Installation Operation Maintenance

OptionsExhaust fansThe exhaust axial fans are used tominimize the overpressure in thebuilding caused by the introductionof fresh air.This option is typically used whenthe fresh air intake needed isbetween 40 to 50% of the nominalair flow or when the return air ductpressure drop is higher than 25 Pa.This option includes hoods, gravitydampers and two axial fans.(Figure 13)Both fans work always synchronizedwith one stage.A potentiometer installed in the Airinlet section allows to adjust theexhaust fan set point,corresponding to the fresh airdamper position.When the supply air fan is ON, theexhaust fans turn on whenever theposition of the fresh air dampersmeet or exceed the exhaust fan setpoint. (If the potentiometer is set at40%, the exhaust fans will startwhen the fresh air dampers willmeet or exceed 40% opening).Table 12 - Exhaust fan performancesFigure 13 - Fresh air and power exhaust fans3A. Side view showing fresh air andpower exhaust hoods fordownflow configuration1. Fresh air hood2. End of unit3. Power exhaust hood1A22B. Side view showing powerexhaust hoods for horizontalconfiguration1. End of unit2. Power exhaust hoodB1External Static Pressure (Pa)ExhaustAirflowStep 1ESPStep 2ESPm 3 /h Pa Pa1690 186,8 1992560 169,4 1943380 162 1874250 130 1795110 105 1695940 77 1626800 62 1527630 37 1408500 0 1309360 11510190 10511050 9011880 7712740 6213610 5014440 3715300 2516130 1016990 0Notes:1. Step 1 = 1 exhaust fan motor operating.Step 2 = 2 exhaust fan motor operating.2. Power Exhaust option is not to be applied onsystems that have more return air static pressuredrop than the maximum shown in the table foreach motor speed tap.28RT-SVX16C-E4