Sooner or later, most workers handling equipment using refrigerants need to deal with flammability. This is one of the main challenges resulting from the global phase down of refrigerants with high global warming potential, since most of the alternatives with acceptable performance are flammable. R-290 (propane), R-32, R-454B or R-1234yf are some examples of flammable refrigerants that are widely used in refrigeration, air conditioning and heat pump applications (RACHP).

As we know, dilution in air is a simple solution to minimise the unwanted effects of flammable or toxic material release. In the case of flammable substances, the aim of dilution is to decrease the concentration of the fluid to a level below the lower flammability limit (LFL). 

The safety standards that are commonly used in RACHP include several different ventilation methods to dilute flammable refrigerants. The aim of this post is to analyse the different ventilation options that are included in the following European standards:

• EN 378: general standard for refrigerating systems and heat pumps 
• EN 60335-2-89: particular requirements for commercial refrigerating appliances and ice-makers with an incorporated or remote refrigerant unit or motor-compressor
• EN 60335-2-40: particular requirements for electrical heat pumps, air-conditioners and dehumidifiers

It should be highlighted that the information reported in this post refers to the international version of EN 60335-2-40, IEC 60335-2-40, as the latest edition of the latter (7.0) has not yet been harmonised in Europe. In any case, European product standards are generally harmonised without significant modifications with respect to the international versions, and thus the same is expected in this case.

Continuous ventilation or activated by a leakage detection system?

Generally, the ventilation options included in RACHP standards can be continuous or activated by a leakage detection system (excepting natural ventilation, obviously). The procedures described in IEC 60335-2-40 for each case are as follows:

• Continuous mode: the mechanical ventilation system shall run continuously, other than for short periods for maintenance and service. The airflow shall be monitored continuously and, within 10 seconds in the event that the airflow is reduced below the minimum required volume flow of the ventilation, the user shall be warned that airflow is reduced and compressor operation shall be disabled.
• Leakage detection system: when the leakage detection system is activated, the mechanical ventilation system of the appliance to deliver indoor airflow shall be energised at or above the minimum airflow and compressor operation shall be disabled. This shall continue for at least 5 min after the leakage detection system has reset.

In both cases, compressor operation shall not be disabled if it reduces the leakage rate or the total amount released into the indoor space. 

Mechanical ventilation: enclosure or room

Mechanical ventilation is one of the methods proposed in IEC 60335-2-40 and EN 378 to dilute leaked refrigerant. It can be incorporated inside the appliance enclosure or in the room where the appliance is located.

The advantage of using mechanical ventilation when applying the requirements of IEC 60335-2-40 is that the refrigerant charge in an indoor space can be increased up to the maximum permitted by the standard. For instance, having a mechanical ventilation system means up to 5 kg of propane and 80 kg of R-32 can be used without any restrictions in the room area.

The requirements for an appliance enclosure specified in IEC 60335-2-40 include the fact that the refrigerating circuit shall be provided with a separate enclosure that does not allow any flow from inside the enclosure to the room. To do that, the appliance enclosure shall have a ventilation system that produces airflow from the inside of the appliance to the outside through an exhaust ventilation duct.  

A ventilation enclosure is also among the possibilities described in EN 378. In particular, it allows a class IV location, which means that the refrigerant charge can be increased up to 130 x LFL x 1.5 for A2L and A3 refrigerants. This, for instance, gives as a result 7.4 kg of R-290 or 60 kg of R-32.

The definition included in EN 378-1 for ventilated enclosures is practically the same described in EN 60335-2-40. EN 378-1 defines it as an enclosure containing the refrigerating system that does not enable air to flow from the enclosure to the surrounding space and has a ventilation system that produces airflow from the enclosure to the open air through a ventilation duct.

According to EN 378-2, if the ventilation enclosure is activated by a sensor, the ventilation system shall be activated before 25 % of the LFL is reached, a failure shall be indicated and the system shall be switched to safe mode with the fan switched on until the failure has been resolved. The ventilation system can also operate in continuous mode.

