TM44 air conditioning inspections: 12 kW rule and how to prepare

TM44 air conditioning inspections explained: the 12 kW rule and how to prepare

If your premises uses air conditioning, understanding TM44 air conditioning inspections is essential. This guide explains what TM44 requires, how the often‑quoted 12 kW threshold works, what assessors look for, and practical steps to prepare your installation. Clear preparation saves time, improves energy use and reduces the likelihood of costly follow‑up work.

What TM44 air conditioning inspections are

TM44 is the technical guidance used for energy assessments of fixed air conditioning systems in the UK. An accredited air conditioning energy assessor carries out a TM44 inspection to review a system’s energy performance and recommend measures to improve efficiency. These inspections complement, but do not replace, routine safety servicing and maintenance.

Nothing in this article is legal advice. Use it as general guidance and confirm your specific duties with an accredited TM44 assessor or other qualified professional.

When the 12 kW rule applies

The 12 kW figure often causes confusion. It refers to the combined rated cooling output of all fixed air conditioning equipment in a building, not just the capacity of a single indoor unit. Multiple small split systems can quickly add up and bring a building into scope.

In practice you will typically need to consider a TM44 inspection when:

• the total rated cooling output of fixed systems in the building exceeds 12 kW,
• the system is used for cooling indoor spaces occupied for human comfort, and
• you are a building owner, landlord or tenant with control over the equipment.

There are exceptions and detailed rules for particular cases — for example very small premises, systems that are permanently decommissioned, or unusual building use. If you are unsure whether your installation is in scope, consult an accredited assessor for clarification.

What an assessor will inspect

A TM44 inspection is a structured review, combining a site survey with documentary checks. Assessors assess how the system is used, its condition and maintenance history, and the opportunities to improve efficiency.

Controls and system operation

Controls are a primary focus because poor control strategy is a common source of wasted energy. Inspectors review set temperatures, schedules, zoning and any evidence that heating and cooling are operating simultaneously within the same spaces. Simple changes to time schedules, set points or zoning can deliver immediate energy savings without compromising occupant comfort.

Plant condition and layout

Assessors examine indoor and outdoor units, pipework, insulation, filters and access for maintenance. Issues such as poorly sited condensers, blocked airflow, corroded components or damaged insulation reduce efficiency and can shorten equipment life. Reports commonly recommend relocating equipment, improving airflow, or targeted component upgrades where practical.

Maintenance history and cleaning

A clear maintenance record is important. Inspectors will check service logs for filter changes, coil cleaning, drain clearance and other routine tasks. Gaps in maintenance make it harder to demonstrate that a system has been properly cared for and often appear in the report as items needing attention.

Opportunities for efficiency improvements

TM44 reports include practical recommendations ranging from low‑cost operational changes to longer‑term replacement strategies. Typical suggestions include improved control strategies, rebalancing plant, adding insulation or planning more efficient equipment at the next replacement cycle. These recommendations are advisory, but they provide a practical roadmap for lowering energy use.

Documents and evidence to prepare

Preparing documentation in advance makes the inspection run smoothly and reduces the chance of incomplete findings. Useful items to assemble include:

• an asset list of all fixed air conditioning equipment with locations and rated capacities,
• recent maintenance and service records, including filter changes and coil cleanings,
• commissioning sheets and any previous TM44 or energy assessment reports,
• control strategy documents, BMS screenshots or example time schedules.

Ensure plant rooms and outdoor units are accessible and safe to reach, and arrange any required permits or site access ahead of the visit.

TM44 versus F‑Gas: how they interact

TM44 and F‑Gas requirements are complementary but focus on different issues. TM44 addresses energy efficiency and operational performance, whereas F‑Gas regulations govern refrigerant handling, leak checking and record keeping to protect the environment. Good maintenance practices support compliance with both sets of requirements: well‑maintained equipment reduces leaks, improves performance and simplifies record keeping.

Always verify legal obligations with specialist advisers, as thresholds and intervals can vary depending on refrigerant type and system size.

Common preparation mistakes to avoid

Even well‑managed sites make avoidable errors that complicate inspections. Frequently seen problems include:

• a missing or incomplete asset list, which makes capacity verification time‑consuming,
• poorly organised or absent service histories, preventing evidence of past maintenance,
• control settings that allow heating and cooling to run together, wasting energy.

Addressing these items before the assessor arrives will usually reduce the number of recommendations and speed up the overall process.

Getting practical help with servicing and inspection readiness

Regular planned servicing makes TM44 preparation straightforward. Routine maintenance keeps systems efficient, reduces breakdowns and ensures you have the documentation assessors need.

If you would like assistance with ongoing servicing, maintenance plans or preparing your air conditioning for a TM44 assessment, our team at AGG Kent can help. We offer tailored support to review your installation, optimise control strategies and get documentation in order.

To discuss air conditioning services, maintenance or inspection readiness, contact AGG Kent on 0775 448 7344 or visit our air conditioning services page. For general enquiries or to book an inspection, use our contact page.

For more guidance on maintaining commercial plant and reducing operating costs, see our resources in the blog or explore our preventative maintenance plans for ongoing support.