Greenheck DG / DGX with Direct Spark (464043 IOM) (Pre-2008) - Manual (Page 30)

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Operation
Operation - VAV / Recirculating Units
Recirculation Operation (Optional)
The recirculation operation option is recommended when the ventilation equipment provides the primary source
of heating for the space. A minimum of 20% outdoor air is mixed with up to 80% filtered recirculated air. Control
strategies include 2-position and modulating dampers.
2-Position Damper
• A 2-position spring return actuator is used to control the return air amounts. The damper moves
from open to closed. If power is cut to the unit, the outdoor air damper will fail close.
Modulating
• Potentiometer Control - a modulating spring return actuator is used to control the return air
amounts. The return air damper modulates from fully open to fully closed based on a signal from a
remote potentiometer.
• Building Pressure Control - a modulating spring return actuator is used to control the return air
amounts. The return air damper modulates from fully open to fully closed based on a signal from a
remote pressure sensing device.
• External Signal - a modulating spring return actuator is used to control the return air amounts.
Return air damper modulates from fully open to fully closed based on an external 2-10 VDC or 4-20
mA signal (by others).