Machinery rooms as defined by IEC 60335-2-40 shall meet the requirements of ISO 5149-3:2014, Clause 5 and ISO 5149-3:2014/AMD1:2021, 5.12, 5.14 and 5.15. ISO 5149 is the international standard that EN 378 is based on.

EN 378-3 specifies that the ventilation of machinery rooms shall be sufficient both for normal operating conditions and emergencies. Requirements include that the air shall be vented outdoors whereas mechanical ventilation shall be independent from other ventilation systems and re-circulation of air into the room shall be avoided. 

Ventilation for normal operating conditions shall be in accordance with national regulations with a minimum of 4 air changes per hour when the machinery room is occupied. In the event where ventilation cannot be achieved, an audible and/or visual alarm shall be activated and power supplies shall be terminated. 

For emergency mechanical ventilation, if gas detection is required in the machinery room, the emergency mechanical ventilation system shall be activated by a detector located in the machinery room. Emergency mechanical ventilation shall be provided with two independent emergency controls, one located outside the machinery room, and the other inside.

EN 378-3 also specifies that machinery rooms for flammable refrigerants shall be assessed with regard to refrigerant flammability and classified according to the requirements of EN 60079-10-1 for the hazardous zone.

Natural ventilation, only for A2L refrigerants 

IEC 60335-2-40 offers the possibility of using natural ventilation as an alternative to mechanical ventilation only for A2L refrigerants. In doing so, the charge of A2L refrigerants can be increased up to the maximum permitted by the standard without any restriction in the room’s area. This means, for instance, a refrigerant charge up to 80 kg of R-32. 

There are two options: natural ventilation to outdoors or to indoors. Natural ventilation from an occupied space shall not be made to outdoors because the user can block the natural ventilation to the outside if it is cold outside. It should also be taken into account that natural ventilation to outdoors is not allowed below ground level. 

Integral circulation air flow

Integral circulation air flow is a method that allows the refrigerant charge of flammable refrigerants to be increased in accordance with IEC 60335-2-40, but to never more than 26 x LFL for A2 and A3 refrigerants (1 kg of R-290) or 52 x LFL for A2L (16 kg of R-32), or the minimum area of the room where the appliance can be located to be reduced, for a given refrigerant charge. It involves a fan integrated into the appliance. The requirements for A2L refrigerants (established in Edition 6 of the standard) are different with respect to those for A2 and A3 (new in Edition 7).

EN 60335-2-89 mentions airflow as a possibility, presumably referring to a method that can be used to dilute the refrigerant when it is necessary to pass one or more of the required leakage tests. As also required in IEC 60335-2-40, the airflow shall be produced by components that are part of the appliance. 

Moreover, EN 378-2 specifies ventilation as a method for components and apparatuses that are considered to be a source of ignition. In particular, if such components and apparatuses are ventilated with a sufficiently high airflow (either permanently or initiated prior to energising them), they are not considered to be a source of ignition and application of the standard EN 60079-10-1 is not required to assess their risks.

Air duct system to one or more rooms

Air duct system is a method that was introduced in Edition 6 of IEC 60335-2-40 for A2L refrigerants. It allows the refrigerant charge to be increased to a maximum of 260 x LFL in some cases (80 kg of R-32) or the minimum area of the room where the appliance can be located to be reduced, for a given refrigerant charge. One of the requirements is that the supply and return air are directly ducted into the space.

Considerations

For the sake of simplicity, some details of the different ventilation methods have not been included, for example the formulas to calculate the minimum airflow for mechanical ventilation or the minimum opening for natural ventilation. Therefore, the information contained in this post must be completed with other details specified in the standards, whereas the scope of the text is to give an overview of the different ventilation options for the dilution of flammable refrigerants. Minimising the risks associated with the use of flammable refrigerants must be a priority and one of the most suitable methods is dilution by ventilation.

If you are interested in learning more about this topic, download our new “Flammable refrigerants” white paper!

Download the white paper

Related Posts

EN 378: which cases does it apply to?

The cost of 500 grams of propane

Pros and cons of A2L refrigerants in heat pumps and air conditioners

How is ATEX intertwined with HVAC/R?