Appendix M: Enthalpy Wheel Pressure Drop
vs. Flow Formulae and Curves
Enthalpy Wheel Pressure Drop vs. Flow
Formula
Flow in cfm = pressure drop measured in inches w.c. /
pressure drop coefficient based on enthalpy wheel size
Enthalpy Wheel Pressure Drop vs. cfm
Curves (based on wheel diameter x depth
(inches) x efficiency)
Table M1: Enthalpy Wheel Pressure Drop Coefficient
Enthalpy Wheel Size
(diameter x depth in inches)
Pressure Drop Coefficient
Supply
Exhaust
36 x 4 (standard)
0.000515270 0.000430623
36 x 8 (high)
0.000331429 0.000276828
42 x 4 (standard)
0.000361694 0.000311503
42 x 8 (high)
0.000234270 0.000200252
50 x 4 (standard)
0.000256441 0.000224715
50 x 8 (high)
0.000164571 0.000144459
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
0.4
0.3
0.1
0.2
0.0
0
500
1,000
1,500
2,000
2,500
3,000
Airflow [cfm]
Pr
essur
e Dr
op [in. w
.g.]
36” x 8”
(Supply)
36” x 8”
(Exhaust)
36” x 4”
(Supply)
36” x 4”
(Exhaust)
Figure M1: Pressure drop – 36” enthalpy wheel
diameter
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
0.4
0.3
0.1
0.2
0.0
0
500
1,000 1,500 2,000
2,500 3,000 3,500
4,000
Airflow [cfm]
Pr
essur
e Dr
op [in. w
.g.]
42” x 8”
(Supply)
42” x 4”
(Supply)
42” x 8”
(Exhaust)
42” x 4”
(Exhaust)
Figure M2: Pressure drop – 42” enthalpy wheel
diameter
0.5
0.6
0.7
0.8
0.9
1.1
1.2
1.3
1.0
0.4
0.3
0.1
0.2
0.0
0
1,000
2,000
3,000
5,000
6,000
4,000
Airflow [cfm]
Pr
essur
e Dr
op [in. w
.g.]
50”x 8”
(Supply)
50” x 4”
(Supply)
50” x 8”
(Exhaust)
50” x 4”
(Exhaust)
Figure M3: Pressure drop – 50” enthalpy wheel
diameter
VCES-VHC-IOM-1F – VHC-36, -42 & -50
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