Greenheck Fan DGX manual Variable MAKE-UP AIR Options, Variable Volume, Recirculation

VARIABLE MAKE-UP AIR OPTIONS

Variable Volume

The variable volume option is recommended when a building’s exhaust volume will vary. The make-up air volume will track with the exhaust volume, providing only the necessary amount of make-up air.

The variable volume option saves energy by reducing both fan power and gas consumption whenever make- up air requirements are less than the maximum.

Airflow Control Strategies

Greenheck offers four methods of controlling the make-up air volume. All four vary the fan speed for maximum energy savings.

•Variable Frequency Drive controlled by building pressure.

•Variable Frequency Drive controlled manually with a remote potentiometer.

•Variable frequency drive controlled by a 2-10 VDC or 4-20 mA signal.

•2 speed motor controlled manually with a remote switch.

Burner By-Pass Damper

The Variable Volume option includes a patented burner by-pass damper, which maintains the pressure drop across the burner as air volumes change. This assures that complete and proper combustion occurs. The by-pass damper is self-adjusting, designed for minimal maintenance, and requires no controls.

Outside Air

Supply Air

Recirculation

The recirculation option is recommended when the ventilation equipment provides the primary source of heating for the space.

Up to 80% of the air from the space can be recirculated and filtered and then combined with a minimum of 20% outdoor air for a continuous source of fresh air. Only outdoor air is used for combustion to eliminate the possibility of contaminants from the recirculated air crossing over the burner.

Airflow Control Strategies

Greenheck offers four methods of controlling the ratio of recirculated air to outdoor air via motorized dampers.

• Modulating actuator controlled by building pressure.

•Modulating actuator controlled manually with a remote potentiometer.

•Modulating actuator controlled by a 2-10 VDC or 4-20 mA signal.

•Two position actuator controlled manually with a remote switch/time clock.

20%

80-0%

Outside Air (100-20%)

Recirculated Air	Supply Air
(0-80%)

Temperature Control

There are three temperature control options for heat: 1) Discharge Control, 2) Space Control, and 3) DDC Interface Control. Cooling controls are by others.

Discharge Control

A factory installed modulating system controls the gas valve to provide the desired temperature based on a sensor at the fan discharge. A room override option is available to boost the discharge temperature when the space is too cool.

Room Control

Specify this option when the DGX has the primary responsibility for controlling the room temperature. A manually adjusted room thermostat provides feedback to the unit controls, which vary the discharge temperature in order to maintain desired room set point.

DDC Interface Control

Allows for an external signal (0-10 VDC or 4-20 mA) from the building management system to modulate the burner output to satisfy monitored conditions.

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