5
MODGAS-X Technical Guide
OVERVIEW
General Information
Overview
The MODGAS-X Module is designed to modulate up to two
gas valves to maintain a desired Discharge Air Temperature. The
MODGAS-X also controls the speed of the induced draft fan to
maintain proper combustion in the heat exchanger. See
Figure 1,
page 6
for dimensions.
The module can be used in Stand-Alone Mode or Communications
Mode with an AAON unit controller. The MODGAS-X connects to
an AAON unit controller or expansion module via a modular cable.
Depending on the type of AAON unit controller, this connection
will utilize an I
2
C connection or an E-BUS connection. See
page 9
for wiring details.
The MODGAS-X can be configured at the factory for one of the
following configurations:
• One modulating valve
• Two staged modulating valves
•
One or two modulating with multiple fixed staged
valves (Stand-Alone Mode only)
The MODGAS-X can be configured at the factory for the
MAXITROL
®
0-20 volt valve(s) or the MAXITROL
®
EXA
STAR 0-10 volt stepper valve(s). See
Appendix C, page 36
for depiction.
When using the MODGAS-X to replace an existing MODGAS II,
see
Appendix B, page 35
for details.
Features
The MODGAS-X provides the following:
• Monitors Supply Air Temperature and Supply Air Reset
and modulates gas valve(s) to maintain Setpoint
• Provides proper control of the Induced Draft Fan
• Provides additional options for Stand-Alone control
• Contains a 2 x 8 LCD character display and four buttons
that allow for status display, setpoint changes, and
force modes
NOTE:
The MODGAS-X contains no user-serviceable
parts. Contact qualified technical personnel if
your MODGAS-X is not operating correctly.
