3.2 CO2-Equivalent Calculation & Leak-Testing Thresholds

The shift from measuring refrigerant charges strictly by their physical weight (kilograms) to evaluating their environmental impact via Carbon Dioxide Equivalent (CO2e) was one of the most critical changes introduced by EU Regulation 517/2014. Because different fluorinated greenhouse gases have vastly different Global Warming Potentials (GWP), treating 10 kg of R-134a the same as 10 kg of R-404A fails to account for the true climate damage a leak would cause. The CO2e metric solves this by standardizing the impact of all F-gases against carbon dioxide. Understanding how to calculate CO2e and how it dictates mandatory leak-testing frequencies is essential for Category I engineers.

The CO2 Equivalent (CO2e) Formula

Carbon Dioxide Equivalent is a measure used to compare the emissions from various greenhouse gases based upon their global warming potential. The GWP of carbon dioxide is always 1. If a refrigerant has a GWP of 2000, it means that releasing one kilogram of that refrigerant traps 2000 times more heat in the atmosphere than releasing one kilogram of CO2.

The formula to convert the physical charge of a system (in kilograms) into tonnes of CO2 equivalent is:

CO2e (in tonnes) = (Weight of Refrigerant in kg × GWP of Refrigerant) ÷ 1000

Alternatively, if you know the threshold in tonnes of CO2e and need to find the maximum allowed charge in kilograms, the formula is rearranged:

Maximum Charge (kg) = (Threshold in Tonnes CO2e × 1000) ÷ GWP of Refrigerant

Worked Example 1: Calculating CO2e

A supermarket pack system holds 45 kg of R-404A. The GWP of R-404A is 3922. What is the CO2e of this system?

• Weight = 45 kg
• GWP = 3922
• Calculation: (45 × 3922) / 1000 = 176,490 / 1000 = 176.49 tonnes CO2e. Despite holding a relatively moderate physical charge, this system represents a massive climate risk.

Worked Example 2: Determining Maximum Charge for a Threshold

You are installing a new R-32 air conditioning system (GWP of R-32 is 675) and want to know how many kilograms you can install before hitting the 50 tonnes CO2e threshold that mandates more frequent leak checks.

• Target CO2e = 50 tonnes
• GWP = 675
• Calculation: (50 × 1000) / 675 = 50,000 / 675 = 74.07 kg. You can install up to 74.07 kg of R-32 before crossing the 50-tonne CO2e boundary.

Leak-Testing Frequencies and CO2e Bands

The Retained F-Gas Regulation establishes mandatory, periodic leak-testing intervals based solely on the CO2e of the system's charge. As the environmental risk increases, the testing must become more frequent. There are three primary tiers:

Note: Systems with a charge of 500 tonnes CO2e or more are legally required to have a fixed, automatic leak detection system installed. Therefore, in practice, their manual testing frequency is usually halved to every 6 months, but the detection system itself must be checked every 12 months.

The Hermetic Exemption

There is an important exemption for hermetically sealed equipment (such as domestic refrigerators, small self-contained display cabinets, or plug-in water coolers). For standard split systems or built-up field installations, the leak testing requirements begin at 5 tonnes CO2e. However, if the equipment is hermetically sealed and correctly labeled as such by the manufacturer, the mandatory leak-testing threshold is doubled to 10 tonnes CO2e.

To qualify for this exemption, the system must have a tested leak rate of less than 3 grams per year under a pressure of at least a quarter of its maximum allowable pressure, and all its refrigerant-containing parts must be permanently sealed by welding, brazing, or a similar permanent connection. Valves and capped service ports are permitted, provided they are securely sealed.

Practical Application on the Job

As an engineer, you must check the system logbook or the equipment data plate upon arrival at a site. If the data plate only lists the charge in kilograms and the refrigerant type, you must manually calculate the CO2e to determine the correct testing interval. If you service an R-410A (GWP 2088) system with a 3 kg charge:

• CO2e = (3 × 2088) / 1000 = 6.26 tonnes CO2e. Because 6.26 is greater than 5, this system requires a mandatory leak test at least once every 12 months. If the operator lacks a logbook for this system, they are currently in breach of the regulations, and it is your duty to inform them and initiate the proper record-keeping procedures.