The Most Common Problems With Light Commercial Packaged ACs (and How to Prevent Them) — Tony’s Real-World Playbook
Commercial HVAC failures don't happen because the equipment is bad. They happen because commercial buildings are tough, unpredictable environments where rooftop units are pushed to their limits for years at a time.
And when a 10-ton light commercial packaged unit starts failing? Your building feels it FAST.
Hot rooms.
Humidity spikes.
Noise complaints.
Breaker trips.
Uneven cooling.
Units cycling nonstop.
Emergency service calls.
I’ve spent years climbing ladders, crawling around ductwork, fighting rooftop sunburn, and fixing the same repeat failures in light commercial packaged units across retail, offices, warehouses, gyms, and restaurants.
The problems are predictable. And preventable.
But only if you know what’s coming.
This is Tony’s full, unfiltered breakdown of the most common issues commercial 10-ton packaged units face — what causes them, what they look like, and how building owners can stop them before they turn into costly repairs.
Let’s get into it.
Why Light Commercial Packaged Units Fail So Often
Rooftop units have a tough life. Unlike residential systems tucked in basements and backyards, commercial packaged units:
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Sit in direct sun
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Face high winds
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Deal with rain, snow, ice, hail, dust, salt, and pollution
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Run for 2,000–4,000 hours per year
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Serve unpredictable loads
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Must meet strict ventilation demands
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Often aren’t maintained enough
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Are installed on roofs that aren’t exactly “gentle”
If your RTU was a person, it would need therapy.
But once you understand the stresses these units face, the common problems start making sense.
Problem #1: Dirty Coils — The #1 Efficiency Killer
Dirty coils are the most common and most damaging issue in commercial HVAC.
A grimy coil can reduce efficiency by 20–40%, cause the compressor to overheat, and push your rooftop unit into early failure.
Why Coils Get Dirty
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Rooftop dust
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Debris from nearby vents
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Pollen
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Exhaust fumes
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Bird droppings
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Pollution in urban areas
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Grease in restaurant districts
Even a thin layer of dirt insulates the coil and blocks heat transfer.
What Dirty Coils Cause
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Higher energy bills
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High head pressure
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Compressor damage
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Reduced cooling capacity
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Longer runtimes
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Frozen coils
Here’s a general reference on coil heat-transfer performance:
[HVAC Coil Fouling Factors]
How Tony Prevents It
Clean coils every 6–12 months.
Period.
Doesn’t matter if you “think” they look clean.
Problem #2: Low Airflow — The Silent Destroyer
If I had a dollar for every airflow problem I’ve fixed, I’d retire.
Low airflow causes:
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Coil freezing
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Weak cooling
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High static pressure
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Compressor stress
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High fan motor amps
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Poor humidity control
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Noise
Common Causes
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Dirty filters
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Undersized ductwork
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Poor curb adapters
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Misaligned transitions
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Blocked returns
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Collapsed flex duct
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Dirty blower wheel
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Closed fire dampers
Here’s a basic airflow concept reference:
[Commercial Airflow and Static Pressure Basics]
Tony’s Fix
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Replace filters regularly
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Check static pressure annually
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Clean blower assemblies
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Inspect duct transitions when replacing the unit
Airflow is everything.
Without it, nothing works.
Problem #3: Refrigerant Issues — Leaks & Charge Problems
Refrigerant issues don’t always start big.
They begin as tiny leaks, often invisible, often ignored, until:
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The system runs nonstop
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Coils freeze
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The compressor overheats
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Head pressure drops
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Capacity tanks
How Leaks Happen
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Vibrations
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Coil corrosion
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Weak solder joints
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Old service valves
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Pitted aluminum
Restaurant and coastal environments see the most leaks.
Here’s a reference about refrigerant leakage patterns,
[Refrigerant Leak Behavior Overview]
Tony’s Rule
Check refrigerant performance once per year.
Not just pressure — performance.
Problem #4: Economizer Failures — The Building Comfort Saboteur
Economizers are designed to save energy by pulling in cool outdoor air.
Great idea — when they work.
But economizers frequently fail because of:
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Broken dampers
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Bad actuators
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Wrong settings
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Failed sensors
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Dirty outdoor air filters
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Poor wiring
What a Bad Economizer Does
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Pulls in too much hot outdoor air
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Overloads cooling system
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Ruins humidity control
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Runs fans longer
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Drives up utility bills
Here’s a conceptual reference on economizer operation:
[Outdoor Air Economizer Function Guide]
Tony’s Fix
Calibrate them.
