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» Support DHP2120

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 DHP2120
   
Problem Resolution
Fan on continuously Move Fan switch from ON to Auto
Remove the "G" wire. If fan continues to run, then either the system is mis-wired, 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" below.
Heats or cools more than 5 degrees past its displayed set 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" below.
Remove thermostat body from the wall, leave the backplate in place. Verify that heating and cooling switch off within a few minutes.
Replace the unit's 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 unit's 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.
No heat or cooling when expected 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.
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 reset with small Phillips screw driver. 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. 
The brass contacts in your thermostat may need to be cleaned and/or tightened. Each contact is comprised of a pin protruding from the rear of the thermostats circuit board, and two V shaped contacts on its wall plate. These contacts are located above each screw terminal.  Insert a small regular screw driver at one side of a "V" contact. Turn the screw driver to slightly bend the top of each "V" contact toward its mate.
Refer to wiring to verify that it is according to the wiring diagram applicable to your system.
Advanced Trouble Shooting 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 FAN TEST: Test your system fan first.
With the power ON at the fuse box, touch the "G" wire to the "R" terminal. The fan should come on immediately and stay on. The rush of air is usually easily 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. 
If it persists, contact qualified service personnel for aid in determining the fault.
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 "R". With the power ON at the fuse box, connect the "O" and "Y", and "G" wires to the "R" 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 "R". With the power ON at the fuse box, connect the "B" and "Y" and "G" wires to the "R" 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.  
Contact your HVAC service company or our Technical Assistance Line if not resolved.
Thermostat Emergency Heat Test 1. Set unit to EMER (heat) mode.
2. Adjust set temperature to at least 5 degrees below room temperature.
3. Adjust set temperature upward one degree. Wait for the Set temperature to be accepted and replaced by the room temperature. Listen carefully for a soft click from the thermostat.
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, Afterward the flame will flash.
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 5 degrees below the room temperature. The flame will again be steady.
8. Steps 2 through 6 may be repeated to be sure that a click is heard each time the set temperature passes the room temperature.
9. 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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