I.C.E. BMA-136 HBR - Manual (Page 12)

11
TYPICAL SEQUENCE OF OPERATION MAKE-UP AIR
(WARNING: FOR ACTUAL UNIT SEQUENCE OF OPERATION, PLEASE CONSULT SHOP DRAWINGS)
With Supervisor panel
SUMMER OPERATION:
1. When exhaust interlock contacts close, the damper opens.
2. Exhaust light indicates exhaust on.
3. Damper interlock closes, powering blower motor starter.
4. Blower motor auxiliary contacts close.
5. High limit switch is closed.
6. “Fan” lights indicate that blowers are running.
WINTER OPERATION:
1. Exhaust system interlock contacts must be closed.
2. Exhaust light indicates exhaust on.
3. Interlock circuit on safety relay is closed.
4. When damper is open, end-switch contacts close and energize the blower motor starter.
5. Blower motor starter auxiliary contact closes.
6. Air flow proving switch closes (low).
7. “Fan lights indicate that blowers are running.
8. Summer-winter switch, “on”.
9. Combustion control is energized.
10. Pre-purge timer (optional) is energized and contacts close after predetermined purge period.
11. High gas pressure switch, low gas pressure switch, optional contacts are normally closed.
12. High temperature limit switch is normally closed. Switch must be manually reset if air temperature has
exceeded set point.
13. Outdoor thermostat contacts close when outside air temperature falls below set point (optional).
14. Limit circuit to primary safety control is complete.
15. Ignition transformer is energized and sparks provided.
16. Pilot gas valve opens and pilot is proved.
17. Main gas valve(s) is energized.
18. “Burner” lights indicate that gas valve(s) is energized.
19. Presence of flame is proved by flame rod. Ignition is de-energized and main gas valve remains
open.
20. (Optional) Low limit light stays on indicating that air temperature exceeds setting of low limit
switch. Manual start push button may be disengaged.
21. Modulating temperature control maintains discharge air temperature at a set-point with 30-1 turn-
down ratio.
22. Alarm light indicates flame failure of burner or failure of air proving switch.
NOTE: Sequence of operations is the same on units with summer-off winter switch except that the indicating lights
show blower on and burner switch in the winter position.