Air-conditioning assessment

Whether you have a single wall-mounted "split" unit or a multi-room system, regular assessments are often a condition of your manufacturer’s warranty. This guide covers what to expect when a qualified engineer visits your home and the typical costs involved in 2025.

What Does the Work Involve?

• Visual Inspection: Checking the physical condition of indoor units, outdoor condensers, and mounting brackets for signs of wear or corrosion.
• Electrical Safety: Testing the isolator switches, fuses, and internal wiring to ensure the system is drawing power safely.
• Performance Testing: Measuring airflow and the "temperature split" (the difference between air entering and leaving the unit) to confirm it is cooling correctly.
• Refrigerant Check: Assessing gas pressures and checking the compressor operation to ensure there are no leaks in the sealed system.
• Drainage Audit: Inspecting condensate pumps and gravity drains for blockages, leaks, or mould growth that can cause water damage.
• Reporting: Providing a written summary of findings, including digital photos and recommendations for any necessary repairs or energy-saving upgrades.

Typical Costs

Prices vary based on your location in the UK, with London and the South East typically seeing higher labour rates. The age of your system also impacts cost, as older units using obsolete refrigerants may require more specialist testing equipment.

How Long Does It Take?

• Single Split System: 1 to 1.5 hours for a standard domestic wall-mounted unit.
• Multi-Split System (3-5 rooms): 2 to 4 hours, as each indoor unit must be tested individually.
• Ducted/Concealed Systems: 3+ hours, depending on access to loft spaces or ceiling voids.
• Leak Detection: An additional 1 to 2 hours if the initial assessment suggests a loss of refrigerant pressure.

DIY or Professional?

While you can safely clean the external plastic casing and dust the reachable filters yourself, all technical assessments must be carried out by a professional. It is illegal in the UK for an unqualified person to work on the refrigerant circuit of an air conditioning system.

Only hire engineers who are F-Gas certified. Handling fluorinated gases without the correct credentials is a criminal offence and will void your home insurance.

Choosing the Right Tradesperson

• Check Credentials: Ensure the engineer or firm is registered with an F-Gas body such as REFCOM or Quidos.
• Insurance: Verify they hold valid Public Liability insurance (minimum £2 million is standard).
• Specialism: Ask if they have experience with your specific brand (e.g., Daikin, Mitsubishi, Panasonic).

Questions to ask:

• "Will you provide a full F-Gas logbook entry or a digital report after the visit?"
• "Does your call-out fee include the first hour of labour?"
• "Are you equipped to work at height if my outdoor unit is on a high wall?"
• "If a leak is found, can you provide a fixed quote for the repair today?"

UK Regulations

• F-Gas Regulations 2015: Mandatory certification for anyone installing, maintaining, or assessing AC systems containing refrigerant.
• Part P (Building Regulations): Covers the electrical safety of the installation; any new wiring must be compliant.
• Energy Performance of Buildings: Systems with an effective rated output of more than 12kW require a mandatory TM44 inspection every five years (mostly applies to very large homes or commercial sites).

Common Problems

• Refrigerant Leaks: Often caused by vibration or poor initial installation; results in the unit blowing warm air.
• Blocked Condensate Drains: Sludge or mould buildup can cause water to leak from the indoor unit down your walls.
• Faulty Capacitors: A common electrical failure that prevents the outdoor compressor from starting up.
• Dirty Heat Exchangers: Dust buildup on the outdoor coils forces the system to work harder, significantly increasing your electricity bills.

Frequently Asked Questions

How often should I have my air conditioning assessed?

For most UK homes, an annual assessment is sufficient. However, if you use your system for heating in the winter as well as cooling in the summer, a bi-annual check is recommended.

Why is my air conditioning unit making a bubbling noise?

This usually indicates a blockage in the condensate drain line or, more seriously, a leak in the refrigerant pipework. An assessment will identify the exact cause before it leads to a total system failure.

Will an assessment help lower my energy bills?

Yes. An inefficient system can use up to 30% more electricity. Cleaning the coils and ensuring the correct gas pressure allows the system to reach the desired temperature much faster.

My AC smells like damp socks; what is that?

This is often "Dirty Sock Syndrome," caused by bacteria and mould growing on the indoor evaporator coils. A professional assessment includes a deep clean with specialist antimicrobial chemicals to kill the odour.

What is the difference between an assessment and a service?

An assessment is a diagnostic health check to find faults. A service usually includes the assessment plus proactive maintenance, such as deep-cleaning filters and chemical flushes of the drainage system.