Playing it cool17 October 2018

Global warming is a clear and present danger to the planet, but there are ways for engineers to help reduce its impact. Ian Vallely explains

In an ideal world, everyone who needs to use a refrigerant would use the same type. It would be non-toxic and non-flammable; it would be versatile enough to work across any application and cope with any pressure; it would not leak and it would offer outstanding energy efficiency; it would not deplete the ozone layer and it would have a low global warming potential (GWP).

Unfortunately, there is no such thing as a perfect refrigerant. Reducing the impact on global warming by using a low-GWP gas almost certainly means the refrigerant will become flammable (although this flammability is low compared with a hydrocarbon, such as propane or butane).

The only way to have a non-flammable fluid is to accept a higher GWP. However, this is unacceptable under the latest regulations. So selecting the right refrigerant for a particular application inevitably becomes a compromise.

This, though, begs a fundamental question – which is the single most important characteristic of refrigerant gas? Over the last decade or so, the focus has been on reducing the GWP, a relative measure of how much heat that specific greenhouse gases trap in the atmosphere. This is standardised to carbon dioxide (CO2), which has a GWP value of one.

Fluorinated (or F) gases are man-made gases used in a range of industrial applications including refrigeration and fire protection. There are three groups: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). F-gases are particularly ferocious greenhouse gases with GWPs in the range 1,500-4,000 (that is 1,500-4,000 times more damaging than CO2). As a result, efforts to regulate them have grown over recent years.

A quota-based system

The original F-Gas Regulation, released in 2007, EC 842/2006, was designed to reduce emissions from F-gases, but it really only involved factors such as leak testing, monitoring and servicing of systems. Essentially, the only ban it brought in was to say that automotive air conditioning would have to move to a refrigerant with a GWP of less than 150 for new models by 2012 and for all cars from 2017.

The second F-Gas Regulation (EU 517/2014), which came into force in 2015, was different. It introduced a phase-down mechanism involving a gradually declining cap on the total placement of bulk HFCs on the market in the European Union.

F-Gas Regulation 2015 set out caps and phase-down schedules for the sale of F-gases. So, in 2015 there was a starting point volume allocated to companies that had placed F-gases on the market between 2009 and 2012. They were given a proportion of the ‘quota’ of gases allowed based on sales.

Martyn Cooper, commercial manager of the Federation of Environmental Trade Associations (FETA), explains that this quota is granted in CO2 equivalent tonnes, which iscalculated by multiplying the mass in tonnes of the F-gas by the associated GWP. He adds: “It’s not actual tonnes, and this means the amount of product sold is reliant on the GWP of the refrigerant.

“So 2015 was the baseline. In 2016 and 2017 respectively there was a 7% reduction. However, the big reduction has come this year, with a 37% reduction in quota.”

By 2030, only 21% of the current amount of HFC refrigerants now used by the industry will remain in circulation. As a result of these manoeuvrings over F-gas quotas, UK refrigerant suppliers dramatically hiked medium-to-high GWP refrigerant prices, with the highest GWP gases now double the cost they were in 2016.

Says Graeme Fox, the head of Refcom, which operates the industry’s mandatory F-gas certification scheme: “Users of R404A refrigerant (and another high GWP refrigerant called R507), for example, were confronted with a 60% price rise in a single month last year and the price of medium GWP gases like R410A also continues to rise sharply.”

R404A has a GWP of 3,922 and, along with every other refrigerant with a GWP above 2,500, will be banned in new stationary refrigeration equipment from 2020, including for service and maintenance purposes. FETA’s Cooper explains: “That effectively wipes out R404A, which is the most commonly-used refrigerant in commercial refrigeration.”

However, as a general rule, as the GWP of a refrigerant (or refrigerant blend) falls below about 1,000, these products start to exhibit flammability, albeit low.

Cooper again: “This is a feature the industry will have to embrace, as there are no non-flammable low GWP options. For most refrigerants, GWP and flammability are inversely related. Lowering the GWP means that the substance is less stable and flammability tends to increase.”

Hazardous materials

There are safety standards in place which lay down maximum refrigerant charge sizes for different applications, room sizes and capacities. For example, BS EN378 is a safety and environmental standard designed to prevent the formation of a flammable atmosphere. It provides guidance for companies that design, construct, install, operate, maintain and use vapour compression systems for refrigeration, air conditioning, heat pumps, chillers and other similar systems.

All refrigerants also come under the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) which, in themselves, are the UK’s interpretation of the European ATEX Directives.

As FETA’s Cooper points out: “Basically, all refrigerants are classified under DSEAR as hazardous, even the non-flammable ones, because they are pressurised gases... If these products are handled, installed, serviced and maintained properly there should be no problem at all. It’s all about risk assessment. This is a critical area [but it] doesn’t need to be too onerous. I suspect that plant and industrial engineers will be doing risk assessments as a matter of course anyway.”

Nonetheless, the Air Conditioning and Refrigeration Industry Board, the Institute of Refrigeration and FETA can point plant engineers in the right direction for training should this be required.

BOX OUT 1: F-gas safety qualifications

Plant engineers in charge of the day-to-day operation of equipment containing F gases need different qualifications for:

● Stationary refrigeration and air conditioning or fire protection systems

● Mobile air conditioning

● Electrical switchgear

● Solvent recovery

They must have a personal qualification certificate as an individual even if they work for someone else. If they are a business that works on third party systems or equipment, their engineers must also have personal qualifications as well as a company F Gas Certificate. The same applies if they are a sole trader (see

BOX OUT 2: Alternative refrigerants

A number of alternatives offering a lower global warming potential (GWP) are available to retrofit existing R404A equipment. These include R448A and R449A, which both have a GWP of around 1,300.

There are also long-established alternative fluids for some applications including hydrocarbons, ammonia and CO2, but these require engineers to deal with limitations on charge volumes, some toxicity, flammability or higher working pressures.

There is, however, no known non-flammable alternative for R410A refrigerant. As a result, contractors need the right training and must also make sure they are using the appropriate recovery equipment to deal with flammable and toxic substances.

Refcom’s Graeme Fox says: “Sticking with the lowest GWP refrigerants is still an option for now, and R32 is being widely used in small ‘split’ air conditioning systems. It is one of the ingredients that make up R410A, but has a GWP of just 675 (around a third of R410A) and has higher volumetric capacity, which means system charges can be reduced to further help meet tightening HFC quotas.”

But new types of refrigerant – hydrofluoroolefins (HFOs) – are also gaining traction. These are thermally stable and have a very short atmospheric life.

A feature of many of these products (and some existing refrigerants such as R32 and ammonia) is that they exhibit low flammability, and hence a new classification has been introduced to cover this feature – A2L – indicating ‘low flammable’ gases.

Low flammable refrigerants are very difficult to burn. R32 and HFO refrigerants, for example, can be ignited with a bare flame, but as soon as the flame is taken away, the fire goes out. The flame doesn’t propagate in a way that it would with a hydrocarbon such as propane or butane.

“However”, warns Fox, “HFOs are not suitable as ‘drop-in’ replacements, so anyone designing a system today that might need to use traditional HFC gas should consider the cost implication of that system quickly having to be ripped out and completely replaced.”

Adam Offord

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