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TRG-TRC014-EN 67
period four
Fan Modulation
notes
A comparison of these static-pressure control methods demonstrates the
energy savings potential. At this representative part-load condition, using the
optimized static-pressure control method allows the supply fan to use only 43%
of its full-load power versus 55% for the supply duct static-pressure control
method.
In addition to the supply fan energy savings, because the optimized static-
pressure control method allows the system to operate as if the static pressure
sensor was at each individual terminal unit, it ensures that no spaces are
“starved” for air. There are also acoustical benefits at part load by operating the
supply fan and VAV terminal units at the lowest possible duct static pressure.
control
control
method
method
airflow
airflow
fan static
fan static
pressure
pressure
fan input
fan input
power
power
% full
% full
-
-
load
load
power
power
Part-Load Comparison
full load
full load
fan outlet
fan outlet
supply duct
supply duct
optimized
optimized
part load
part load
24,000
24,000
cfm
cfm
[11.3 m
[11.3 m
3
3
/s]
/s]
18,000
18,000
cfm
cfm
[8.5 m
[8.5 m
3
3
/s]
/s]
18,000
18,000
cfm
cfm
[8.5 m
[8.5 m
3
3
/s]
/s]
18,000
18,000
cfm
cfm
[8.5 m
[8.5 m
3
3
/s]
/s]
2.7 in. H
2.7 in. H
2
2
O
O
[672.5 Pa]
[672.5 Pa]
2.1 in. H
2.1 in. H
2
2
O
O
[523.1 Pa]
[523.1 Pa]
1.9 in. H
1.9 in. H
2
2
O
O
[473.3 Pa]
[473.3 Pa]
1.5 in. H
1.5 in. H
2
2
O
O
[373.6 Pa]
[373.6 Pa]
22 hp
22 hp
[16.4 kW]
[16.4 kW]
13 hp
13 hp
[9.7 kW]
[9.7 kW]
12 hp
12 hp
[8.9 kW]
[8.9 kW]
9.5 hp
9.5 hp
[7.1 kW]
[7.1 kW]
100%
100%
60%
60%
55%
55%
43%
43%
Figure 94