Why Air Conditioning Systems Fail During Heatwaves (And How to Prevent It)
- Przemysław Chmurski
- Jun 30
- 5 min read
Why Air Conditioning Systems Fail During Heatwaves (And How to Prevent It)
The recent UK heatwaves placed commercial air conditioning systems under immense pressure.
Across offices, retail spaces, restaurants, schools, gyms and commercial buildings, air conditioning units were forced to run continuously as temperatures climbed well above seasonal averages.
While many systems continued operating without issue, others struggled to keep up. Businesses reported uncomfortable working environments, rising energy bills and, in some cases, complete air conditioning failures.
The reality is that heatwaves rarely cause air conditioning systems to fail overnight—they expose existing weaknesses that have often been developing for months.
Whether your system simply couldn't keep up or stopped working altogether, understanding why it happened can help prevent the same issues during the next period of extreme weather.
Why Heatwaves Put Air Conditioning Systems Under Pressure
Air conditioning systems are designed to remove heat from inside a building and release it outdoors.
As outside temperatures increase, this process becomes significantly more demanding.
During a heatwave:
Cooling systems run for much longer periods
Compressors operate almost continuously
Outdoor condensers struggle to reject heat efficiently
Internal heat gains increase due to occupancy and equipment
Electricity consumption rises
A well-maintained system can usually cope with these conditions.
However, if maintenance has been neglected or components are already underperforming, extreme temperatures can quickly expose those weaknesses.
Why Air Conditioning Systems Fail During Heatwaves
Dirty Air Filters
Air filters are designed to protect the system while maintaining adequate airflow.
Over time they collect dust, dirt and debris.
Restricted airflow means the system must work harder to achieve the desired temperature.
During hot weather, this additional strain often leads to poor cooling performance and increased energy consumption.
Regular filter cleaning is one of the simplest ways to improve efficiency.
Dirty Condenser Coils
Outdoor condenser units remove heat from the refrigeration cycle.
If the coils become clogged with dirt, leaves or airborne debris, the system cannot reject heat effectively.
This causes:
Reduced cooling performance
Higher operating pressures
Increased compressor strain
Higher electricity costs
Routine servicing helps keep condensers operating efficiently throughout the summer.
Low Refrigerant Levels
Refrigerant carries heat through the air conditioning system.
If refrigerant levels are low due to a leak, cooling capacity is reduced significantly.
Common signs include:
Warm air from vents
Longer cooling times
Ice forming on pipework
Increased running costs
Low refrigerant should always be investigated by a qualified engineer.
Read our related guide:
Poor System Controls
One of the most overlooked causes of poor performance isn't mechanical—it's operational.
Many buildings operate with:
Incorrect temperature setpoints
Systems running outside occupancy hours
Simultaneous heating and cooling
Poor zoning strategies
These issues become particularly noticeable during heatwaves when cooling demand is highest.
A review of system controls can often improve performance without replacing equipment.
Blocked Outdoor Units
Air conditioning condensers require unrestricted airflow.
Unfortunately, outdoor units often become partially blocked by:
Vegetation
Rubbish
Packaging
Temporary storage
Fencing or screening
Without adequate airflow, cooling efficiency drops dramatically.
A simple inspection can often identify issues before they impact system performance.
Aging or Undersized Equipment
Some systems simply weren't designed for today's cooling demands.
Changes in occupancy, office layouts or equipment loads can leave older systems struggling during periods of extreme heat.
Heatwaves often reveal buildings where air conditioning capacity no longer matches operational requirements.
Signs Your Air Conditioning Needs Attention
Many systems provide warning signs before they fail completely.
Look out for:
Uneven temperatures throughout the building
Warm air instead of cool air
Unusual noises
Continuous operation
Higher electricity bills
Poor humidity control
Reduced airflow
These issues should never be ignored, particularly before another period of hot weather.
The Hidden Cost of Poor Air Conditioning Performance
A struggling air conditioning system affects far more than comfort.
Poor performance can lead to:
Reduced staff productivity
Uncomfortable working environments
Customer dissatisfaction
Increased energy costs
Equipment downtime
Emergency repair bills
For businesses that rely on comfortable indoor environments, poor HVAC performance quickly becomes a business issue—not just a maintenance issue.
Why Planned Maintenance Makes the Difference
The best-performing air conditioning systems aren't necessarily the newest.
They're the best maintained.
Routine servicing helps:
Improve energy efficiency
Reduce breakdowns
Extend equipment lifespan
Maintain consistent cooling
Identify faults before they become failures
Reduce emergency repair costs
Planned maintenance is one of the simplest ways to improve system reliability before temperatures begin to rise.
Learn more about our Commercial Air Conditioning Services.
Air Conditioning Performance and Compliance
Keeping systems cool isn't the only priority.
Commercial buildings also have legal responsibilities regarding HVAC performance and efficiency.
Depending on your building and equipment, this may include:
TM44 Air Conditioning Inspections
Planned maintenance
F-Gas compliance
Energy efficiency reviews
Understanding these requirements helps businesses maintain reliable systems while remaining compliant.
Related reading:
What Should You Review After the Heatwave?
Now temperatures have fallen, it's the perfect opportunity to review how your air conditioning system performed.
Ask yourself:
✔ Did the building remain comfortable?
✔ Were some areas warmer than others?
✔ Did energy costs increase significantly?
✔ Was cooling performance consistent?
✔ Have filters and coils been serviced recently?
✔ Is planned maintenance in place before the next heatwave?
Reviewing performance now provides valuable insight before temperatures rise again.
Preparing for the Next Heatwave
Extreme temperatures are becoming more common across the UK.
Rather than reacting when systems struggle, businesses should prepare in advance by:
Booking annual servicing
Cleaning filters and condensers
Reviewing controls and scheduling
Checking refrigerant performance
Planning maintenance before summer
These relatively small actions can make a significant difference during periods of extreme demand.
How RSI Professional Can Help
At RSI Professional, we help commercial clients maintain efficient, reliable air conditioning systems throughout the year.
Our services include:
Commercial air conditioning servicing
Planned maintenance
Fault diagnosis and repairs
Performance optimisation
Energy efficiency improvements
Preventative maintenance programmes
Whether you manage a single office or multiple commercial buildings, proactive servicing helps keep your systems performing when they're needed most.
Explore our Commercial Air Conditioning Services to learn more.
Heatwaves Don't Cause HVAC Problems—They Reveal Them
Every period of extreme heat provides an opportunity to better understand how your building performs.
If your air conditioning system struggled this summer, don't wait until the next heatwave to investigate why.
Reviewing system performance now can improve comfort, reduce energy costs and help avoid unexpected breakdowns when temperatures inevitably rise again.
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