justified if the performance of HFC-245ca has been proven in the laboratory and the
application deemed commercially viable exclusive of the flammability issue.
How difficult will it be to identify cost effective methods of using HFC-245ca as safely as
Class 1 refrigerants? Consider the following: HFC-245ca has no measurable flash point
and will not sustain a flame in dry air at room temperature. However, by ASHRAE 34 and
UL-2182 flammability test conditions, HFC-245ca is expected to carry a Class 2 rating of
"lower flammability". Use of a Class 2 refrigerant according to ASHRAE 15 requires, in
addition to the class 1 requirements, a one-hour fire-resistant rating for the machinery
room and compliance with Class 1 Division 2 of the National Electrical Code. ASHRAE
15 and the NEC call a machinery room with a Class 2 refrigerant a "hazardous location."
Thus, to use HFC-245ca as safely and cost effectively as a Class 1 refrigerant, the
industry must resolve the safety and cost issues associated with ASHRAE 15 and the
marketing issues of dealing with a "hazardous location."
Several studies have indicated that "true risk" does not come in discreet increments but
is rather a continuum. For example, Calm writes "Recognition is growing that all
refrigerants containing hydrogen (including HCFCs and HFCs) are potentially
combustible under some conditions."
4
Dekleva writes: "...as the industry scrutinizes this
parameter (flammability/combustibility) more closely (especially in light of the new
refrigerants), the absolute measure of reactive and non-reactive (flammable and non-
flammable/combustible) becomes smeared."
5
Thus, the potential Class 2 rating for
HFC-245ca may be overstating the real risk associated with its use, but that may be
sufficient to prevent its commercialization. Continued assessment of the risks associated
with the use of marginally flammable refrigerants such as HFC-245ca is desirable along
with a review of the technical requirements for classification of refrigerants.
Theoretical Performance
Many of the low pressure chillers produced today and in the past have contained 3
stages of compression plus economizers between stages, so an analysis of the
theoretical performance of HFC-245ca in this class of equipment is appropriate.
Single and three stage refrigeration cycles are illustrated on temperature-enthalpy
diagrams in Figures 1 and 2 respectively. The processes portrayed in Figure 1 are
typically described as shown in Table 3.
Table 3. Single Stage Process
4
Calm, J.M. "Refrigerant Safety" ASHRAE Journal, July 1994. p. 22
5
Dekleva, T.W., Lindley, A.A., Powell, P. "Flammability and reactivity of select HFCs and mixtures"
ASHRAE Journal, December, 1993.
4
Process Line Process Process Line Process
1 - 2' Isentropic Compression 1 - 2 Adiabatic Compression
2 - 3 Desuperheating 3 - 4 Condensing
4 - 5 Adiabatic Expansion 5 - 1 Evaporation
6 - 7 Condenser Water Temp 9 - 8 Evaporator Water Temp