ASHRAE Journal - October 2022 - 45

TECHNICAL FEATURE
records to estimate refrigerant leakage in refrigeration
systems.4 No similar studies were found that used
primary data collection to estimate refrigerant leakage
from AC systems. The lack of published primary data on
refrigerant leakage from AC systems is unexpected given
the need to account for and understand refrigerant leakage
in preparing greenhouse gas emission inventories
and for developing policies and regulations to manage
refrigerant use.
Methods
School District Facilities
For this study, refrigerant data was collected and analyzed
over a four-year period (March 1, 2016, through
May 20, 2020 ) at East Side Union High School District
in San Jose, Santa Clara County, California. The district
administers one adult education program and 19 high
schools, of which 11 are traditional high schools and
seven are alternative high school programs. The total
assignable square footage of all the campuses aggregates
to about 220 000 m2 (2.4 million ft2).
HVAC Maintenance and Operations
The director of maintenance and operations of the
school district oversees the operation and repair of real
property facilities and systems, including HVAC systems.
The team handles routine maintenance, preventive
maintenance, deferred maintenance projects, annual
inspections, hazardous waste management, facilities
rentals and energy management.
The HVAC maintenance and operations staff (team of
seven) performs preventative maintenance on HVAC
equipment, which includes quarterly fi lter changes, and
troubleshoots and repairs HVAC systems in response
to complaints from building occupants. The district
purchases HVAC supplies, including refrigerant, from
two refrigeration supply companies. When the skill set
needed for a repair is not available in-house or the time
required to respond to repairs exceeds available staff,
the district uses HVAC service contractors.
Over the study period (March 1, 2016, through May
20, 2020) four service contractors were used. Often, less
experienced district staff assisted the HVAC service contractors
with repairs as a form of training. Over the study
period, the district did not check refrigerant charge as
part of their preventative maintenance protocols. The
district reported that the last time refrigerant may have
been routinely checked as part of a preventative maintenance
protocol was in 2010.
Maintenance and repairs that resulted in refrigerant
use were initiated in response to a comfort complaint
by a building occupant, which includes teachers and
administrative staff. Teachers and administrative staff
can submit service tickets to the district through a webbased
portal, which are managed in a computerized
database. Complaints related to HVAC system performance
(e.g., HVAC not working, too warm, too cold,
thermostat not working) are assigned to the HVAC service
team for investigation. Previous studies have shown
that HVAC systems with refrigerant fl ow metered by a
fi xed orifi ce have a rapid decline in capacity as refrigerant
charge drops (e.g., 80% capacity at 80% charge level).
However, refrigerant charge levels must reach around
70% in systems with refrigerant metered by a thermal
expansion valve before there is a noticeable decrease in
cooling capacity.5
The refrigerant used for maintenance and operations
reported in this study represents the annual amount of
refrigerant used to keep equipment operational without
comfort complaints. The actual refrigerant remaining in
a system at any point in time, and at its point of removal
at end-of-life, may be less than 100%. Those refrigerant
losses are not considered in this analysis and must be
accounted for separately (e.g., by assuming an additional
loss of refrigerant at end-of-life in addition to an
annual amount used for operations).
Researchers performed the study based on review
of historical records; therefore, the behavior of the
employees or their service contractors was not affected
by the study. While the sample is limited to one school
district (because multiple employees and service contractors
serviced equipment), it is expected that the
results are representative of typical practices in servicing
light-commercial HVAC equipment.
HVAC Equipment Inventory
The district inventories their installed mechanical
equipment across all schools in a commercial facility
management software database. The software contains
basic equipment details and, in most cases, a photo of
the equipment and service tag sticker (Figure 1).
The district provided the researchers with access to the
database. Researchers downloaded data for all refrigerant-containing
HVAC systems used for comfort heating
O CTO B E R 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
45
https://www.ashrae.org/
ASHRAE Journal - October 2022

Table of Contents for the Digital Edition of ASHRAE Journal - October 2022
