WARNING
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12
3.0
AG2 Series Operation • Sequence of Operation • Thermostat • Diagnostics
3.0
Operation
Note: Reference the Tube Heater General Manual for installation requirements.
Sequence of Operation
Standby: The MICRO 60U-24 CONTROL continually checks for internal faults, circuit integrity and relay
contact positioning.
Starting Circuit: Upon a call for heat, the control verifies that the differential switch is in the proper
position (open). The control energizes the fan. Once operational static pressure is achieved, the
differential switch will close initiating the ignition sequence. The glo-bar is powered and the gas
valve opens after 45 seconds. If the flame is not sensed, the heater will attempt to re-ignite for a total
of three (3) trials for ignition before proceeding to soft lockout.
Single Stage Running Circuit: After ignition, the flame rod monitors burner flame. If sense of flame is
lost, the control closes the gas valve within one second and a new trial sequence (identical to the
starting sequence) is initiated. If flame sense is not established within 8.5 seconds, the heater will
attempt two (2) additional ignition sequences before proceeding to soft lockout. The control can be
reset by briefly interrupting the power source.
Two Stage Running Circuit: The second stage on the gas valve is powered directly from the second
stage of the thermostat. In order for two stage to flow to a higher output, single stage must be
energized as well. The thermostat determines which stage to maintain for the desired temperature.
Shut Down: When the thermostat is satisfied, the fan will enter a two (2) minute post-purge cycle. Then
go to diagnostics; soft & hard lockout.
Thermostat
Note: Different thermostats operate according to their particular features. Refer to thermostat
specifications for details.
AG2 Series heaters require a 24V, two-stage thermostat to operate. The burner control box is equipped
with a 36” yellow 24V control wire. Do not supply 120V to the 24V connection.
Theoretical Example: The thermostat is set to 65° F. The thermostat’s preset differential for
high fire mode is 3° F.
When the temperature drops below the setpoint of the thermostat (65° F), low fire will activate. If
the temperature continues to drop below the setpoint by another 3° F (62° F), high fire will activate
bringing the temperature back up to the thermostat’s setpoint quickly.
This heater must be installed and serviced by trained gas installation and service
personnel only.
Do not bypass any safety features or the heater’s built in safety mechanisms will
be compromised.
AG2
Series
