AAON MODGAS-X, Техническое руководство

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MODGAS-X Technical Guide
SEQUENCE OF OPERATION
Operating Modes
Operating Modes
Stand-Alone Mode
When used in Stand-Alone Mode, the MODGAS-X will
modulate the gas valve(s) and stage any additional fixed stages to
maintain the Discharge Setpoint configured on the MODGAS-X
LCD display. The MODGAS-X is activated by a 24 VAC signal
to the HEAT EN Input.
The following are available in Stand-Alone Mode using the LCD
display on the MODGAS-X:
• Status
• Supply Air Temperature Setpoint Adjustment
• Supply Air Reset Temperature Setpoint
• Adjustment
• Force Mode ON/OFF
• Force Valve Position
• Force Relays
• Alarms
Communications Mode
When the MODGAS-X is connected and communicating with
an AAON unit controller via a modular cable, the necessary
information will be passed between the MODGAS-X and the
AAON unit controller to properly operate in the Heating Mode.
If the communication is interrupted between the MODGAS-X
and the AAON unit controller, both boards will show an alarm.
When communication is restored, the alarms will go away.
In this configuration, the Supply Air Temperature Setpoint is set
using the AAON unit controller and the Supply Air Temperature
Reset is calculated by the AAON unit controller.
The following menu screens are available in Communications
Mode using the LCD display on the MODGAS-X:
• Status
• Force Mode ON/OFF
• Force Valve Position
• Force Relays
• Alarms
Normal Operation
The MODGAS-X modulates up to two gas valves (for 0-20 volt
valves) or eight gas valves (for 0-10 volt valves) to maintain a
desired Discharge Air Temperature. It also controls the speed
of the induced draft fan to maintain proper combustion in the
heat exchanger.
Off Mode
1. If the Heating is disabled, the unit will be in the Off
Mode.
2. In this mode, the unit will be completely shut off.
3. The Heat Valve Output will be set to 100%.
4.
Once the unit enters the Off Mode, it will stay in this
mode for at least one minute.
High Fire Mode
1. When Heat is activated, the unit will first go to High
Fire Mode.
2. In this mode, the valve will be forced to 100%—for a
0-20 volt valve, that would be 0 VDC and for a 0-10
volt valve, that would be 10 VDC—and the Fan Relay
will be activated.
3. The unit will stay in this mode for at least 10 seconds.
4. After the initial 10 seconds, the unit will look for
a 3°F temperature rise from the initial Supply Air
Temperature during Stage 1 and will look for a 5°F
temperature rise from the Supply Air Temperature
during additional Modulating Heat stages to exit the
High Fire Mode.
5. The unit could stay in High Fire Mode indefinitely if
it does not see the temperature rise. This is important
because it means that the unit has not seen proof of
fire and starting modulation without proof could cause
damage to the equipment.
6. The Low Speed relay will not be activated during
High Fire Mode.
Mechanical Failure Alarm
NOTE:
This alarm was removed in version 3.06.
1. The Mechanical Failure Alarm will be enabled when
the unit stays in High Fire Mode for more time than the
Mechanical Failure Delay Setpoint—setpoint default
is four minutes.
2. The Alarm is disabled when the failed Heat Stage
goes to Off Mode.