Rooftop Unit Service in St. Louis, MO

Rooftop unit service keeps a self-contained package unit running without taking floor space inside the building. One cabinet on the roof holds the compressor, coils, fans, controls and, on most units, a gas or electric heat section. Kenan Corporation repairs these units for light commercial buildings, including small offices, shops and restaurants, and helps owners decide when upkeep stops paying off.

What is a rooftop unit and why does it fail?

A rooftop unit, or RTU, is a package system that heats and cools a space through ducts from the roof. Because everything is in one weatherproof box, a single failure can stop both heating and cooling.

Roof exposure is the main reason these units wear out. Sun, rain, ice, leaves and cottonwood hit the cabinet and coils without shelter. The belt, blower, contactor and capacitor run for many hours each season. In a small restaurant, grease vapor adds a film to coils and filters, which raises pressure and cuts airflow.

What does rooftop unit service include?

Service means testing the parts that most often fail, then reporting what you need to know in plain language. Typical work on a rooftop unit follows this list.

• Airflow: filters, belts, blower wheel and motor.
• Cooling circuit: condenser and evaporator coils, refrigerant pressures, condensate drain.
• Electrical: capacitors, contactors, relays, wiring and connections.
• Heat section: igniter, flame sensor, gas valve and venting on gas units.
• Controls: thermostat settings, schedules and economizer dampers.

Each item gets a note of what was found, what was done and what to watch. The technician checks what else is working before the visit ends. If the visit turns up wear you did not call about, you hear it as an option, not an upsell, and you decide.

Should you repair or replace a rooftop unit?

Repair when a part failed and the cabinet and compressor are sound, and replace when the next failure is likely to cost more than the unit is worth. Contractors citing ASHRAE service-life tables put a single or multi-zone rooftop air conditioner at about 15 years, so a unit in its late teens deserves a closer look.

Our commercial HVAC repair page covers the repair side. For homes with a similar decision, see AC replacement. We would rather repair your unit than pressure you into a new one.

What does a rooftop replacement involve?

A replacement is a planned project with lifting, electrical, gas and roof work, so it needs more questions than a repair. Put these in the written quote before you sign.

1. Sizing. A load calculation for the space, not a copy of the old tonnage.
2. Curb. Whether the existing curb fits or needs an adapter.
3. Lift. Crane or hoist arrangements and the access path.
4. Roof. Who protects the membrane and who answers for any roof damage.
5. Utilities. Gas piping, electrical disconnect and condensate routing.
6. Permit. Who pulls it, which office, and whether inspection follows. Rules differ by city and county, so check with the local building office.
7. Refrigerant and efficiency. EPA's Technology Transitions rule limits new light commercial air conditioning to refrigerants with a global warming potential under 700. Ask which refrigerant the unit uses and its efficiency rating.

Which permits and licenses cover a rooftop swap?

Plan on a permit even for a like-for-like unit. In the county, Public Works requires one for any system replacement, done by a contractor licensed for mechanical work. Hazelwood lists the 2021 International Mechanical Code as adopted, and the City of St. Louis adopts the 2018 edition. The City's Mechanical Section, at 314-622-3313, can say how commercial replacements are handled.

Missouri has no statewide HVAC license, so ask any contractor, including us, which license your address needs. The installing contractor pulls the permit; have the quote say so.

Our guide to rooftop unit replacement planning walks through budgeting and scheduling in more detail.

What does rooftop unit service cost in St. Louis?

A repair is priced by the fault, and a replacement by the project. The one local figure we cite is Angi's 2026 range of $75 to $150 per hour for HVAC labor in St. Louis, a market range and not our quote. We found no reliable published St. Louis price for rooftop replacement, so we state none.

What moves the number:

• Tonnage, efficiency rating and refrigerant
• Crane or hoist time, and a curb adapter if the old curb does not fit
• Gas, electrical and condensate work
• Roof protection and permit fees
• For repairs, the part and how hard the roof is to reach

Ask for lift, curb and roof items listed separately.

What should owners and managers document?

Documentation protects you at renewal, at a warranty claim and at a property sale. Keep these records for each rooftop unit.

• Model and serial number, plus a photo of the nameplate.
• Install date and, if known, the installing contractor.
• Every service invoice, with what failed and what was replaced.
• Filter and belt sizes, so a quick swap needs no guesswork.
• Roof access instructions and who holds the key.

If the equipment has a manufacturer warranty, the terms belong to that warranty. Read them before authorizing a part, since some require specific parts or documentation.

How is rooftop unit work scheduled in an open business?

Schedule the noisy and disruptive parts for hours when the space is empty. Tell us when staff arrive, when customers come and whether the kitchen runs on a separate system. We are open 24 hours and offer same-day service when the schedule allows, so an urgent failure can be reported any time.

Planned work, such as belts, filters and coil cleaning, can be booked ahead for a quiet morning. A replacement usually takes most of a day, and good planning puts the lift and the electrical hookup in the same window. Ask how the building will be heated or cooled in the meantime.

Why Kenan Corporation for rooftop unit work

Kenan Corporation lists light commercial HVAC among its services, and the proof we can offer is the pattern customers describe on Google, where we hold a 4.6★ rating from 29 reviews as of October 2026.

• Diagnosis before parts. A Google reviewer who was told a new furnace was needed had the problem traced to a capacitor, and it was fixed. We bring the same habit to a package unit.
• Follow-through. Monty M. wrote that the technician knew the issue, replaced the item and checked that everything else worked.
• A clear, upfront quote. The quote comes before work starts, so a landlord or manager can approve it.
• Open 24 hours. Call any time about a failed unit.

We serve Bridgeton, Maryland Heights, Hazelwood and Florissant, among others. For a scheduled plan, see commercial HVAC maintenance.

Where we service rooftop units

• Bridgeton: county Public Works reviews and issues every mechanical permit in the city, so a rooftop replacement permit goes through the county.
• Maryland Heights: Westport Plaza covers more than 700,000 square feet, and city offices cool from packaged rooftop units.
• Hazelwood: buildings near the old Ford plant site keep heating and cooling in packaged rooftop units.
• Florissant: ask a rooftop installer which city paperwork it has filed, since the city lists a bonding and insurance form.
• Clayton: the city issues its own mechanical permits through an online portal and enforces the 2021 International Mechanical Code.
• Creve Coeur: one rooftop unit on a low office building off Olive Boulevard is work we handle.
• St. Charles: the city licenses HVAC contractors through Community Development and asks new applicants for proof of testing.
• St. Peters: Mid Rivers Mall anchors the city, and its code requires contractors to be examined and licensed by St. Charles County first.