Greenheck TSU Direct Gas Manual (456857) - Manual (Page 6)

6
Sequence of Operation
This is included to help in determining if the unit is functioning properly upon initial startup.
Control Center
1. Turn the fan switch to the “on” position or the Summer/off/Winter switch to the "Winter"
position.
2. (Optional) Damper actuator is energized.
3. Supply starter is energized. Supply fan runs*.
4. Turn the heater switch “on”, if using separate switches.
Heater
5. Open all manual gas valves.
6. High temperature limit switch contact is closed (normally closed).
7. Optional high/low gas pressure switch contacts are closed (high pressure is
normally closed, low pressure is normally open).
8. Optional inlet air sensor contact is closed.
9. Airflow sensing switch contact is closed (normally open).
10. Flame safeguard starts cycle.
A. 10 second initiation period
B. 10 second purge
C. Spark generator will be energized for 10 seconds and the pilot solenoid valve will
be energized
D. Pilot flame signal will be sensed
E. With proof of pilot after 10 seconds, the main solenoid valves will open. The
optional vent valve will close at this time
F. Flame will be continually checked by safeguard
11. Maxitrol system will adjust to maintain the required discharge temperature.
NOTES:
*1. If exhaust starter is included, it must operate first before the supply starter.
2. If an off delay timer (1-120 minutes) is included, the unit will continue to operate
after the switch is turned to the off position.
3. If freeze protection is included, a timer (1 to 5 minutes) and a discharge
temperature sensor is included. The unit must heat up to above the discharge
temperature before the timer runs out or the unit will shut off.