CPD PROGRAMME | LOW-GWP REFRIGERANTS widespread adoption of R32 (and blended refrigerants such as R454B) in high-pressure applications that formerly employed R410A. There are numerous considerations to assess a potential refrigerant for operation at appropriate evaporating and condensing temperatures (as discussed in IoR Guidance Note 373) not least the refrigerant density, operating pressures, thermodynamic properties and the resulting system energy performance, alongside safety in application, operation and reuse/disposal. Gluckman notes in his recent webinar4 that the swift changes in refrigerant application following the introduction of the F-gas regulation were built on many years of research and development, which began well before the regulation came into being. The IEA report1 contends that even with todays F-gas refrigerants and current rates of leakage, heat pumps still reduce greenhouse gas emissions by at least 20% compared with a high-efficiency gas boiler, even when running on emissions-intensive electricity. In regions accounting for 70% of world energy consumption, the resulting emissions savings are above 45%, and reach 80% in countries with cleaner electricity mixes. By employing alternative refrigerants, as discussed later in this article, IEA considers that these values can be improved by a further 10%. The swiftly changing energy marketplace and the reinvigorated awareness of the impacts of climate change have accelerated the demand for the UK and the EU to undertake a review of the F-gas regulations. In April 2022, the EU set out a first set of proposals with an ambitious timetable of becoming EU law in 2023 (these will likely also influence the UK deliberations on legislation that is scheduled to come into force in 2024-25). The proposals reinforce and extend the leakage, recharging, and refrigerant recovery provisions of the 2014 regulations but, most significantly, accelerate the phase-down schedule for HFCs to the timetable illustrated in Figure 1. The headline proposals to accelerate the reduction in the availability of HFCs, as summarised in Table 1, have solicited both strong positive and negative opinions on the impact of a speedier reduction of HFCs. To achieve GWP<150 in splits and heat pumps smaller than 12kW means potentially using a hydrocarbon (such as propane, R290); blended refrigerants such as R454C and R455A; pure HFOs such as HFO-1234yf or HFO-1234z; or a new, yet to be marketed refrigerant. As noted in the recent IEA report,1 switching to non-HFC refrigerants is technically possible, but there are risks impeding deployment, owing to the technical 62 February 2023 www.cibsejournal.com Figure 1: Proposed HFC phase-down compared with current F-gas provisions (Source: Ray Gluckman4) 97.5% final cut in 2048 95% cut in 2030 2014 F-gas phase-down schedule 90% cut in 2027 Application Proposed F-gas phase-down schedule Limiting GWP Implementation year Any self-contained* refrigeration equipment 150 2025 Plug-in* and other self-contained air conditioning and heat pump equipment 150 2025 Less than 12kW 150 2027 More than 12kW 750 2027 Split air conditioning and heat pumps Table 1: Proposed changes to F-gas regulation (published April 20224) *Interpretation of terminology still to be clarified and cost implications, particularly as refrigerants cannot be simply swapped into existing units. To meet the current and future F-gas requirements, some safety challenges will need to be overcome. As F-gas registration scheme operator REFCOM5 points out: The downside to lowering the GWP of a gas tends to be the increasing flammability or related issues. All flammable refrigerants (with flammability classification of 2L, 2 or 3 see Table 2) will not ignite if the refrigerant concentration in room air stays below the lower flammability limit (LFL). BS EN 378 Refrigerating systems and heat pumps safety and environmental requirements sets limiting refrigeration concentrations that are deemed safe for applications in buildings. The standard relates the size of an occupied space with the amount of refrigerant (contained in pipework, fittings and components) allowed within that space, and also sets requirements for any leak detection devices. Many of the replacements for the legacy HFCs are mildly flammable and are classified as 2L they are hard to ignite, and have a slow burning velocity, are considered to be safe for use in approved systems, and can be considered safe for general handling with appropriate practices and, importantly, with properly skilled operatives. BS EN 378 restricts the amount of A2L refrigerants that can be used in occupied spaces, as well as requiring leak detection systems, and this can make the application of the lower-GWP A2L refrigerants for example, R32 more complex in applications such as variable refrigerant flow (VRF) or split systems serving applications such as hotels and offices. An increasingly common way to obviate the need for safety constraints (as standardised by BS EN 378) while providing effective controllable systems, is to utilise a hybrid VRF approach, where the refrigerant is used between the outdoor unit and a hybrid branch controller box (often located in a restricted access area), with water then being used as the medium for transferring cooling or heating into the occupied spaces, as illustrated in Figure 2. Not only does such a hybrid VRF remove the need for leak detection, but it also uses significantly less refrigerant than a traditional VRF system. As a result, the overall carbon footprint of the equipment is reduced, and ongoing maintenance costs (including replacement of refrigerant) are also reduced. A review of the European standard EN 378 is currently under way. It is thought that changes will include new refrigerant charge limits that should allow a wider