2.5.2 Categories
As defined by the EN 378, the following Occupancy categories require attention to the
allowable charge and the provisions for each individual category.
Occupancy types as defined under EN 378 Standard are:
(A) – Rooms, parts of buildings or buildings where people may sleep, people are
restricted in their movements or an uncontrolled number of people are present or to
which any person has access without being personally acquainted with the necessary
safety precautions.
(B) – Rooms, parts of buildings, buildings where only a limited number of people may be
assembled, some being necessarily acquainted with the general safety precautions of the
establishment.
(C) –Rooms, parts of buildings, buildings where only authorized persons have access,
who are acquainted with general and special safety precautions of the establishment and
where manufacturing, processing or storage of material or products take place.
Where there is the possibility of more than one category of occupancy, the more
stringent requirements apply. If occupancies are isolated, e.g. by sealed partitions, floors
and ceilings, in which case the requirements of the individual category of occupancy
apply.
NOTE: Attention is drawn to the safety of adjacent premises and
occupants in areas adjacent to a refrigerating system. Refrigerants
heavier than air can cause oxygen deficient pockets at lower levels.
2.5.3 Construction
If the charge is more than .15 kg (0.33 lb), then a sudden loss of refrigerant should not
raise the mean concentration in the room above the practical limit 0.008 kg/m
(0.0004994 lb/ft). The room volume governs the total charge size. This can be
determined by the equation 2.5.3.a.
M
r
= 0.2 · (LFL) · V
room
(Equation 2.5.3.a)
Where:
M
r
= maximum allowable refrigerant charge per separate refrigerant circuit (kg or lb)
V
room
= room volume (m
3
or ft)
LFL = lower flammability limit of refrigerant (kg/m
3
or lb/ft) from table 2.3
Similarly, the minimum room volume for a specific refrigerant charge is determined by
the equation 2.5.3.b.
V
room =
(Equation 2.5.3.b)
M
r
0.2 · (LFL)
In practical terms, for a 100m (3531 ft) of room volume, the maximum allowable
charge would be 760 g (27 oz) of Duracool 22a® per refrigerant circuit. Charges in
systems below ground (i.e. cellars and basements) are restricted to a maximum of 1.0 kg
(2.2 lb) even with larger room sizes. Sealed systems containing a charge of less than
150 g (5.3 oz) can be situated in any location, regardless of room volume.
Note that all charge limits apply per single refrigerant circuit, on the basis of probability
that two circuits will not have catastrophic failures simultaneously.
Duracool Refrigerants Inc. 12
