Compressor Overheating or Tripping Off? Here’s Why

Compressor overheating or unexpected tripping causes unplanned shutdowns that interrupt production, increase operating costs, and risk equipment damage. Understanding whether a fault is electrical or thermal, and identifying its root cause, is essential to restoring compressed air systems quickly and safely.

This guide explains the most common reasons compressors overheat or trip, how different systems respond to heat, and what preventative actions reduce risk. It is provided by Search Air, a UK distributor and service partner for Atlas Copco compressors, supporting businesses across Yorkshire, the East Midlands, and Lincolnshire.

What Is the Difference Between a “Trip” and a “Shutdown”?

These terms are distinct events triggered by specific safety mechanisms.

A Trip: An immediate electrical disconnection triggered by a safety relay or circuit breaker. This occurs in response to current spikes or short circuits to prevent motor burnout or fire.
A Shutdown: A controlled stop initiated by the central controller. This occurs when sensors detect parameters (such as temperature or pressure) exceeding pre-set safety thresholds to prevent mechanical damage.

Why Do Compressors Overheat?

Compressors generate significant thermal energy. Approximately 80% to 90% of the electrical energy used by the motor converts into heat, which must be rejected by the cooling system. If the heat generation rate exceeds the rejection rate, the internal temperature rises rapidly.

On Atlas Copco machines, the Elektronikon controller will normally warn operators at approximately 110°C (depending on the specific model). If the temperature continues to rise, typically reaching 120°C, the system triggers a shutdown to protect the airend. This often displays the fault code Element Outlet Temp High.

Compressor Overheating or Tripping Off

How Does Ventilation Cause Overheating?

Inadequate ventilation is a primary cause of overheating. If the compressor room is undersized or vents are obstructed, hot exhaust air recirculates into the intake.

Airflow: A rotary screw compressor requires approximately 200–250 m³/h of fresh airflow per kW of installed power.
Ambient Temperature: Most UK systems are designed for a maximum ambient temperature of 35°C, unless otherwise specified by the manufacturer. Operating consistently above 30°C increases overheating risk.
Louver Size: Sizing must account for “free area.” The actual open space for airflow is typically only 30% to 60% of the total face area.
Ducting: Exhaust ducting must lead directly outdoors to prevent hot air from leaking back into the intake.

Which Mechanical Failures Cause Overheating?

Mechanical components degrade over time, impairing the cooling or lubrication subsystems.

Cooling Subsystem

Cooler Fouling: Dust and oil mist form a matrix on cooler fins, insulating them. This prevents heat rejection even if the fan is operational.
Thermal Bypass Valve: This valve regulates oil temperature via a wax element. If the element fails, it typically sticks in the “cold” position, bypassing the cooler and causing rapid overheating.

Lubrication Subsystem

Oil Stop Valve: This valve must open immediately upon startup. Failure causes the airend to run dry, resulting in an instant temperature spike.
Minimum Pressure Valve (MPV): The MPV maintains internal pressure to ensure oil circulation. If it sticks open, oil flow drops, leading to overheating.
Blocked Scavenge Line: If this line blocks, oil is pushed into the air network. The resulting low oil level in the sump causes temperature elevation.

Airflow and Rotating Parts

Blocked Inlet Filter: A choked air filter restricts intake, forcing the compressor to work harder and increasing operating temperatures.
Bearing Wear: Worn bearings increase friction and mechanical drag, causing the motor to draw excess power and trigger an overload.

For more details on these mechanical issues, read our guide on the Most Overlooked Causes of Air Compressor Downtime.

Why Do Electrical Issues Cause Trips?

Electrical diagnostics must only be carried out by a competent engineer under strict Lockout/Tagout (LOTO) procedures. Bypassing safety trips to force a machine to run is illegal under PUWER 1998.

Voltage Imbalance: A voltage imbalance of just 2% between phases can cause a significant current spike in the motor, creating hot spots in the windings.
Overload Relay: This device protects the motor from excessive power draw. It trips if the motor is overloaded due to high pressure or mechanical blockage.
Thermistor Trip: Sensors embedded in the motor windings measure heat directly. A trip indicates the motor is physically too hot.
VSD Faults: Variable Speed Drive (VSD) units include internal protection. They may shut down due to drive overheating, fan failure, or power surges.

How Do Different Models Handle Heat?

Cooling strategies vary by compressor design and application.

Atlas Copco GA Series: These utilise large air/oil coolers for robust performance. They maintain stable temperatures unless ambient conditions exceed 46°C.
GA VSD/VSD+: Variable Speed Drive models reduce motor speed during low demand, generating less heat compared to fixed-speed units running unloaded.
Piston Compressors (LE/LT): These air-cooled units rely on flywheel fans. They are not designed for continuous 24/7 operation; exceeding a 60–70% duty cycle leads to overheating.
Oil-Free (Z Series): Often water-cooled, these units are highly effective in hot environments as they rely less on ambient airflow for cooling.

Modern systems utilise technology to assist with thermal management. SMARTLINK monitoring tracks temperature trends to identify slow rises before a breakdown occurs.

Learn more about these tools in our article on Advanced Air Compressor Monitoring Systems.

What Are the Regulatory Implications?

A shutdown due to overheating can have regulatory implications.

PSSR 2000: Serious overheating events can weaken pressure vessels. The Written Scheme of Examination (WSE) requires systems to remain within safe operating limits.
PUWER 1998: Equipment must be maintained in safe working order. Ignoring warning signs violates this regulation.
EAWR 1989: Electrical work must be conducted safely. Work on live panels requires strict adherence to safety precautions.

How Can You Prevent Overheating?

Routine checks can prevent the majority of thermal and electrical faults.

Check the Display: Monitor for early warnings prior to shutdown events.
Inspect the Coolers: Check cooler fins weekly for dust accumulation.
Monitor Room Temp: Verify intake air temperature is below 35°C.
Sample the Oil: Quarterly sampling detects varnish formation early. Always use genuine Atlas Copco Compressor Parts to ensure correct oil viscosity.
Change the Separator: Replace the separator before the pressure drop becomes excessive.
Fix Leaks: Reducing system leaks lowers the duty cycle on the compressor, reducing heat generation.

Expert Support for Compressor Failures

Diagnosing a tripping compressor requires a systematic assessment of mechanical, electrical, and thermal systems. Search Air provides 24/7 emergency breakdown support across Yorkshire, the East Midlands, and Lincolnshire. Our engineers are trained to identify root causes efficiently, ensuring compliance and restoring reliability.

For professional assistance with system efficiency, consider a Compressed Air Leak Detection survey. To ensure your system remains reliable year-round, consider one of our tailored Air Compressor Service Plans.