Trane Gas Unit Heaters Katalog

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 UH-PRC002-EN
Sequence of Operations
Two-Stage Control
With power applied to the unit:
1.
The first stage of the thermostat calls for heat.
2. The pilot valve opens.
3. The ignitor sparks continuously to ignite the pilot.
4. The sensor proves pilot ignition and shuts off the ignitor.
5. With the pilot lit, the main gas valve opens to low fire.
6. Main burners are lit at 50 percent of unit’s rated input.
7.
The fan time delay relay (optional on duct furnaces) allows the heat exchanger to come up to 
operating temperature. At this time, the fan time delay relay closes and activates the fan motor.
1
8. If additional heat is required, the second stage of the thermostat calls for heat.
9. The main gas valve opens to full fire. The main burners are now at full fire. The unit continues 
at full fire until the second stage of the thermostat is satisfied and no longer calls for heat.
10. The main valve closes to low fire. The main burners are now at low fire. The unit continues at 
low fire until the first stage of the thermostat is satisfied and no longer calls for heat.
11. The main and pilot valves close.
12. The fan time delay relay remains closed, keeping the fan operating to dissipate residual heat 
from the heat exchanger. At this time, the fan time delay relay opens and deactivates the fan 
motor.
Note: This unit is equipped with a blocked vent shutoff (spill) switch. If the venting system 
becomes blocked or there is continuous spillage, the vent shutoff switch will shut off the unit 
heater.
1
See 
Caution - Disconnect power before 
servicing.
Unit must be grounded.
Use copper conductors only.
If any of the original wire as supplied 
with the appliance must be replaced, 
it must be replaced with wiring 
material having a temperature rating 
of at least 125°C.
High-limit and blocked vent (spill) 
wires minimum 200°C.
Refer to installation instructions for 
venting, gas piping, and start-up 
procedures.
 - - - Indicates Field Wiring.
 ___ Indicates Factory Wiring.