44 UV-PRC001-EN
Ducted Applications
Ductwork to the unit ventilator may include outdoor air (OA), return air (RA) and/or discharge air (DA). The unit
ventilator is designed to operate against external static pressures (ESP) thru 0.45”. The ESP is determined by
adding the discharge air static pressure to the greater of either the outdoor air static pressure or the return air
static pressure.
A well designed duct system is beneficial to obtaining satisfactory fan performance. Determining resistance
losses for the duct work system is also necessary for acceptable fan performance. Assistance in the design of
duct work can be found in the ASHRAE Handbook.
Table 19: Static Pressure Percent Air Flow Reduction with Standard Motors
ESP - Inch Water 750 CFM 1000 CFM 1250 CFM 1500 CFM 2000 CFM
0.0625 8 7 10 9 6
0.125 15 14 18 17 12
0.1875 20 20 23 25 16
0.25 25 26 30 31 20
Table 20: Static Pressure Percent Air Flow Reduction with Hi-ESP Motors*
ESP - Inch Water 750 CFM 1000 CFM 1250 CFM 1500 CFM 2000 CFM
0.30 17 11 10 12 12
0.35 20 25 18 20 16
0.40 30 35 26 28 22
0.45 40 45 34 38 29
* Rated airflow @ .25” of static.
Note: It is very important not to over-estimate the ESP and oversize the motor. Too large of a motor
may result in operation problems such as noise, vibration and motor overloading. An example would
be non-ducted application.
A Hi ESP motor is typically specified when a supply-air duct is required. It is not recommended to use
a Hi ESP motor in a non ducted application.
Application
Considerations
Figure 32:
Part load capacity
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