Annually.
And replace sensors every few years.
Problem #5: Electrical Failures — The Rooftop Reality
Commercial rooftops roast electrical components:
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UV exposure
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High temp swings
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Vibration
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Moisture
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Dust
This eventually kills:
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Contactors
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Relays
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Boards
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Capacitors
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Transformers
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Motors
Symptoms
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Unit won’t start
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Breaker tripping
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Loud humming
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Short cycling
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Random shutdowns
Here’s a basic electrical failure reference:
[HVAC Electrical Component Wear Patterns]
Tony’s Fix
Inspect electrical annually.
Tighten lugs.
Replace weak components before they fail.
Problem #6: Compressor Failures — The Expensive Problem
Compressors die for one of three reasons:
1. Overheating
Usually caused by dirty coils, airflow problems, or refrigerant issues.
2. Floodback
Liquid refrigerant entering the compressor — deadly.
3. Hard starts
Electrical issues stressing the motor.
Compressor failures are expensive, time-consuming, and often not worth repairing on older units.
Here’s a conceptual resource on compressor behavior:
[Commercial Compressor Loading Dynamics]
Tony’s Prevention
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Keep coils clean
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Maintain correct airflow
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Keep refrigerant levels healthy
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Check subcool and superheat annually
Do this, and your compressor will outlive your patience.
Problem #7: Drain & Condensate Issues
Clogged drains and bad traps lead to:
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Water on the roof
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Water inside ducts
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Mold growth
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Rusted drain pans
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Overflow issues
Rooftop drains get hit by:
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Dust
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Leaves
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Bird debris
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Insect nests
Tony’s Fix
Clean the drain line every maintenance visit.
And replace rusted pans early.
Problem #8: Gas Heat Problems (If Your RTU Includes a Furnace)
Common furnace issues:
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Cracked heat exchangers
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Flame sensor failures
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Gas pressure issues
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Blower failures
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Ignition problems
Most commercial heat exchangers last 10–15 years before corrosion sets in.
Tony’s Fix
Perform annual combustion checks and clean the burner assembly.
Problem #9: Vibration, Noise & Loose Components
Rooftop units vibrate.
Constantly.
Over time this causes:
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Loose screws
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Metal rattling
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Worn fan shafts
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Belt wear
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Loose blower assemblies
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Motor imbalance
Left unchecked, vibration destroys:
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Bearings
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Motors
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Fans
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Panels
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Controls
Tony’s Fix
At every inspection, tighten hardware and check for imbalance.
Problem #10: Poor Installation — The Root of 50% of Failures
Half of the problems I fix aren't the unit’s fault.
They’re the installers'.
Common installation sins:
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Wrong airflow
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Wrong refrigerant charge
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Unlevel install
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Bad curb alignment
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Poor duct transitions
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Weak roof sealing
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Wrong gas pressure
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Undersized electrical
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Cheap wiring
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No commissioning
These shortcuts kill even the best equipment.
How to Prevent the Most Common Problems (Tony’s Complete Prevention Plan)
If you want your 10-ton light commercial packaged unit to last 15–20 years, follow this plan:
✔ Clean coils twice a year
Spring and fall.
✔ Replace filters monthly (or quarterly for high-capacity filters)
Cheap insurance.
✔ Check static pressure annually
Airflow is life.
✔ Inspect electrical connections
Loose lugs = burned boards.
✔ Verify refrigerant performance
Not just pressures.
✔ Lubricate motors (if applicable)
Don’t burn out bearings.
✔ Tune economizer
A bad economizer wrecks everything.
✔ Keep debris off the roof
Roof trash = clogged drains and dirty coils.
✔ Inspect belts and pulleys
Replace when worn.
✔ Do a full annual tune-up
Not a “check and go.” A real inspection.
Tony’s Final Word
Commercial packaged units don’t fail because they’re badly built.
They fail because they’re ignored, suffocated, abused by the environment, or installed wrong.
The most common problems — dirty coils, poor airflow, refrigerant issues, economizer failures, electrical wear, compressor death — are nearly ALWAYS preventable with real maintenance.
Do the work?
Your rooftop unit lives 15–20 years.
Ignore it?
You’ll be replacing it before year 10.
In commercial HVAC:
You don’t pay for maintenance. You pay for the lack of it.
A 10 Ton packaged and split commercial HVAC will be compared in the next blog.
