If your business runs on a commercial rooftop unit (RTU), late summer is the single best window of the year to catch small problems before they turn into a five-figure emergency. Here in the Puget Sound area – Mukilteo, Lynnwood, Seattle, and everywhere in between – our RTUs work overtime through a mild-but-humid summer, then get asked to flip almost immediately into heating mode as the rain and cold settle back in by October.
Most commercial rooftop unit failures we get called out for aren’t sudden. They’re the result of a small issue – a clogged filter, a refrigerant leak, a worn belt – that had all summer to get worse and finally gave out the first cold week of fall. A 30-minute inspection now can save a restaurant, retail store, or office building from a no-heat call (or a full system replacement) in November.
Here’s the exact checklist our technicians run through on commercial rooftop units across King and Snohomish County.
Why End-of-Summer Timing Matters in the Puget Sound Climate
Unlike drier climates, our region’s RTUs deal with near-constant moisture, salt air near the water, and heavy debris load from fall leaf drop landing directly on rooftop coils. Add in the operational switch from cooling to heating mode, and early fall is when latent summer wear actually shows up as a breakdown. Businesses that get ahead of it with an inspection in August or September routinely avoid the “no heat, full building, Monday morning” emergency call that costs more and takes longer to fix under pressure.
The 12-Point End-of-Summer RTU Checklist
1. Air filters Check and replace if needed. A dirty filter after a full cooling season is the #1 cause of reduced airflow, iced coils, and higher energy bills heading into fall.
2. Condenser and evaporator coils Inspect for dirt, debris, pollen, and – especially near Puget Sound waterfronts – corrosion. Dirty coils force the unit to work harder and shorten compressor life.
3. Refrigerant levels and leak check Low refrigerant strains the compressor and is often the first sign of a slow leak that will fail completely once heating demand kicks in.
4. Belts and bearings Summer runtime wears belts down. A cracked or loose belt is a cheap fix in September and an emergency no-cool/no-heat call in October.
5. Electrical connections and contactors Vibration and heat cycling loosen electrical connections over a season of heavy use. Loose or corroded contacts are a leading cause of unexpected shutdowns.
6. Condensate drain lines and pans Algae and debris buildup from summer humidity clogs drains, leading to water damage on the roof deck or ceiling below if not cleared before the wetter fall season.
7. Heat exchanger inspection Before switching over to heating mode, the heat exchanger needs to be checked for cracks or corrosion – a safety issue as much as a performance one.
8. Thermostat and control calibration Confirm the changeover from cooling to heating mode is accurate. Miscalibrated controls waste energy and lead to uncomfortable, inconsistent building temperatures.
9. Ductwork and airflow check Verify even airflow across the building. Uneven heating/cooling is often traced back to duct leaks or blocked returns that got progressively worse over summer.
10. Roof curb and unit mounting Puget Sound rain means roof penetrations and unit curbs need a visual check for seals, rust, and water intrusion points before the fall storms arrive.
11. Economizer and outdoor air dampers These moving parts stick or corrode with seasonal humidity. A stuck damper hurts efficiency and indoor air quality year-round.
12. Overall performance test and log review A full cycle test comparing current performance against manufacturer specs and past service records – the difference between guessing your unit is fine and knowing it is.
What Happens If You Skip This
Commercial RTUs that go without a seasonal inspection are far more likely to fail exactly when a business can least afford it – during the first cold snap, during a weekend rush, or in the middle of a heating changeover. For restaurants, retail stores, and offices across Seattle, Lynnwood, and Mukilteo, a rooftop unit failure isn’t just a repair bill – it’s lost revenue, unhappy customers, and in some cases a forced temporary closure.
Get Ahead of Fall – Schedule Your Commercial RTU Inspection Today
Lynnwood Heating LLC has been keeping commercial rooftop units running across the Puget Sound area – including Seattle, Everett, Bellevue, Redmond, Kirkland, Lynnwood, Mill Creek, Bothell, and Mukilteo – for over 35 years of combined team experience. We’re licensed, bonded (license #LYNNWHL825D9), and rated 4.8 stars by the local businesses we serve.
Whether you manage a single storefront or a portfolio of commercial properties, a fall-ready inspection now means one less thing to worry about when the temperature drops.
