OPERATION MODES & STAGING CONFIGURATIONS
19
MODGAS-XWR-1 Technical Guide
Operation Modes & Staging Con
fi
gurations
Operation Modes
The MODGAS-XWR Controller can be used stand-alone or connected
to a Main Controller using a modular cable (communicating).
Stand Alone Mode
When used in a stand-alone application (not connected to a Main Control-
ler via a modular cable), the MODGAS-XWR Controller will modulate
the gas valve(s) to maintain the DISCHARGE setpoint confi gured on
the MODGAS-XWR Controller LCD display. The MODGAS-XWR
Controller is activated by a 24VAC signal to the HEAT EN input.
The following describes the setpoints available in stand-alone mode for
adjustment using the LCD display on the MODGAS-XWR Controller:
•
Supply Air Temperature Setpoint
•
Supply Air Reset Temperature Setpoint
Communicating Mode
When the MODGAS-XWR Controller is connected to a Main Controller
via a modular cable, the necessary information will be passed between
the MODGAS-XWR and the Main Controller to properly operate in
the Heating Mode.
If the communication is interrupted between the MODGAS-XWR Con-
troller and the Main Controller, both boards will show an alarm. When
communication is restored, the alarms will go away.
In this confi guration, the Supply Air Temperature Setpoint is set using
the Main Controller and the Supply Air Temperature Reset (if used) is
calculated by the Main Controller. The Supply Air Temperature is sent
to the MODGAS-XWR from the Main Controller.
MODGAS-XWR Staging Con
fi
gurations
The MODGAS-XWR can be confi gured for various Staged Heat con-
fi gurations. These confi gurations can be used in conjunction with the
VCM-X E-BUS Controller, VCB-X Controller, VCCX2 Controller, or
12 Relay E-BUS Expansion Module
.
MODGAS-XWR Stand-Alone Con
fi
guration
The fi rst and second confi guration screens designate the Primary and
Secondary boards if using two MODGAS-XWR-1’s.
The third confi guration screen allows selection of Stand-Alone Auto
(no 12 Relay board) or Stand-Alone Forced (using the 12 Relay board).
The fourth confi guration screen allows selection of the Total Stages,
which is the number of Heat Stages installed in the unit (note that if there
are two heat units to be operated in a primary/secondary arrangement,
this is considered 1 stage of heat).
The fi fth confi guration screen selects the confi guration. The options
for Stand-Alone operation are (1) 1 modulating, 1 ignitor, 1 stage, (2)
2 modulating, 2 ignitors, 1 stage, (3) 2 modulating, 2 ignitors, 2 stages
(which allows a secondary MODGAS-XWR-1), and (4) 2 modulating,
1 ignitor, 1 stage (which allows a secondary MODGAS-XWR-1).
MODGAS-XWR Stand-Alone with 12-Relay
E-BUS Expansion Module
In order for the MODGAS-XWR to communicate properly to the 12
Relay Expansion Module, “S/A MODE” needs to be confi gured to
“FORCED”. This confi guration will make the MODGAS-XWR initi-
ate communications with the 12 Relay Expansion Module through the
E-BUS cable.
MODGAS-XWR Communicating with AAON
Unit Controller
The fi rst and second confi guration screens designate the Primary and
Secondary boards if using two MODGAS-XWR-1’s.
The fourth confi guration screen allows selection of the Total Stages,
which is the number of Heat Stages installed in the unit (note that if there
are two heat units to be operated in a primary/secondary arrangement,
this is considered 1 stage of heat).
If more stages of heat are needed besides the MODGAS-XWR and the
main control board’s confi gurable relays, a 12 Relay E-BUS Expansion
Module or an additional expansion board can be connected to the Main
Controller and heat stages can be confi gured for the 12 Relay board from
the Main Controller. If using the 12 Relay board, the third confi guration
screen must be set at Stand-Alone Forced.
The fi fth confi guration screen selects the confi guration. The options
for Stand-Alone operation are (1) 1 modulating, 1 ignitor, 1 stage, (2)
2 modulating, 2 ignitors, 1 stage, (3) 2 modulating, 2 ignitors, 2 stages
(which allows a secondary MODGAS-XWR-1), and (4) 2 modulating,
1 ignitor, 1 stage (which allows a secondary MODGAS-XWR-1).
NOTE:
The Primary/Secondary confi guration is not supported
when using the VCM-X E-BUS Controller.
The status screen displaying the stage status will show the current heat
stage of all heat stages on the unit. For example, if two stages are active
on the MODGAS-XWR and two stages are active on the main control
board, the current heat stage displayed will show HEAT STAGE 4.
