19.Door Switch - Model UDAS only
20.Ignition System
All sizes of Model UDAS heaters are equipped with a door switch which prevents the heater from operating when the service door panel is open. The service panel of a Model UDAS is equipped with a pliable gasket material that fully seals the door to provide added protection from building air entering the combustion zone of the heater. (For switch location, see FIGURE 18, page 31.)
This heater is equipped with a direct spark integrated control module (circuit board). The module monitors the safety devices and controls the operation of the fan and venter motors and the gas valve between heat cycles.
FIGURE 14 – DSI Integrated Control Module (circuit board)
| x |
Spark |
|
Transformer | Control Plug |
|
Fuse
Thermostat
Connections
Dip Switch
Fan/Blower
Off
Delay
StatusLED Lights
Lights
Flame Status - Yellow LED Codes
Control Status - Green LED Codes
Steady ON | Normal Operation, No call for heat | |
Fast Flash | Normal Operation, Call for heat | |
1 | Flash | System Lockout, Failed to detect or sustain |
|
| flame |
2 | Flashes | Pressure Switch Did Not Close within 30 |
|
| Seconds of Venter Motor |
3 | Flashes | High Limit or Flame Rollout Switch Open |
4 Flashes | Pressure switch is closed before venter | |
|
| motor is energized |
Steady OFF | Blown Fuse, No Power, or Defective Board | |
Steady ON | Flame is sensed |
Slow Flash | Weak flame (current below 1.0 |
| microamps ±50%) |
Fast Flash | Undesired Flame (valve open |
| and no call for heat) |
Fan/Blower OFF Delay Settings (dip switches)
Off | Off | 120 seconds (factory setting) |
Off | On | 90 seconds |
On | Off | 160 seconds |
On | On | 180 seconds |
Normal Heat Cycle
Operating
Sequence
1)Call for Heat - The thermostat calls for heat by energizing the “W” terminal. The control checks to see that the limit switch is closed and the pressure switch is open. If the limit switch is open, the control responds as defined in the “Abnormal Heat Cycle, Limit Switch Operation”. If the pressure switch is closed, the control will do four flashes on the green LED and wait indefinitely for the pressure switch to open. If the pressure switch is open, the control proceeds to prepurge.
2)Prepurge - The control energizes the venter motor and waits for the pressure switch to close. If the pressure switch does not close within 30 seconds of the venter motor energizing, the control will do two flashes on the green LED. The control will leave the venter motor energized indefinitely as long as the call for heat remains and the pressure switch is open.
Form
