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Using low to medium GWP refrigerants

Fire

By Barney Richardson

Refrigeration equipment and air-conditioning units using low to medium global warming potential (GWP) refrigerants, such as R290 which is a propane or R600a, an iso-butane and HFC-32 a methylene fluoride refrigerant are becoming more common. 

The refrigeration and air conditioning market in South Africa is changing and this is globally driven in response to ozone depletion and climate change with global warming due in part to HCFC and HFC refrigerant leakages.

There is also the demand for greater energy efficiency in equipment. Service practitioners and installers need to have the new and necessary skills for the safe handling of all refrigerants, particularly flammable refrigerants.

It is very important for service practitioners and installers to have updated skills in the handling the new alternative refrigerants that are coming into the marketplace. Good servicing practices are recognised as the best approach to doing the job right. This is particularly needed for domestic and small commercial refrigeration where Hydrocarbon refrigerants are already being used.

SARACCA is a member, representing South Africa, of U-3ARC. (Union of Associations of African Actors in Refrigeration and Air-Conditioning) This is an association promoting refrigeration standards and skills throughout Africa. They have sent to me a handbook for Good Servicing Practices for Flammable Refrigerants, produced by the United Nations Environment Programme. The aim of this guidebook is to provide Refrigeration and Air Conditioning practitioners with the up-to-date skills and key safety classifications required for flammable refrigerants.

“The auto-ignition temperature is the lowest temperature at which a refrigerant will

While South Africa does not have room air conditioners using flammable refrigerants as yet, there are many domestic and small commercial refrigerators and beverage coolers using these refrigerants. It is important safety guidance for the installation and servicing of refrigeration appliances and equipment designed to use flammable refrigerants such as R290 and R600a.

All flammable refrigerants must be handled with caution, precautions and in accordance with national regulations, the manufacturers’ user and operation manuals and safety standards. The manufacturers’ refrigerant charge limits must always be considered and be complied with when servicing a unit.

Important terminology to be aware of are the lower flammability limit (LFL). This is the minimum concentration a substance, in this case refrigerant, that is capable of propagating a flame through a mixture of the substance and air under specified test conditions.


Graphic 1: The fire triangle. Image credit: Creative Commons | Wikimedia


 The upper flammability limit (UFL) is the maximum concentration of the refrigerant that is capable of propagating a flame. ASHRAE term is the refrigerant concentration limit (RCL); this is the refrigerant concentration limit, in air, determined and intended to reduce the risks of acute toxicity, asphyxiation, flammability and fire hazards in normally occupied, enclosed spaces.

The auto-ignition temperature is the lowest temperature at which a refrigerant will spontaneously ignite in a normal atmosphere without an external source of ignition flame or spark. This is the biggest danger. Since a flame can be propagated in the range between the LFL-UFL, a practitioner should avoid the concentration of refrigerant in the working area reaching the LFL and the temperature of refrigerant from reaching the auto-ignition temperature.

Full safety checks must be carried out and procedures be followed at all times and for all refrigerants, even when they are classified as lower toxicity or non-flammable. To prevent fire hazards when using flammable refrigerants, relevant standards have been adopted to limit the charge size of flammable refrigerant in refrigeration and air conditioning units.

The fire triangle is composed of the three components that produce a physicochemical reaction to ignite a fire: heat, fuel, and oxygen. A fire can occur naturally when these three elements occur simultaneously in the appropriate proportions. This is what happens when a practitioner does not follow procedures and precautions when working with flammable refrigerants.

In principle, the following factors must be considered to determine charge limits of flammable refrigerants in a RAC system. Flammability group of the refrigerant, for example, R-290 and R600a are group A3 (flammable) while R-32 is group A2L (lower flammability). The A designated lower toxicity. Occupancy classification and location classification of refrigeration and air conditioning equipment must also be considered.

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