannot see the work yourself. A complete report lists the unit by location and serial number and includes the filter size and date changed, belt condition, coil condition with photos, condensate drain status, electrical readings (voltage, amperage, capacitor values), refrigerant readings, and, in heating season, the gas heat section checks. Ask the technician to note anything deferred and why.

Compare reports season to season. Rising compressor amperage, a capacitor drifting from its rating or a belt replaced more often than expected are early signs that a unit is heading toward a larger repair.

How should you prepare rooftop units for hurricane season?

Before hurricane season, have the technician confirm that access panels are fastened, the unit is secure on its curb and the drain is clear, and photograph each unit for your records. After a storm, have the units inspected before assuming they are fine; the hurricane season HVAC checklist covers storm preparation and post-storm safety in more detail. For a broader look at what a cooling tune-up should include, see what happens during an AC tune-up.

Frequently Asked Questions

How often should rooftop HVAC units be serviced?

At a minimum, rooftop units should get a pre-season check before cooling season and another before heating season, with filters changed in between as often as they load up. ENERGY STAR recommends checking cooling in the spring and heating in the fall. Busy spaces like restaurants or dusty locations may need more frequent filter changes.

Who is responsible for RTU maintenance in a leased space?

It depends on your lease. Some leases assign HVAC maintenance and repair to the tenant, some to the landlord, and some split it, and many require proof of regular service. Read the HVAC and maintenance sections of your lease before you schedule work.

Can my staff change the filters on our rooftop unit?

RTU filters are inside the unit on the roof, so changing them means roof access and opening the cabinet. That work is best left to a qualified technician. Staff can help by keeping return grilles clear and reporting comfort problems and ceiling stains promptly.

Why is my store cool but humid?

A space that feels cool but clammy often points to an airflow or moisture-removal problem, such as a dirty coil, a slipping blower belt or an economizer damper stuck open and drawing in humid outdoor air. A technician can check each of these on the roof.

What is ASHRAE/ACCA Standard 180?

ANSI/ASHRAE/ACCA Standard 180 is a published industry standard practice for inspecting and maintaining HVAC systems in commercial buildings. Facility managers can use it as a model for building a maintenance task list; whether it applies to your building depends on your lease and any requirements from your landlord or local authority.

What should an RTU service report include?

A good report identifies each unit by location and serial number and records the filter change, belt condition, coil condition, condensate drain status, electrical and refrigerant readings, and heating checks in season. Comparing reports over time shows which units are trending toward failure.

Sources

1. ENERGY STAR — Maintenance Checklist — pre-season timing and contractor tasks for cooling and gas heating (as of October 16, 2026)
2. NOAA NCEI — U.S. Climate Normals 1991–2020, Houston Intercontinental (USW00012960) — days at or above 90°F, cooling and heating degree days (as of October 16, 2026)
3. U.S. DOE Better Buildings — ANSI/ASHRAE/ACCA Standard 180 — standard practice for inspection and maintenance of commercial building HVAC systems (as of October 16, 2026)