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» Support TX1500U

Troubleshooting Poor Temperature Regulation
• This page lists problems that may affect the temperature performance of your LUX thermostat with suggested resolutions.
• For more detailed information please refer to the instructions that came with your thermostat.
The instruction manual for this model can be viewed in PDF format by clicking here.
 
Model TX1500U
   
Problem Resolution
No fan function in heat mode Move the switch or jumper on the circuit board to its ELECTRIC POSITION for electric heat, then confirm with Fan Test below.
Fan On continuously Move Fan switch from ON to Auto.
Remove the "G" wire. If fan continues to run, then either the system is miswired, or the problem is in the system, not the thermostat.
Indicates incorrect room temperature Refer to thermostat  manual to verify that your set temperature is what you expect it to be. The set temperature is always visible with "SET" on the display.
  Refer to your thermostats manual for calibration. Use this feature to adjust the displayed temperature up to +5°F(3°C) or -5°F(3°C) degrees.
No second stage or AUX heating The offset may be set to 0. This needs to be set to at least 1. Refer to wiring to verify that it is wired correctly for your system.
Emergency heat does not turn on Must be set from Furn to HP.  Different versions (a, b, c revisions) of this model have different ways to change setup options.  Some are DIP switches on the circuit board and some are set using the front panel buttons in a menu.  Refer to the user manual for your particular version for option settings.
How do I set my thermostat to act as a manual thermostat? How do I remove the programming? Different versions (a, b, c revisions) of this model have different ways to change setup options.  Some are DIP switches on the circuit board and some are set using the front panel buttons in a menu.  Refer to the user manual for your particular version for option settings.
Heats or cools more than 5 degrees past its displayed set temperature Remove thermostat body from the wall, leave the back plate in place. Verify that heating and cooling switch off within a few minutes.
Replace the units batteries with fresh Duracell® or Energizer® alkaline batteries.
Set unit to heat mode. Adjust set temperature to at least 5 degrees below room temperature. Then adjust set temperature upward one degree at a time. Listen carefully for a soft click from the thermostat. This click should be heard near room temperature.
Refer to your units manual to decrease the units swing setting to a narrower setting.
Verify that your units placement and mounting are optimum per the installation section of its manual. 
Refer to the wiring troubleshooting guide to verify that your thermostat is wired correctly. Insure you are using the correct wiring diagram for your heating/cooling system.
Note that in Cool Mode the thermostat may not activate a cooling stage until its compressor protection time has elapsed this may be a long as 5 minutes.
  Where the wires are coming out of the wall fill the hole with non-combustible insulation or putty to prevent drafts from affecting the the thermostats performance.
No heat or cooling when expected Move the switch or jumper on the circuit board to its ELECTRIC POSITION for electric heat, then confirm with Fan Test below.  Different versions (a, b, c revisions) of this model have different ways to change setup options.  Some are DIP switches on the circuit board and some are set using the front panel buttons in a menu.  Refer to the user manual for your particular version for option settings.
Refer to thermostat manual to verify that your set temperature is what you expect it to be. The set temperature is always visible with "SET" below.
Replace the batteries with fresh Duracell® or Energizer® alkaline batteries. Press HW_RST on the back of the thermostat. It may be  necessary to reconfigure some settings after a reset.
Set unit to heat mode. Adjust set temperature to at least 5 degrees below room temperature. Then adjust set temperature upward one degree at a time. Listen carefully for a soft click from the thermostat. This click should be heard near room temperature. Adjust set temperature down one degree at a time. Again listen carefully for a soft click from the thermostat near room temperature. 
Refer to wiring to verify that it is according to the wiring diagram applicable to your system.
If your system is a low voltage system having 24VAC or less, and you are technically inclined, you may jump terminals as given below out to detect a malfunction in your system. 
Fan Test With the power ON at the fuse box, touch the "G" wire to the "RH" terminal. The fan should come on immediately and stay on. The rush of air is usually heard.
If the fan does not come on it is an indication that there is a problem with your system. Check any breaker or fuses that feed the 24VAC transformer that powers your system.
Heat Test To test gas or oil heating systems, take the "W1" wire off its terminal. With the power ON at the fuse box, touch the "W1" wire to the "RH" terminal for a couple of minutes and the heater should come on and stay on until the wire is removed.
Cooling Test To test cooling, remove the "G" and "Y" wires. Connect them together with the "RC" for several minutes to observe operation. The system should come on and stay on. If the cooling fails to come on, or comes on and off, the problem is in the system.
Heat Pump Test To test a heat pump system with an "O" wire, three wires must be connected together with the power terminal. The power terminal is "RH". With the power ON at the fuse box, connect the "O"  and "Y", and "G" wires to the "RH" terminal for a couple of minutes and the unit should provide cool air. Wait at least 5 minutes and repeat this test without the "O" wire. The unit should provide heat.  
To test a heat pump system with a "B" wire, three wires must be connected together with the power terminal. The power terminal is "RH". With the power ON at the fuse box, connect the "B"  and "Y" and "G" wires to the "RH" terminal for a couple of minutes and the unit should provide warm air.  Wait at least 5 minutes and repeat this test without the "B" wire. The unit should provide cool air.  
Thermostat Emergency Heat Test 1. Set unit to EMER (heat) mode. 
2. Adjust set temperature to at least 5 degrees below the room temperature.
3. Adjust set temperature upward one degree at a time. Wait for the Set temperature to be accepted and replaced by the room temperature. Listen carefully for a soft click from the thermostat. AUX will appear; and HEAT will flash when on.
4. Repeat step 3 until the click is heard or the set temperature is at least 5 degrees above the room temperature. Remember to wait for the Set Temperature to be accepted and replaced by the room temperature before, before making the next adjustment. The click should be heard near room temperature.
5. After the click is heard, adjust set temperature downward one degree at a time. Again listen for a soft click from the thermostat.
6. Repeat step 5 until a click is heard or the set temperature is again 1 degree below the room temperature.
7. Steps 2 through 6 may be repeated to be sure that a click is heard each time the set temperature passes the room temperature.
8. If no click can be heard the thermostat is not operating properly. It must not be used to control a HVAC system until the problem is remedied.
For further assistance: Contact your HVAC service company or our Technical Assistance Line if not resolved.
 
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