The latest generation of refrigerants was designed to help to mitigate global warming, but there's an impediment to their widespread use, says Tim Mitchell.
07 May 2019 | Tim Mitchell
The perfect refrigerant would be non-toxic, non-flammable, energy-efficient, and versatile across applications and never leak. It would also have zero global warming potential (GWP) - the amount of heat a greenhouse gas traps in the atmosphere.
But the perfect refrigerant does not exist, so compromise is necessary. Most low-GWP refrigerants are unstable and volatile, which means they will be flammable and often potentially explosive, as with hydrocarbon refrigerants such as propane or isobutane.
The only practical way to have a non-flammable fluid is to accept a higher GWP. But regulations make this difficult.
The challenges of F-gas regulations
The F-gas regulations are legally binding EU rules on the use of fluorinated greenhouse gases (F-gases) such as hydrofluorocarbons (HFCs), including the phasing down of CO2 equivalence of refrigerants in use, and the phase-out and banning of some very high GWP HFCs.
Anyone who makes, uses or services equipment containing F-gases, produces or wholesales F-gas, and imports or exports F-gas, or equipment containing F-gas, to or from the EU, must comply with these rules.
The F-gas regulations are driving us towards ever-lower GWP (and therefore higher flammability) refrigerants.
Shifting time frames
GWP is currently measured on a 100-year base - the number indicates the relative effect of F-gases over the course of 100 years standardised to CO2, which has a GWP of 1.
If we based GWP on 20 years or any other time frame the GWP value would change. Indeed, Greenpeace and other bodies have debated whether there is a case for changing the base number to 20, both to reflect the high short-term damage that HFCs can do and because we don't have 100 years to solve global warming.
Low GWP refrigerants are generally 'mildly' flammable once they get below a value of around 700, moving towards potentially explosive at the very low end. So, as we are driven by the F-gas regulations towards lower GWP, we hit this flammability challenge.
Other regulations limit the currently allowable refrigerant charge sizes to the point where it is impractical to produce big systems with refrigerants carried though pipes in buildings. The alternative is to fit central plant, often in a separate plant room, which can be practicably restrictive.
We need the regulations to protect people and property, but in some ways they conflict with the driver to reduce GWP.
The moment for change
The first upshot is that regulations will have to become more 'joined up', charge sizes adjusted and refrigeration/air conditioning (AC) machinery redesigned.
The second impact is that we will become more comfortable with flammable gases in our environment. But this means the HVAC industry will have to upskill. Leaking refrigerant pipework is already illegal, but rather than resulting in an 'invisible' global warming problem, it is going to become a health and safety issue, which means everybody will have to take it more seriously and be better trained to deal with it.
Flammability is not unheard of in cooling systems. We have 350-plus chillers using propane - a highly flammable refrigerant gas - in a major supermarket chain, and the risks of this are mitigated in design and construction by the professional teams, and in operation by our highly trained personnel and user awareness.
Third, arguably, is that flammability will drive collaboration in the construction process and will force the installation of HVAC equipment to the fore.
So the days of rushing to finish the job will have to end. The right amount of time and planning will have to be allowed for designing and installing, commissioning and testing AC systems. It's no bad thing for the industry that the flammability issue will oblige us to become more professional.
Tim Mitchell is sales director at Klima-Therm