Detroit Radiant Products Company QTS Series - Manual (Page 35)

QTS Series
35
4.0 Operation • Sequence of Operation
WARNING
!
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.
Sequence of Operation
When operating under standard configuration, two voltages (120VAC supply and 24VAC control)
must be supplied to the QTS series unit.
Starting Circuit: Upon a call for heat the dual pole relay sends 24V through the post purge timer
energizing the fan relay. The relay is closed sending 120VAC to the blower. Once operational static
pressure is achieved, the differential pressure switch closes, sending power to the ignition module.
After a seven-second pre-purge, the spark igniters and the solenoid of the gas valve are
simultaneously energized. The trial for ignition is 15 seconds.
Running Circuit: After ignition, the control monitors burner flame through the flame sensors. If sense of
flame is lost, the control immediately sparks (identical to the starting sequence). If flame sense is not
established within 15 seconds, the heater will attempt two (2) additional ignition sequences before
proceeding to lockout mode. The control can be reset by briefly interrupting the power source.
Shut Down: When the thermostat is satisfied, the fan will enter a 90 second post-purge cycle.