Greenheck DG / DGX with Direct Spark (464043 IOM) (Pre-2008) - Manual (Page 18)

18
Step 1 Mount Pressure Tap
Using the factory provided bracket, mount the
pressure tap to the outside of the unit. Choose a
location out of the prevailing winds and away from
supply or exhaust fans to assure accurate readings.
Step 2 Run Pressure Tap Lines
A pressure tap line must be run from the pressure tap
mounted on the outside of the unit to the low
pressure tap on the back of the pressure gauge. A
second pressure tap line must be run from the high
pressure tap on the back of the photohelic to the
space. The high pressure line must be run even if the
photohelic is mounted in the space. Fifty feet of
tubing is supplied with the unit.
Step 3 Set the Building Pressure
The pressure gauge is used to set the desired
building pressure. The pressure is set by adjusting the
knobs for the upper and lower pressure limits. Typical
settings are 0.0 in. wc for the lower and 0.10 in. wc for
the upper pressure setting.
Step 4 Check Control System
Before the unit is left in service, the building
pressurization control system should be tested. This
can be accomplished by turning both knobs to the
upper most pressure setting. You may have to
remove the outdoor pressure tap tubing. The return
air damper should close (VAV systems should go to
max speed). Then set both knobs at the lowest
setting, and the damper should open (VAV systems
should go to minimum speed). It may take one to two
minutes for the VFD/damper to reach the desired
position. Reset the correct pressure limits before
starting the unit. The picture on the bottom right
shows a typical photohelic setting. The needle in this
photo indicates a negative building pressure. During
correct operation the indicating needle will remain
between or near the setting needles.
Installation - Building Pressure Control (Optional)
Low Pressure Tap
To Outside
High Pressure Tap
To Space
Factory
Wiring
Pressure Setting Knobs on Pressure Gauge
Pressure Setting
Needles
Pressure Indicating
Needle
Installation
NOTE!
Blower Start-Up, steps 1-4 should be
performed before the blower is run.
Pressure Tap
Building Pressure Settings
Pressure Tap Connection
Back of Pressure Gauge