TM44 Air Conditioning Inspections Explained (12kW Rule & Prep)

If your building has air conditioning, you’ve probably heard about TM44 inspections and the 12 kW rule. But what do these terms actually mean for you? This guide explains the essentials in simple, straightforward language to help building owners, tenants, and facilities managers understand when TM44 applies, what to expect during an inspection, and how to prepare your system. Knowing your responsibilities and getting ready for an assessor can save time, avoid fines, and improve your system’s efficiency.

What TM44 air conditioning inspections are

TM44 refers to guidance used for energy assessments of air conditioning systems in the UK. It supports regulations that require certain systems to be inspected by an accredited air conditioning energy assessor.

The aim is to review how efficiently your system is operating and to suggest practical ways to reduce energy use and running costs. TM44 inspections do not replace regular servicing or safety checks, but they sit alongside them as an energy performance review.

Nothing in this article is legal advice. It is general guidance only, and you should always check your specific duties with a qualified TM44 assessor or relevant professional.

When the TM44 12 kW rule applies

The commonly cited 12 kW figure can cause confusion. It refers to the combined rated output of the air conditioning systems in a building, not just a single unit. Smaller splits can quickly add up to more than 12 kW across a site.

In simple terms, you usually need to consider a TM44 inspection if:

• The total rated output of your fixed air conditioning is above 12 kW
• The system is used for cooling indoor spaces for human comfort
• You are a building owner, landlord or tenant with control over the system

There are some exceptions and detailed rules that can apply, for example in very small premises or where systems are decommissioned. Because of this, it is sensible to speak to an accredited assessor if you are unsure whether your specific installation is in scope.

What a TM44 inspection typically looks at

A TM44 inspection is not just a quick glance at the indoor units. The assessor will usually carry out a structured review of different aspects of your air conditioning, backed up by documents and records.

Controls and system operation

Assessors pay close attention to how your system is controlled, as this has a major effect on energy use. They will look at set temperatures, time schedules, zoning and whether heating and cooling might be fighting each other in the same areas.

They may highlight simple changes, such as tightening time schedules, adjusting set points or improving zoning, that can cut energy use without affecting comfort.

Plant condition and layout

The physical condition of equipment is another key part of the inspection. The assessor will usually look at indoor and outdoor units, pipework, insulation, filters and access for maintenance.

Poorly located condensers, blocked airflow or damaged insulation can all reduce efficiency. TM44 reports often include recommendations about relocating units, improving airflow or upgrading specific components where practical.

Maintenance history and cleaning

Regular servicing affects both performance and reliability. The assessor will check maintenance records and ask how often filters, coils and drains are cleaned or replaced.

Gaps in maintenance can lead to higher energy use and shorter equipment life. While an assessor does not carry out the maintenance, they may suggest more suitable service intervals or highlight areas where your current regime could be improved.

Opportunities to improve efficiency

A TM44 report will usually include suggestions to improve efficiency. These might range from simple low cost actions to more significant upgrades.

Examples can include better control strategies, rebalancing systems, adding insulation, or considering higher efficiency equipment when you next refurbish. The recommendations are not compulsory by default, but they give you a roadmap for long term improvements.

Documents and evidence to gather before an inspection

Good preparation makes a TM44 inspection smoother and reduces the risk of gaps in the report. Ideally, you should assemble key information in advance so the assessor can focus on your system rather than chasing paperwork.

Useful items to gather include:

• An up to date asset list of all air conditioning equipment, including locations and capacities
• Recent maintenance and service records, including cleaning and filter changes
• Any commissioning sheets, previous TM44 reports or energy assessments
• Control strategy documents, BMS screenshots or example time schedules where available

It also helps to ensure plant rooms and outdoor units are accessible and safe to reach, with clear access routes and any required permits arranged in advance.

TM44 obligations compared with F-Gas

TM44 and F-Gas requirements are often mentioned together, but they cover different aspects of your system. TM44 revolves around energy efficiency assessments for qualifying systems, usually linked to the 12 kW threshold.

F-Gas rules, by contrast, are about the control of refrigerants that can affect the environment. They cover leak checking, record keeping and ensuring that refrigerant handling is carried out by qualified personnel.

Good ongoing maintenance supports both areas. Regular servicing helps reduce leaks, keeps components clean and improves efficiency, which in turn helps you manage both your F-Gas responsibilities and the performance issues that will be reviewed at a TM44 inspection.

You should always confirm your own legal duties with specialist advisers, as requirements can change and different thresholds or intervals may apply depending on refrigerant type and system size.

Common preparation mistakes to avoid

Even well run sites sometimes make avoidable errors that complicate TM44 inspections. One frequent issue is the absence of a clear asset list, which makes it harder for the assessor to confirm system capacities and locations.

Another problem is missing or incomplete service history. Without records, it is difficult to evidence how the system has been maintained, even if the actual work has been done. Keeping organised electronic or paper records is a simple fix.

Control settings can also cause trouble. It is surprisingly common to find heating and cooling operating at the same time in the same areas, wasting energy. Reviewing time schedules, occupancy patterns and set points ahead of the inspection can prevent simple issues being raised in the report.

Getting practical help with servicing and inspection readiness

Preparing for a TM44 air conditioning inspection is much easier when your system is already being maintained properly. Regular, planned servicing keeps equipment efficient, reduces breakdowns and makes it simpler to supply the documents assessors need.

If you would like support with ongoing servicing, maintenance plans or preparing your air conditioning for inspection, you can speak to the team at AGG Kent Limited. They can help you review your current setup, plan sensible maintenance and get your system ready for a TM44 assessment as part of a broader approach to efficiency.

To discuss air conditioning services or maintenance options for your property, contact AGG Kent Limited on 0775 448 7344 for friendly, professional advice tailored to your building.