Is Your 2.2 kW Air Compressor Motor Struggling? It Might Be Your Start Capacitor!
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2.2 kW Single-Phase Compressor Troubleshooting

2.2 kW Compressor Won’t Start? The Capacitor May Be One Possible Cause

A humming or non-starting 230V single-phase compressor can have several causes. A failed start or run capacitor is one possibility, but electrical supply, pressure unloading, motor protection and mechanical faults should also be considered.

Get Help Identifying the FaultCall 0121 753 3330

Humming / No StartStart & Run CapacitorsSupply & Unloader ChecksCompetent-Person Electrical WorkModel-Specific Parts

Do Not Assume the Capacitor Is the Fault

On a 2.2 kW single-phase compressor, a failed capacitor can prevent the motor from developing enough starting torque, but similar symptoms can be caused by low supply voltage, a faulty pressure switch, an unloader or check-valve problem, motor protection, a seized pump or bearing, damaged wiring, or a motor fault.

Best first step: record the compressor make, model, serial number, motor nameplate details, exact symptom and any visible capacitor markings before ordering parts.

Common Symptoms Worth Investigating

Motor Hums but Does Not TurnCan indicate insufficient starting torque, but the cause is not automatically the capacitor.Breaker or Overload TripsMay point to excessive starting current, low voltage, mechanical load or an electrical fault.Repeated ClickingCan occur when a pressure switch, overload device or control component repeatedly attempts to restart.Slow or Laboured StartingMay be associated with supply voltage, capacitor condition, pressure remaining on the pump or mechanical resistance.Visible Capacitor DamageBulging, cracking, leakage or overheating are reasons to stop using the machine and have the component checked.Unexpected OverheatingA stalled or repeatedly restarting motor can overheat quickly and should not be repeatedly reset.

What the Capacitors Do

Many single-phase induction motors use capacitors to create the phase shift needed for starting and/or running. The exact arrangement varies by motor design.

Start Capacitor

Provides additional starting torque for a short period and is normally removed from the circuit by the motor’s start mechanism once the motor accelerates.

Run Capacitor

Remains in circuit during normal operation on motors designed to use one. It has a different duty and specification from a start capacitor.

Do not substitute one for the other. Start and run capacitors have different operating duties. Use the exact type and electrical specification required by the motor manufacturer.

Electrical Safety Comes First

Capacitors can retain a hazardous electrical charge after power has been disconnected. Compressor motor circuits can also involve high starting currents and stored mechanical or pneumatic energy.

  • Disconnect and securely isolate the electrical supply before covers are removed.
  • Depressurise the compressor system where required by the manufacturer’s service procedure.
  • Do not touch capacitor terminals or exposed wiring unless you are competent to work safely on the equipment.
  • Do not attempt improvised capacitor-discharge methods.
  • Capacitor discharge, electrical testing and motor wiring should be carried out using an appropriate safe method by a competent person.

How a Capacitor Should Be Checked

A visual inspection can identify obvious physical damage, but electrical condition should be checked with suitable test equipment and an appropriate safe isolation/discharge procedure.

Check What It Can Tell You
Part markings Confirms capacitance, voltage rating, capacitor type and other manufacturer information.
Visual condition Bulging, leakage, cracking, heat damage or damaged terminals may indicate failure.
Capacitance measurement A competent person can compare the measured value with the component’s stated tolerance.
Motor circuit diagnosis Checks whether the capacitor, start switch, relay, wiring or another component is responsible for the fault.

Use the value printed on the existing component or confirmed by the motor manufacturer. Motor power alone is not enough to choose a capacitor safely.

Choosing the Correct Replacement Capacitor

A 2.2 kW motor does not have one universal capacitor size. Different motors can use different capacitance values, voltage ratings and start/run arrangements.

  • Match the exact capacitor type: start or run.
  • Match the required capacitance and tolerance.
  • Use the correct AC voltage rating specified for the motor circuit.
  • Confirm terminal style and physical dimensions.
  • Check the motor make, model and wiring arrangement.
  • Where uncertain, send the original capacitor markings and motor nameplate details for identification.

Current Tanair Capacitor Options

These products are examples from the current Tanair range. They are not interchangeable simply because they are associated with 1.5 kW or 2.2 kW motors. Confirm the exact motor requirement before ordering.

