Pother =
Pbuilding −
PHVAC, (3)
where Pbuilding is the total building load. (Pbuilding was corrected for
PV power production after installation of the BIPV system.) PHVAC
is the total HVAC power load, calculated as
PHVAC =
Pc1 +
Pc2 +
Pahu1 +
Pahu2 +
Pec. (4)
Subscripts c, ahu, and ec denote the compressor, air handler, and
evaporative condenser, and subscripts 1 and 2 correspond to components
for the south side of the building (AHU1) and the north
side of the building (AHU2).
Measurements were recorded by a pair of Campbell Scientific
XP-CR1000 24-bit programmable data loggers. The instrumentation
and data loggers were installed and commissioned in early
December 2008. Each sensor was scanned once a second and average
values were recorded every 30 s.
2.4. HVAC system repairs
Multiple repairs were performed on the HVAC system. In late
April 2009 there was a failure of the fan starter in the evaporative
condenser blower. At the same time compressor 2 was found to
be low on refrigerant. Both issues were repaired and refrigerant in
compressor 2 was recharged. On 7 July 2009 the disconnect to AHU2
was rewired because its blower motor was found to be running in
reverse. It is assumed that the blower motor was running in reverse
during all data collection prior to the repair on 7 July 2009.
2.5. Data analysis methods