Leak check frequency: working out your CO2e and your schedule

The calculation

CO2e (tonnes) = refrigerant charge (kg) x GWP / 1000

You need two figures, and both are on the outdoor unit’s nameplate:

1. The refrigerant type – R410A, R32, R134a, R407C and so on.
2. The charge quantity in kilograms.

The GWP for each refrigerant is published in the regulation and is a fixed figure. Multiply, divide by a thousand, and you have the system’s CO2e in tonnes.

What the thresholds do

The regime works in bands. Below the lowest threshold there is no mandatory periodic leak checking at all. Above it, checking is required, and the interval shortens as CO2e rises through successive bands.

We are deliberately describing the structure rather than quoting the specific figures and intervals, because they are set in regulation, they have changed, and a number remembered from a training course several years ago is exactly how people end up non-compliant. Check the current gov.uk guidance, or ask us to calculate it against the rules as they stand.

Worked through, conceptually

1. Find the nameplateOn the outdoor unit. Photograph it – you will want this again.
2. Note the refrigerant typeWritten as R followed by a number.
3. Note the charge in kilogramsSometimes given in grams – check the units.
4. Add any additional chargeFrom commissioning records, where pipe runs required it.
5. Look up the GWPFor that refrigerant, from the current published values.
6. Multiply and divide by 1000Giving tonnes of CO2e.
7. Compare against the current thresholdsWhich gives you the required interval, or confirms no mandatory checking applies.
8. Check whether automatic leak detection is requiredAnd whether fitting it voluntarily would extend your interval usefully.
9. Record the resultPer system, in the logbook. This is the calculation an inspector would want to see.

Repeat for every system on the site. It is a short job per unit and it is the foundation of everything else.

Why identical-looking systems differ

This is the part that surprises people, and it is worth understanding because it affects replacement decisions.

Refrigerant GWPs vary by a large factor. A system charged with a high-GWP refrigerant reaches any given CO2e threshold at a much smaller physical quantity than a system using a lower-GWP one.

Practical consequences:

• Two visually identical units with the same physical charge can fall either side of a threshold purely because of refrigerant type.
• Replacing old plant with equivalent capacity on a modern low-GWP refrigerant can move a system below a threshold, reducing your ongoing compliance burden – which is a genuine and often unconsidered benefit of replacement.
• A larger system on a low-GWP refrigerant may have fewer obligations than a smaller one on a high-GWP refrigerant.
• Adding a system to a site does not aggregate – each system is assessed on its own CO2e, not the site total.

That last point matters. The threshold applies per system, not per site. Ten small splits each below the threshold have no mandatory leak checking; one VRF system with the same total charge may have quarterly checking.

Automatic leak detection

Above a defined CO2e threshold, a fixed automatic leak detection system is mandatory. Below it, fitting one voluntarily extends the permitted interval between manual checks.

Worth knowing:

• It must alert the operator or a service company when a leak is detected – a detector that alarms locally in an empty plant room is of limited use.
• The detection system itself must be checked at defined intervals to confirm it is functioning.
• It does not remove the manual checking obligation, it extends the interval.
• On borderline systems, fitting one voluntarily can be economically sensible, halving the number of manual check visits over the plant’s life. Worth doing the arithmetic.

What a leak check actually involves

It is not a visual inspection and it is not the same as a service.

• Carried out by a certified person working for a certified company.
• Using an appropriate method – a calibrated electronic leak detector, or an indirect method based on system parameters where the standards permit it.
• Covering the parts most prone to leakage – joints, valves, seals, flares, service ports, and areas subject to vibration.
• Recorded in the system logbook with the date, the method, the result and who carried it out.
• Followed by repair without undue delay where a leak is found, and a re-check within the defined period afterwards to verify the repair.

A maintenance visit is not automatically a leak check, and a leak check is not a service. Both need to happen, both need recording, and conflating them is a common source of gaps – see what an F-Gas logbook must contain.