Greenheck DG/DGX Pilot Ignition (470651_IOM) - Manual (Page 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.
Adjustable Bypass Baffle
An adjustable baffle is provided in the lower (bypass)
airstream. The baffle is factory preset, but may require
field adjustment to account for various installation
variables. Adjust to maintain approximately 20% of
total airflow across the burner and 80% through the
bypass.
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.
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,
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
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
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.
Photohelic Gauge
Pressure
Indicating
Needle
Pressure
Setting
Needles
Pressure Setting Knobs
Supply Air
Outside Air
(100-20%)
20%
80-0%
Adjustable
Bypass Baffle
Recirculated Air
(0-80%)
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.
Model DG / DGX Pilot Ignition Make-Up Air 23
®