Greenheck DG / DGX with Direct Spark (470652) - Manual (Page 23)

Direct Spark Ignition Make-Up Air 23
®
Check Operation - Recirculating
Units (optional)
NOTE
Blower Start-Up, steps 1-5 should be performed
before the blower is run.
Recirculation Operation
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.
Before the unit is left in service, the recirculation control
system should be tested.
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.
To test potentiometer operation,
turn the potentiometer to the two
extremes. With 80/20 recirculation,
confirm that the return air damper
fully opens and fully closes. When
the potentiometer is at 0, the return
air damper will open. When the
potentiometer is at 100, the return
air damper will close. The damper
actuator may take a few minutes to
open or close.
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 to close.
Turn the recirculating switch on
the remote control panel to each
position and confirm that the return
air damper adjusts accordingly. The
damper actuator may take a few
minutes to open or close.
70 65 75
80
85
90
60
55
(OPTIONAL)
BLOWER
DIRTY FIL TERS
MAIN V AL VES
RECIRCULA TION
EXHAUST
SUPPL Y
HEA T
(OPTIONAL)
2-Position
Damper Control
EXHAUST
(OPTIONAL)
(OPTIONAL)
55
60 65 70 75 80
85 90
SUPPLY
HEAT
DIRTY FILTERS
MAIN VALVES
BLOWERS
Potentiometer
Control
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.
Turn both knobs to the upper
most pressure setting. You may
have to remove the outdoor
pressure tap tubing. The return
air damper should close.
Set both knobs at the lowest
setting and the damper
should open. It may take one
to two minutes for the damper
to reach the desired position.
Reset the correct pressure
limits before starting the unit.
This picture shows a typical
photohelic setting. Typical
settings are 0.0 inch wc for
the lower and 0.10 inch wc
for the upper pressure 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.
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).
The return air damper will close with a 10 VDC or 20 mA
signal. The return air damper should open with a 2 VDC
or 4mA signal. The damper actuator may take a few
minutes to open or close.
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
Photohelic Gauge
Pressure
Indicating
Needle
Pressure
Setting
Needles
Pressure Setting Knobs