Greenheck DG / DGX with Direct Spark (470652) - Manual (Page 22)

Direct Spark Ignition Make-Up Air 22
®
Building Pressure Control
- a variable frequency drive is
controlled according to input
from a pressure sensing device.
Turn both knobs to the upper
most pressure setting. You may
have to remove the outdoor
pressure tap tubing. VAV
systems should go to maximum
speed. Set both knobs at the
lowest setting and the VAV
systems should go to minimum
speed.
Reset the correct pressure
limits before starting the unit.
This picture depicts a typical
photohelic setting. Typical
settings are 0.0 inch wc for
the lower pressure setting and
0.10 inch wc for the upper
pressure setting. The needle
indicates a negative building
pressure. During correct
operation, the indicating
needle will remain between or
near the setting needles.
External Signal - a variable frequency drive is
controlled according to input from an external 2-10 VDC
or 4-20 mA signal (by others).
A 2 VDC or 4 mA signal will send the blower to low
speed. The blower will go to maximum speed with a
10 VDC or 20 mA signal.
Variable Kitchen Control - a variable frequency drive
is controlled by input from a remote speed control.
This unit allows automatic adjustment of make-up air
volumes based on varying cooking loads.
Burner Bypass Damper (optional)
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.
Burner Bypass Damper
Burner
Bypass Damper
WARNING
The burner bypass damper is set-up at the factory.
The weights should not be adjusted in the field. The
damper may not fully close during minimum outside
air mode.
70 65 75 80
85 90
60
55
(OPTIONAL)
BLOWER
DIRTY FIL TERS
MAIN V AL VES
EXHAUST
SUPPL Y
HEA T
(OPTIONAL)
PHOTOHELIC
Building
Pressure Control
NOTE
Blower Start-Up, Steps 1-5 should be performed
before the blower is run.
NOTE
For maintenance issues associated with variable
frequency drives, consult the drive’s manual supplied
with the unit. The drives are programmed at the
factory and should not need any adjustment during
installation and start-up. For kitchen applications, the
drive may be located in the kitchen or in the unit.
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. To test
potentiometer operation, turn the
potentiometer to the two extremes.
With variable volume, make sure the
fan goes to maximum and minimum
speed.
When the potentiometer is at 0, the
fan speed will be at its minimum.
When the potentiometer is at 100,
the fan will be at its maximum speed.
2-Speed VFD Motor
A variable frequency drive (VFD) is used on a single
speed motor to control air volumes. The VFD is factory
programmed for 2 speed operation. It can be switched
to low or high speed from a remote control panel. Turn
the fan speed switch on the remote control panel to
each position and confirm that the fan speed adjusts
accordingly.
Variable Volume Operation
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 VFD
motors and modulating blowers. Before the unit is left in
service, the variable volume control system should be
tested.
EXHAUST
(OPTIONAL)
(OPTIONAL)
55 60
65 70 75 80
85
90
SUPPLY
HEAT
DIRTY FILTERS
MAIN VALVES
BLOWERS
Potentiometer
Control
Check Operation - VAV Units
(optional)
Photohelic Gauge
Pressure
Indicating
Needle
Pressure
Setting
Needles
Pressure Setting Knobs