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MODGAS-XWR2 Technical Guide
Operation Modes
The MODGAS-XWR2 can be used in Stand-Alone Mode or
connected to a AAON unit controller using an E-BUS or modular
cable.
Stand-Alone Mode
When used in Stand-Alone Mode (not connected to a AAON unit
controller), the MODGAS-XWR2 will modulate the gas valve(s)
to maintain the Supply Air Temperature Setpoint congured on
the MODGAS-XWR2. The MODGAS-XWR2 is activated by
a 24 VAC signal to the HEAT EN input.
The following setpoints are adjustable on the LCD display in
Stand-Alone Mode:
• Supply Air Temperature Setpoint
• Supply Air Reset Temperature Setpoint
Communications Mode
When the MODGAS-XWR2 is being used with an AAON
unit controller, information will be transferred between them
via a modular or E-BUS cable, depending on the type of unit
controller used.
In this conguration, the MODGAS-XWR2 uses the Supply Air
Temperature from the AAON unit controller for control. The
Supply Air Temperature Setpoint and Supply Air Temperature
Reset values are set by the AAON unit controller.
If communication is interrupted between the MODGAS-XWR2
and the AAON unit controller, both boards will indicate an
alarm. The alarm condition will be cleared once communication
is restored.
Min Mode
Min Mode is used to help eliminate overshoot of the Supply Air
Temperature Setpoint as additional stages of heat are activated.
When Min Mode is active, the modulating valves are commanded
to Min Position until the interval timer has expired. To disable
Min Mode, set the Min Mode deadband to zero.
The Min Mode works in the following order:
1. The Min Mode will attempt to initialize after the rst
stage of heat and any subsequent stage of heat.
2. If the Supply Air Temperature is below the Supply
Air Temperature Setpoint and within the Min Mode
deadband, Min Mode will run for a user dened
interval.
3. After the interval, the valve will modulate normally
to maintain the Supply Air Setpoint.
SEQUENCE OF OPERATION
Operating Modes and Min Mode
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