ASHRAE Journal - October 2022 - 54

TECHNICAL FEATURE
showed that the most common leak location identified
by service technicians was at the Schrader valves used
for servicing the equipment.
Overall, the refrigerant emissions rates calculated for
the school district were on the lower end of refrigerant
emissions rates assumptions reported in literature, and
R-410A equipment had a lower emissions rate than R-22,
even though R-410A equipment operates at significantly
higher maximum absolute pressures (i.e., approximately
3.0 MPa [435 psi] for R-410A versus 1.8 MPa
[261 psi] for R-22). However, both of these operating
pressures are significantly higher than ambient pressure
of approximately 0.1 MPa (14.5 psi), such that any
hole or failure of the refrigerant line would be expected
to leak significantly regardless of refrigerant type. The
most likely explanation for the result calculated at the
school district is that older equipment is more likely to
leak refrigerant than newer equipment, since the R-22
equipment analyzed was, on average, 11 years older than
the R-410A equipment.
Interestingly, the service port used to check refrigerant
pressures was identified in the service ticket database
as the most frequent leak location, which was primarily
reported in R-22 equipment. Service ports in air-conditioning
systems are generally Schrader valves. It is possible
that Schrader valves are prone to leaks as they age.
Design changes to service ports for refrigeration systems
may reduce overall refrigerant emissions. For example,
a hard-shutoff ball valve could be installed prior to the
Schrader valve as a fail-safe to prevent refrigerant leaks.
Only emissions during the lifetime for operation and
servicing were analyzed, and end-of-life emissions at the
time HVAC equipment is removed were not included.
Because the described approach to maintenance and
operations of HVAC equipment generally only results
in leak detection in response to a comfort complaint,
it is expected that at the time of equipment removal
the average remaining system charge will be less than
the initial charge. This is generally accounted for in an
additional end-of-life emissions factor, which was not
studied here.
A limitation of this study is that data collected was from
one school district in California. The study presents a
method for analyzing leakage rates and motivates investigation
of other data sets (by independent researchers and/
or facility managers) to determine if the findings, including
higher leak rates in older R-22 equipment and leakage
54
ASHRAE JOURNAL ashrae.o rg O CTO B E R 2022
TABLE 6 Description of the action taken by the service technician from the service
ticket database for refrigerant use for repairs other than leaks.
DESCRIPTION OF ACTION
Replaced Compressor
Replaced EXV
Replaced Filter Drier
Replaced TXV
Replaced Unit
System Overcharged-Remove Refrigerant
TOTAL
R-22
6
1
1
2
1
11
R-410A
4
1
5
TOTAL
10
1
1
2
1
1
16
at service ports, are corroborated. Corroboration of these
findings could lead to policy changes including earlier
retirement of R-22 equipment and changes to service port
design to reduce emissions.
Acknowledgments
The authors greatly appreciate the maintenance and
operations and administration staff at East Side Union
High School District that supported this project.
Funding Sources
This study was funded by Daikin U.S.
References
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3. UNEP. 2010. " 2010 Report of the Refrigeration, Air
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