Installation manual

IM-487 Page 37

Mixing Box (RAH 47-77 only)

This section utilizes an outside air damper and a return air

damper. Use of these dampers allows outside air to be

blended with return air. Synchronized operation of the

dampers is accomplished by interconnecting rods. As one

damper section opens, the other section is being closed.

Always a total of 100% CFM is drawn from this section.

Damper positioning may be either manually or automati-

cally adjusted. With a field installed controller, automatic

operation can be obtained.

These dampers provide a similar function to the economizer

dampers. This option differs from an economizer in that no

unit mounted exhaust dampers are provided.

Figure 40. Mixing Box

Note: For good airflow control, adjust linkages so damper blades do not open beyond 70 degrees. Opening a damper blade

beyond 70 degrees has little effect on its airflow. Do not "overclose " low leak damper blades. The edge seal should just

lightly contact the adjoining blade. The blades will lock-up if they are closed so far that the seal goes over center.

CLOSED

OPEN

90∞

STROKE

.25" (6 mm)

.75"

(19 mm)

3.00"

(76 mm)

CLOSED

OPEN