NH3 refrigeration installations and explosion safety

Did you know that, under standard safety regulations, the machine room of an ammonia refrigeration installation would typically have to be classified as zone 2 because of the risk of explosive atmospheres? Interestingly, the EN 378-3 standard allows us to deviate from the requirements of this zoning, provided certain conditions are met.

According to EN 378-3, the electrical equipment of an ammonia refrigeration installation does not have to meet the requirements for hazardous areas if proactive safety measures are implemented. One of the crucial measures is switching off all non-ATEX-rated equipment in the event of an ammonia leak that leads to dangerous concentration levels. This means that in the event of an incident, the risk of igniting an explosive atmosphere is avoided, because the devices that can generate sparks or heat and could therefore cause an explosion have already been switched off.

This equipment must be switched off from outside the machine room to guarantee the safety of personnel and to minimise the risk of ignition in a potentially hazardous environment. This approach ensures that, although zone 2 conditions may technically be present, we do not need to apply the full requirements of ATEX zoning, which can save cost and complexity while safety remains guaranteed.

So thanks to EN 378-3, through precautionary measures such as switching off non-ATEX equipment, we can effectively avoid the requirement for a full ATEX design of the machine rooms of ammonia refrigeration installations.