Hermetically sealed and semi-hermetic compressor classification as no higher than category I as defined by PED and falling in the scope of other EU-directives e.g. for low voltage or machinery, are excluded from the scope of PED. This applies to hermetic and semi-hermetic compressors no higher than category I.
The exclusion in PED article 1 paragraph 2 (j) is not applicable to hermetic compressors because pressure is a significant design factor since their external envelope has as its principal function to ensure that the refrigerant is confined.
For semi-hermetic compressors which include moving parts and for which the external envelope is primarily designed for mechanical loads (speed and vibration), thermal load (to limit the possible deformation due to temperature), stiffness of the structure (external mechanical loads and weight of the equipment), an exclusion based on PED article 1 paragraph 2 (j) is to be assessed on a case by case basis.
Classification of hermetically sealed compressors
Hermetically sealed refrigeration compressors are pressure vessels.
Usually, a compressor is composed of two chambers: the low pressure side PS1, the volume of which is V1, and the high pressure side PS2, the volume of which is V2. The equalizing pressure during standstill is PS3 (always higher than PS1).
The category is the higher of the low pressure side (based on PS3 and V1) and of the high pressure side (based on PS2 and V2).
Note 1: The highest pressure cannot occur simultaneously on both sides; during standstill there is no direct communication between the 2 chambers, due to the presence of the valves; if a valve fails, the movement of the piston cannot create pressure.
Note 2: When a compressor has more than 2 chambers (i.e. several chambers constitute the low pressure side and several chambers constitute the high pressure side) the above volumes V1 and V2 are the sums of the low pressure and the high pressure chambers respectively.
Note 3: In application of the definition of “volume” given in PED article 2 paragraph 10, the volume of the mechanical parts is to be excluded from the volume to be taken into account but not the volume of the oil contained.
