Compressor Overload Issues: Causes of Breaker Tripping

Circuit breaker tripping on industrial air compressors indicates an abnormal electrical load condition that requires investigation. When motor current exceeds the protective threshold, the breaker disconnects the supply to prevent thermal damage, signalling a mismatch between mechanical demand and electrical capacity.

This article explains the electrical, mechanical, and control-related causes of compressor overloads, with reference to UK compliance requirements and diagnostic best practice. The guidance is intended to support fault isolation and safe remediation for operators and maintenance teams working with industrial compressed air systems supported by Search Air.

Analysis of Breaker Tripping Mechanisms

An air compressor trips the circuit breaker when electrical supply limitations or mechanical resistance force the motor to draw current beyond the protection threshold. This occurs due to electrical infrastructure faults, mechanical load anomalies, or electronic control interventions. Diagnosis begins by determining whether the trip occurs during startup or under load.

Electrical Infrastructure and BS 7671 Compliance

Electrical supply systems must adhere to BS 7671 (IET Wiring Regulations) to manage the high inrush current typical of industrial motors. Inadequate protective device selection or conductor sizing results in frequent nuisance tripping.

Protective Device Classification

Circuit breakers are defined by trip curves that dictate tolerance for transient current spikes.

• Type B breakers: Trip at 3 to 5 times the rated current. These are unsuitable for inductive industrial motor loads.
• Type C breakers: Trip at 5 to 10 times the rated current. These are the standards for UK industrial compressor installations.
• Type D breakers: Trip at 10 to 20 times the rated current. These are applied in high-inertia starting scenarios but require specific Earth Fault Loop Impedance Zs values to ensure compliant disconnection times under BS 7671.

Voltage Drop and Conductor Integrity

Undersized cabling increases resistance and generates a voltage drop. To maintain the required torque, the motor draws increased current as the voltage falls. BS 7671 Regulation 525.1 limits voltage drop to 5% for power circuits. Excessive drops trigger thermal trips during peak factory demand or across extended cable runs from the main distribution board.

Compressor Overload Issues

Electronic Shutdown and Diagnostic Codes

Modern units, such as the Atlas Copco GA series, integrate electronic protection that precedes physical breaker tripping. Consolidating fault data is the first step in technical troubleshooting.

Elektronikon and SMARTLINK Fault Logic

The Elektronikon controller executes an “Electronic Overload” shutdown to protect motor windings before thermal damage occurs. SMARTLINK data logs provide specific fault codes that isolate the trigger:

• Motor Over-temperature: Indicates thermal relay activation.
• Phase Loss: Indicates a disconnection in one of the three power lines.
• Overcurrent (OC): Indicates a sudden load spike or short circuit.

Mechanical Load and Thermodynamic Resistance

Mechanical resistance increases the shaft power required from the motor, directly elevating amperage draw.

Valve Failure and Starting Torque

The unloader valve must vent internal pressure to allow the motor to accelerate without a load. A valve stuck in the closed position forces a “loaded start,” resulting in a prolonged inrush period that trips the breaker. Failure of the minimum pressure valve (MPV) allows receiver tank backpressure to flow into the compressor head, leading to a locked-rotor state during the next start cycle.

Internal Binding and Oil Viscosity

Mechanical binding from worn bearings or “oil slugging”, the presence of incompressible lubricant in the compression chamber, creates high frictional resistance. In the UK, seasonal temperature drops increase lubricant viscosity. While high-performance oils like Atlas Copco Roto Xtend mitigate this, cold-start friction can still trigger overcurrent disconnections before the lubricant reaches operating temperature.

Internal Pressure Drops

Clogged consumables force the motor to work harder to overcome internal restrictions. A saturated oil separator increases the pressure drop across the element. As a general rule for rotary screw compressors, every 1 bar of additional internal pressure increases shaft power demand by approximately 7%.

Regulatory Safety and Maintenance Compliance

Repeatedly resetting a circuit breaker without technical investigation constitutes non-compliance with UK safety standards and increases the risk of catastrophic failure.

PUWER and PSSR 2000 Requirements

The Provision and Use of Work Equipment Regulations (PUWER) Regulation 5 requires equipment to be maintained in a safe condition. Non-investigated resetting of a protective device is a breach of these expectations. Furthermore, the Pressure Systems Safety Regulations (PSSR 2000) mandate that all protective devices remain in good working order. A circuit breaker acting as a surrogate for a failing pressure switch indicates a fundamental safety system failure.

Diagnostic Sequencing and Component Verification

The following sequence allows for systematic fault isolation between electrical and mechanical entities.

Resolving these imbalances prevents the unmasking of electrical faults that lead to motor burnout. Adherence to a weekly air compressor maintenance checklist ensures oil separators and filters do not contribute to excessive power draw.

Professional Diagnosis for Persistent Breaker Tripping

When a breaker trip cannot be isolated through standard maintenance checks, professional intervention is required to protect capital equipment. Search Air provides 24/7 emergency air compressor repair across Yorkshire and the East Midlands with factory-trained engineers. A structured troubleshooting flowchart can further support fault isolation during breaker trip events.

Contact us today.