Refrigeration safety devices
Automatic Operation of Refrigeration Equipment

Pressure relief valves intervene in the event of dangerous condensation pressure, either by releasing the refrigerant into the open air, or even out of the building, if it is likely to be a hazard to neighbors (which is essential with ammonia, which is toxic), or by returning it to the low-pressure circuit; in this case, the circuit must be fitted with a pressure relief valve, releasing into the open air. Pressure relief valves can be relief valves, rupture discs or fuses.

The relief...