Safe and practical applications: natural refrigerants

The higher flammability of low-GWP refrigerants in heat pumps and air conditioning systems has to be carefully considered by designers and installers. Alex Smith reports

Viessmann’s Vitocal 150-A/151-A propane heat pump

New F-gas regulations and a focus on cutting embodied carbon in HVAC systems mean that reducing the impact of refrigerants on the environment has become a key concern for engineers. To reflect this, CIBSE is asking entrants to its Building Performance Awards to provide information on the global warming potential (GWP) of the refrigerant in their projects and its in-use leakage rate.

F-gases in refrigerants are known contributors to global warming, and the EU F-gas Regulation 2024/573, which came into force on 11 March, aims to further curb the use of refrigerants with high GWP. The regulation mandates that, from 2027, chiller, air conditioning and heat pump systems under 12kW must have GWP limits of 150, and, by 2032, there will be a full F-gas ban in these systems. From 2027, larger split systems and chillers must have a GWP below 750.

This is part of wider plans to end the use of F-gas, with the EU parliament voting in January to phase-out HFCs, which make up 90% of F-gases, by 2050. This will be enforced by the reduction in HFC quotas set out in the revision of F-Gas III (EU) 517/2014. From 2025, the quotas allocated for HFCs by the European Commission will lead to a reduction of 22% compared with 2024, rising to 12% from 2036. This will result in price rises for remaining refrigerant, which the EU hopes will incentivise a move to low-GWP systems.

The UK is currently drafting its own legislation to align with these rules. It is expected to publish a stakeholders’ consultation document this summer, with a draft regulation published in the autumn.

The Net Zero Carbon Buildings Standard (NZCBS), due in the autumn, will also place limits on the GWP of refrigerants used. A consultation proposed a maximum GWP of 675, which is the GWP of R32, a common refrigerant. It also proposes that refrigerants be accounted for within embodied carbon calculations.

The regulations are driving demand for systems using natural refrigerants, such as ammonia, propane and carbon dioxide, which have near-zero GWP. This is the experience of Edoardo de Pantz, managing director at Acquaria, which manufactures propane (R290) heat pumps and chillers. ‘The market is running faster than the regulations are. The whole supply chain is asking for near-zero GWP heat pumps,’ he says.

There’s no point having the exemption if you can’t get the equipment because the quota for these refrigerants is reducing so quickly

BESA technical director and Institute of Refrigeration president Graeme Fox says the upcoming ban on high-GWP refrigerants has led to a sharp uptick in propane systems.

Propane has higher flammability than higher-GWP refrigerants, with an A3 safety classing, and Fox says installers will need to upskill to work safely with the refrigerant.

The EU F-gas regulations state that installers will need a refresher course within five years of the implementation date of the latest regulations (April 2029), and every seven years thereafter. But Fox notes that small systems with a GWP of more than 150 will be banned within three years – before the date when installers have to complete the course. He says manufacturers may stop supplying higher-GWP equipment, even before the implementation date

‘Technicians could be installing highly flammable refrigerants before they’ve had the necessary training, which is very much a concern to the industry,’ says Fox.

In response to the lack of awareness around propane, BESA has published a technical bulletin on R290 in air conditioning equipment and its practical application. Fox says R290 air-to-water monobloc heat pumps designed for housing need special consideration. The refrigerant’s flammability means it must be more than 1.5 metres from an openable window or door, according to manufacturers, says Fox, and because it is heavier than air, it must be more than 1.5m from air bricks and downpipes, to prevent leaking propane from infiltrating the house.

‘In most houses, you’re going to really struggle to get anywhere near the outside of that house and avoid an air brick by 1.5 metres either side of the unit,’ says Fox.

There are also implications for the retrofit of split air conditioning heat pumps in retail outlets or office applications, he adds. A typical application in these sectors is a grid of R407c condensers placed about 300mm apart, perhaps on a gable end. Currently, if one unit fails it can be replaced a similar unit, which is fairly straightforward.

However, it would be impossible to swap in a propane unit, because older units use A1-rated refrigerant that does not require Atex-rated electrical equipment, such as fan motors and electrical meters, so the neighbouring unit is a potential ignition source. (Atex is the name given to the two European directives for controlling explosive atmospheres.) ‘There are very serious implications for retrofit and retrospective repair work with the location of these new units,’ says Fox.

The issue can no longer be left to the AC contractor, he adds, because – under the Building Safety Act – the principal designer has to take responsibility: ‘They have to be aware of it.’

Currently, the European standard BS EN378 governs the safety and environmental standards of air conditioning, refrigeration, chillers, and heat pump systems, and this can be used with three EN60335 product standards that provide more specification details. Several CIBSE guides refer to BS EN378, including AM17 and Commissioning Code R, Guide B and Guide B3. A new version of the European standard is expected later this year (see page 13 to find out more about EN378).

An area Fox believes the EU has overlooked is the application of systems in airports, railway stations and military bases, where flammable A3 refrigerants cannot be used because of the danger of ignition – via sparks from trains and tracks, for example.

‘The EU has a line in the regulations that says higher-GWP refrigerants, such as 410a, can be used if safety standards don’t allow A3 refrigerants, but there’s no point having the exemption if you can’t get the equipment because the quota for these refrigerants is reducing so quickly,’ he says. ‘There needs to be a mechanism to bypass the quota and supply that equipment in these locations.’

For propane chillers, Fox says that – in addition to leak detection and good ventilation – the designer would have to ensure that fans, leak detectors, lights, switches and any power points are Atex-rated.

Chillers and propane

According to De Pantz, three key guidelines are followed to ensure Euroklimat chillers (a partner of Acquaria) are safe: containment of the substance; avoidance of ignition sources; and use of a leak detector.

Most importantly for designers, installers and consultants is that they are aware of the safety standards around handling propane, and that they adhere to these. ‘This is how we can supply the market with propane heat pumps that offer the same peace of mind that we have when commissioning gas boilers in homes,’ he adds.

Every unit is supplied with a standalone gas-detection sensor. ‘To make it a viable fuel option, we, as manufacturers, need to build a heat pump with all the safety measures included to catch any leakage,’ says De Pantz.

Other precautions to avoid the risk of possible ignition sources include moving the compressor’s electronic protection module (Kriwan) into the electrical panel, and ensuring pressure switches are Atex-certified.

He is hopeful that issues identified with the latest F-gas regulation will be fed back into the UK’s upcoming consultation document.

‘Just because something is technically feasible doesn’t mean it’s practically applicable,’ he says. ‘We have to be aware of the nuanced application issues that engineers have on the ground.’