94 RT-SVX34C-EN
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Economizer Damper Adjustment
Economizer (O/A) Dampers
Arbitrarily adjusting the outside air dampers to open fully when the return air dampers are fully
closed can overload the supply fan motor or deliver higher CFM to the space than designed. This
causes higher operating duct static pressures and over pressurization of the space when the unit
is operating in the "economizer” mode.
The O/A and R/A damper linkage is attached to a plate with a series of holes that allows the installer
or operator to modify the O/A damper travel to compensate for various R/A duct losses. The
purpose of adjusting the amount of O/A damper travel is to maintain a balance or equal pressure
between the O/A dampers and the pressure drop of the return air system. Figure 51, p. 97 illustrates
the damper assembly and Table 46, p. 95 through Table 49, p. 96 list the various damper positions
based on the air flow (CFM) and the return duct losses (static pressure) for Downflow and
Horizontal units.
To adjust the O/A damper for the correct pressure drop:
1. Measure the return duct static pressure.
2. Enter the calculated CFM from the previous section "Verifying Proper Airflow" Tab le 36, p. 85
to obtain the return air damper pressure drop.
Figure 49. (Downflow) Standard Exhaust Maximum Damper Position
Figure 50. (Horizontal) Standard Exhaust Maximum Damper Position
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