Tanair 50 microfarad run capacitor 450VAC50uF +5% Run Capacitor · 450VACSuitable for compatible 1.5 kW / 2.2 kW 230V single-phase motors where this exact run-capacitor specification is required.View product →
Tanair 60 microfarad run capacitor 450VAC60uF +5% Run Capacitor · 450VACRun capacitor for compatible 1.5 kW / 2.2 kW 230V single-phase motors requiring this exact value.View product →
Tanair 230 to 315 microfarad start capacitor 250V230–315uF Start Capacitor · 250VFor compatible Tanair 2.2 kW 230V single-phase motor applications where this exact start-capacitor specification is required.View product →
Tanair 200 to 250 microfarad start capacitor 250V200–250uF Start Capacitor · 250VFor compatible Tanair 2.2 kW 230V single-phase motor applications requiring this specified range.View product →
Tanair 200 microfarad start capacitor 250V200uF Start Capacitor · 250VFor compatible 1.5 kW / 2.2 kW 230V single-phase motor applications requiring a 200uF start capacitor.View product →
Tanair 40 microfarad run capacitor 450VAC40uF +5% Run Capacitor · 450VACCurrent Tanair run capacitor specified for compatible 1.5 kW 230V single-phase motors.View product →

Other Reasons a 2.2 kW Compressor May Not Start

Supply Voltage / ConnectionExcessive voltage drop, poor connections or an unsuitable supply can prevent reliable starting.Pressure SwitchA faulty or incorrectly operating switch may fail to energise the motor correctly.Unloader or Check ValveResidual head pressure can make a healthy motor struggle to restart.Motor ProtectionA thermal overload may trip because of overheating, overload or another electrical/mechanical problem.Mechanical ResistancePump, bearing or drive problems can increase starting load significantly.Motor Start MechanismCentrifugal switches, relays or internal motor components can fail independently of the capacitor.

Do Not Use “Starts If I Spin It” as a DIY Live Test

Manually spinning pulleys or other moving parts as part of a live-start experiment introduces unnecessary risk. Mechanical freedom can be checked only with the machine securely isolated and in accordance with the manufacturer’s service procedure.

If electrical power is needed for diagnosis, testing should be carried out by a competent person using suitable instruments and safe working methods.

Preventing Repeat Starting Problems

  • Keep motor cooling openings and compressor ventilation clear.
  • Use the electrical supply and cable arrangement specified by the manufacturer.
  • Avoid repeated short-cycling.
  • Maintain the pressure switch, unloader and non-return valve where applicable.
  • Follow the manufacturer’s service schedule rather than a generic annual interval.
  • Drain and maintain the receiver in accordance with the manufacturer’s instructions and applicable pressure-system requirements.

What to Send Us for Part Identification

Information Why It Helps
Compressor make & model Identifies the machine family and likely motor arrangement.
Serial number Helps distinguish revisions or production variants.
Motor nameplate photo Provides voltage, phase, power and motor reference information.
Capacitor markings Shows capacitance, voltage, type and tolerance.
Clear wiring-area photos Useful for part identification without asking you to disturb wiring.
Fault symptoms Humming, tripping, clicking, slow starting or overheating help narrow the diagnosis.

Related Support

Compressor Servicing & RepairsPlanned maintenance, diagnosis and repair support for compressed-air equipment.Explore service →Parts IdentificationSend motor, compressor and capacitor details so the correct part can be checked.Contact us →Help & Advice CentreBrowse practical compressed-air guides, calculators and support information.Browse advice →

2.2 kW Compressor Starting FAQs

Does humming mean the start capacitor has failed?

Not necessarily. A capacitor fault is one possibility, but supply, pressure unloading, motor protection, mechanical resistance and other electrical faults can produce similar symptoms.

What capacitor size does a 2.2 kW compressor need?

There is no universal value. Use the exact capacitor specification from the existing component, motor documentation or manufacturer.

Can I replace a start capacitor with a run capacitor?

No. They have different duties and must not be treated as interchangeable.

Can I discharge a capacitor with a screwdriver?

Improvised discharge methods are not recommended. Capacitors can retain hazardous charge, so discharge and testing should be carried out using an appropriate safe method by a competent person.

Why does the compressor struggle to restart when the receiver is pressurised?

A faulty unloader or check-valve arrangement can leave pressure against the pump during restart, increasing the motor’s starting load.

Should I keep resetting a compressor that hums or trips?

No. Repeated failed starts can overheat the motor and may worsen the fault. Stop and diagnose the cause.

Can Compressed Air Systems UK identify the correct capacitor?

Yes. Send the compressor model, serial number, motor nameplate and clear photos of the existing capacitor markings.

Not Sure Which Capacitor or Fault You Have?

Send us a clear photo of the motor nameplate and capacitor markings together with the compressor model, serial number and fault symptoms. We can help identify the likely part or advise whether professional diagnosis is the better next step.

Send Us the DetailsCall 0121 753 3330

Compressed Air Systems UK · Unit 15, Fortnum Close, Birmingham, B33 0LG

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