Lux thermostat support THC15 Troubleshooting poor temperature

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.
Model
TX100E
Problem
Resolution
Move the jumper on the circuit board to its
ELECTRIC POSITION for electric heat, then
confirm with Fan Test below.
No fan function in heat mode
Move Fan switch from ON to Auto.
Fan ON continuously
Indicates incorrect room
temperature
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.
Refer to thermostat manual to verify that your set
temperature is what you expect it to be. The set
temperature is visible by pressing either the up or
down button once.
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.
How do I set my thermostat to
act as a manual thermostat?
How do I remove the
programming?
Move the System Mode switch to the OFF position,
and then hold down the SET button for
approximately 5 seconds until the screen changes..
Scroll to item #02 (programming style). Select
option 3 for manual non-programmable mode.
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 unit's batteries with fresh Duracell® or
Energizer® alkaline batteries.
Heats or cools more than 5
degrees past its displayed set
temperature
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 unit's 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 thermostats
performance.
Move the jumper on the circuit board to its
ELECTRIC POSITION for electric heat, then
confirm with Fan Test below.
Refer to the thermostat manual to verify that your
set temperature is what you expect it to be. The set
temperature can be viewed by pressing the up or
down button once.
Replace the batteries with fresh Duracell® or
Energizer® alkaline batteries.
No heat or cooling when
expected
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 wired correctly for
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 to detect a
malfunction in your system.
Fan Test
Heat Test
With the power ON at the fuse box, short 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
circuit breaker or fuses that feed the 24VAC
transformer that powers your system.
To test gas or oil heating systems, remove the "W"
wire off its terminal. With the power ON at the fuse
box, short the "W" wire to the "RH" terminal for a
couple of minutes and the heater should come on
and stay on until the wire is removed. If the heating
fails to come on, or comes on and off, the problem
is in the system.
Cooling Test
Heat Pump Test
For further assistance:
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.
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.
Contact your HVAC service company or our
Technical Assistance Line if not resolved.
Wiring Information and Troubleshooting
 This page provides general guidance for wiring your LUX 24VAC electronic thermostat.
For more detailed information please refer to the instructions that came with your
thermostat.
 Please make specific note regarding LOW VOLTAGE and LINE VOLTAGE directions. Do
not install LINE VOLTAGE wires to a LOW VOLTAGE control. Improper installation of a
"C" wire may cause damage to your system.
 Do no install a wire labeled "TC" from the previous thermostat to any of our controls.
Installation of a "TC" wire may cause damage to your system.
 Do NOT wire by color of the wire, wire by the LETTER designation to which the wire was
attached on the previous control.
 If there were no letter designations on your old thermostat, contact our Technical
Assistance Department for assistance.
Model
TX100E
Problem
ALL
Resolution
Never connect a low voltage thermostat to line
voltage.
Wire Color coding
When removing old thermostat, use the wire labels
provided to label wires according to their terminal
connection and not their color. This is because not
all installers adhere to the industry color code
standard. Miswiring may damage thermostat, start a
fire, void warranty or cause injury.
If unsure how to connect your
current wires
Contact our Technical Assistance Line or your
HVAC service company.
Two wires control - heat only
system
Connect one wire to W and the other to RH leaving
in the factory installed jumper wire between RH and
RC.
Two wires control - cool only
system
Connect one wire to RC leaving in the factory
installed jumper wire between RH and RC and the
other to Y.
Two wires control heating AND Currently no Lux controls are compatible with this
cooling.
system.
Three wires for forced air heat
Connect the 24-volt transformer wire to RH. Leave
only system, where the
jumper connecting RH to RC. Connect the forced air
previous thermostat did not
heat system to W, and the fan wire to G.
have a clock or timer
Three wires control heating
and cooling. One wire
operates heat, one operates
cooling and the third provides
24 VAC
Connect the 24-volt system power wire to RH. leave
the jumper wire connecting RH to RC. Connect the
heating wire to W1, and the cooling wire to Y.
Three wires control a cooling
only system. One wire
Connect the 24-volt system power wire to RC.
operates the compressor, one
Connect the cooling wire to Y and the fan wire to G.
operates the fan and the third
provides 24 VAC
Four wires control a heating
and cooling, electric, gas or oil,
forced air system that is NOT
a heat pump
Connect the 24 VAC transformer wire to RH or RC.
Leave jumper wire connecting RH to RC . Connect
the heat wire to W, the cooling wire to Y and the fan
wire to G.
Four wires control a Single
Stage Heat Pump. They were
labeled: G, Y, R or RH or RC,
and either B or O was used
Select either B or O using jumper on circuit board.
Connect the reversing valve wire, either B or O,
(based on jumper connection) to terminal B/O. Keep
jumper wire from RH to RC installed. Connect the 24
VAC wire to RH. Install a second jumper wire
(provided) from W to Y . Connect compressor wire to
Y and the fan wire to G. From setup menu, select
item #06 (system/equipment type) and then option 2
(HP). Set the GAS/ELECTRIC Jumper on the circuit
board to the ELECTRIC position.
Auxillary heat
If your previous thermostat has an auxillary heat
wire, this model is not compatable with your system.
System Power
This thermostat is capable of running on system
power only, battery power only, or both. This is
achieved by connecting the common wire from the
system 24V transformer to the "C" terminal of the
thermostat.
For further assistance:
Contact your HVAC service company or our
Technical Assistance Line if not resolved.
Troubleshooting the Display
 Problems that may be identified from the display of your programmable thermostat are
listed here with suggested resolutions.
 For more detailed information please refer to the instructions that came with your
thermostat.
Model
TX100E
Problem
Display will not change
Resolution
Peel protective plastic label from display.
Peel protective plastic label from display.
Display blurred and unreadable
Blank or fading display
Press the small round HW_RESET button on the
rear of your unit
Replace thermostat batteries with fresh AA size
Duracell® or Energizer® alkaline batteries. Be
sure that they are installed with their polarity (+
and -) correct.
Clean battery contacts with a pencil eraser and
pry out the spring contact slightly to insure a
clean, firm connection.
Display is locked or will not
respond
Displays reads "LO BATT"
Press the NEXT button 3 times then press the
HOLD button once (NEXT-NEXT-NEXT-HOLD).
This button sequence locks and unlocks the
thermostat.
Replace thermostat batteries with fresh AA size
Duracell® or Energizer® alkaline batteries. Be
sure that they are installed with their polarity (+
and -) correct.
Clean battery contacts with a pencil eraser and
pry out the spring contact slightly to insure a
clean, firm connection.
Display reads "OVERRIDE"
"Override" appears on the display when the set
temperature is raised or lowered from the
program temperature. Overrides are terminated
at the next scheduled program period when the
unit will revert to the program temperature and
the "Override" indicator will be extinguished.
Displays wrong room
temperature.
See Temperature Regulation.
Move the System Mode switch into the OFF
position, and then hold down the SET button for
You want to change the displayed
approximately 5 seconds until the screen
temperature scale from °F to °C
changes. Scroll to item#1 (temperature scale).
or from °C to °F
Option1 displays temperature in Fahrenheit and
option 2 displays temperature in Celsius.
Shows "HI" or "LO"
This means Out of Limit. The sensor is reading
outside the thermostats display limit. Room
temperature will reappear when the temperature
returns to normal range. If actual room temp is
not below freezing or above 99F/32C degrees,
there may be a malfunction. Press the HW
RESET button on the circuit board to reset.
For further assistance:
Contact your HVAC service company or our
Technical Assistance Line if not resolved.
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