Service manual

19
6-561.2
CONTROL OPERATING SEQUENCE / UNIT COMPONENTS
Upon a call for heat from the thermostat, power is supplied to
the power exhauster motor. The unit will go through a purge
period and then the direct spark igniter will be energized. At the
same time, the main valve in the combination control valve will
open to allow gas to flow to the burners. If the fan motor has
not already started it will start shortly. If a flame is not sensed
within 7 seconds for any reason the main valve will close and
there will be a short purge period before ignition is tried again.
If the flame is not sensed after four tries there will be at least a
one hour wait before ignition is tried again.
CONTROL OPERATING SEQUENCE
Figure 20.1 - Major Gas, Electrical Service, Safety and Other Components
1. Power Exhauster
2. Pressure Switch
3. Integrated Direct Spark Control Board
4. Combination Gas Control
5. Control Transformer
Control Options
Control Description
Control Service Thermostat Type of Model
Code No. Voltage Voltage Gas Size
Single-Stage, Direct Spark Ignition, 100% Shut-Off with Continuous Retry 11 115V 24V natural 30-125
Utilizes a single-stage combination gas control with ignition control.
Gas is lit with a direct spark igniter on call for heat. 21 115V 24V propane 30-125
Two-Stage, Direct Spark Ignition, 100% Shut-Off with Continuous Retry 12 115V 24V natural 75-125
Utilizes a two-stage combination gas control with built-in ignition control.
Firing rate is 100% and 50% of full rated input. Gas is lit with a direct spark
22 115V 24V propane 75-125
igniter on call for heat.
5
2
1
4
3
7
8
8
6
9
10
6. Flame Sensor (hidden)
7. Auto Reset Limit Control (hidden)
8. Direct Spark Igniter (hidden)
9. Gas Pipe Connection
10. Horizontal Air Deflector Blades