Greenheck DG / DGX with Direct Spark (464043 IOM) (Pre-2008) - Manual (Page 29)

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Operation - VAV / Recirculating Units
Operation
The self-adjusting burner bypass damper is a device used in variable volume units. Its function is to maintain
proper combustion by providing a constant airflow over the burner when outside air volumes are changed. It is
located underneath the burner as shown in the picture below.
Variable Volume Operation (Optional)
WARNING!
The burner bypass damper is set-up at the
factory. The weights and springs should not be
adjusted in the field. The damper may not fully
close during minimum outside air mode.
The variable volume option is recommended when a building’s exhaust volume may vary. This option enables the
make-up air volume to track with the exhaust volume, providing only the amount of make-up air required. Control
strategies include 2-speed and modulating blowers.
2-Speed
• A 2-speed motor is used to control air volumes. The motor can be switched to low or high speed
from a remote control panel.
Modulating
• Potentiometer Control - a variable frequency drive is controlled by input from a remote speed
selector (potentiometer). This unit allows easy manual adjustment of make-up air volumes.
• Building Pressure Control - a variable frequency drive is controlled according to input from a
pressure sensing device.
• External Signal - a variable frequency drive is controlled according to input from an external 2-10
VDC or 4-20 mA signal (by others).
Variable Frequency Drives
For maintenance issues associates with the variable frequency drives, please consult the drive’s manual
supplied with the unit. The drives are programmed in the factory and should not need any adjustment during
installation and start -up. For kitchen applications, the drive may be located in the kitchen, not in the unit.
Burner Bypass Damper (Optional)
Burner Bypass Damper