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Why is my floor heat not working even though there are no error messages on my thermostat?
If your underfloor heating system is not working properly but there are no error messages on your thermostat, the problem is usually caused by one of the following:
- The thermostat is not programmed correctly
- The set temperature is lower than the current floor temperature
- An uninsulated concrete subfloor is increasing heat-up times
- There is an issue in the wiring or power supply
- There is a fault in the heating cable or thermostat that has not triggered an error code
Follow the troubleshooting steps below to identify the cause and restore your underfloor heating system to proper functionality.
| What to Check | Why it Matters |
| Heating Indicator | Confirms that the thermostat is calling for heat |
| Heat Schedule Programming | Incorrect programming may have the system heating at undesired times |
| Target Temperature | Heating won’t activate if the thermostat’s set temperature is too low |
| Floor Construction | Cables installed deeper in the floor construction will take longer to heat up the floor surface |
| Insulation | Lack of insulation can lead to downward heat loss, increasing heat up times |
| Supply Voltage | Incorrect supply voltage can prevent heating by not providing the system with enough power |
| Resistance Readings | Confirms integrity of the heating cables |
Why isn’t the thermostat displaying an error?
Our thermostats only detect and consider certain parameters to be errors, including:
- Sensor failures
- Ground faults
- Communication issues
Other problems such as:
- Incorrect programming
- Incorrect supply voltage
- Damaged heating cables
- Slow heat transfer
may not generate an error message but can still impact the performance of the underfloor heating system.
Check your thermostat settings.
The thermostat itself is the first place to check. If the thermostat isn’t calling for heat, the floor will not warm and there will not be an error message.
Is the heating indicator on?
Look for the heating indicator on your thermostat. This will either appear as an icon on the thermostat’s screen or a small light in the top corner of the thermostat, depending on the model.
- If the Heating Indicator is On: The thermostat is calling for heat and sending power to the floor. If the floor does not feel warmer after adequate heating time, continue to the next troubleshooting steps.
- If the Heating Indicator is Off: The thermostat is not calling for heat. Review the thermostat’s heating settings.
Is “heating off” enabled?
Look for a message that reads “heating off” on your thermostat’s screen. Verbiage may differ depending on the thermostat model.
- If the “Heating off” Message is Present: The heating has been previously turned off but not turned back on. This will override any existing heating schedules or settings. Press the “heating off” message on the screen to resume scheduled programming. This can also be done through the settings menu.
- If Ther is No “Heating off” Message: The thermostat is not impacted by an override to pause any heat settings. Review the thermostat’s scheduled heating times and settings.
Are the heating schedules correct?
Navigate to the thermostat’s “heating schedules” setting. Check the start and end times that the thermostat is scheduled to heat the floor for each day to ensure that the correct times are selected.
Also verify that the current date on the thermostat is correct and the current time on the thermostat is correct
- If the Heating Schedules are Incorrect: Edit the thermostat’s heating schedules and/or heating settings to correctly reflect the desired heating times. Continue to monitor the underfloor heating system over the coming days to see if the issue has resolved.
- If the Heating Schedules are Correct: The thermostat is not impacted by incorrectly scheduled heating times. Check if the thermostat is in manual mode.
Is the thermostat in Manual Mode?
Navigate the thermostat’s settings to check if the thermostat is set to Manual Mode.
If yes, navigate the thermostat’s heating settings to confirm if a target temperature is set.
- If Manual Mode is On: The heat must be turned on and set to a target temperature manually. The thermostat will not automatically turn on or off to reach any scheduled temperatures.
- If the Target Temperature is Not Set: The thermostat will not heat in manual mode if there is no target temperature set. Set a target temperature and monitor the underfloor heating system over the coming days to see if the issue has resolved.
- If the Target Temperature is Set: Check that the target temperature is set higher than the current floor temperature. The floor will not energize if the target temperature is below the current floor temperature.
- If Manual Mode is Off: The issue is likely not with the programming or heat settings.
Check the floor temperature reading.
If the thermostat displays a temperature that does not match how the floor actually feels, the thermostat may not be activating because it thinks the floor has already reached the target temperature.
Is the floor sensor reading too high?
Check the temperature reading on the thermostat’s screen. If the floor temperature shown is higher than it should be (ex., is reading 90°F but the heating is off), this could be the result of improper wiring during installation.
Why is the thermostat reading an incorrect higher temperature?
There are 2 main issues that will cause the thermostat to sense a higher than actual temperature:
- Sensor Probe Placement: Installing the sensor probe bulb too close to the heating cable can cause the sensor to read a higher than actual temperature. During installation, the sensor probe bulb should be placed equidistant between 2 cable runs to achieve the most accurate temperature readings.
- Conduit Usage: Installing the sensor probe wire in the same conduit as the cold lead from the floor can cause interference causing the thermostat to incorrectly sense higher temperatures. During installation, the sensor probe wire should be placed in a separate conduit from the heater’s cold lead.
How do I adjust my thermostat to fix these errors?
To fix this, change the thermostat’s sensor application setting to activate based on the room temperature instead of the floor temperature. The thermostat will now disregard the floor sensor reading when determining when to activate the floor heating system.
Check how the floor heating system was installed.
The installation conditions of an underfloor heating system can affect the overall efficiency and performance.
Confirm the below with your installer and adjust your thermostat settings accordingly:
Was insulation installed over a concrete slab subfloor?
When installing floor heat over a concrete slab, it is highly recommended to use a layer of insulation between the subfloor and the heating system. This will help to redirect the heat upwards rather than letting it sink into the concrete slab.
Why does concrete slow heating times?
Concrete has a high thermal mass, meaning it absorbs a significant amount of heat before the finished floor begins to warm. Without insulation beneath the heating system, much of the energy is directed into the slab instead of the room, resulting in longer heat-up times.
Why does insulation matter when installing underfloor heating over concrete?
Insulation acts as a thermal barrier between the heating system and the concrete subfloor. This barrier will help the heating system to reflect heat upwards so that it does not sink into the subfloor. Because the heating system will no longer try to heat the concrete slab to equilibrium before heating upwards, the heat up times are greatly reduced.
How do I improve system performance?
There are 2 main ways to adjust the thermostat’s settings to increase the performance of a system installed directly over a concrete slab:
- Increase the Setback Temperature: The setback temperature setting is the minimum temperature that your heating system will continually maintain, even outside of regular programming. By increasing the setback temperature, you can ensure that the slab will always maintain a warmer temperature. Because the heating system will not be fighting to heat a cold slab first each time it turns on, heat will make its way upward into the room more quickly.
- Adjust the Heating Schedules: If you know that the room will take some extra time to achieve its target temperature, you can adjust your heating schedules to begin earlier than the time you would like the room to be at the target temperature. This will allow the system more time to “pre-heat” to the desired temperature.
When should I contact an electrician?
Contact an electrician if:
- The heating indicator is on, but the floor does not get warm,
- The thermostat’s heating settings/schedules are correct, and
- The floor temperature readings appear inaccurate.
If these checks have been completed and ruled out as a possible issue, contact an electrician to perform the remaining electrical troubleshooting tests.
Check the electrical system.
If the thermostat settings are correct and the underfloor heating system was installed properly but the floor still is not heating, electrical testing should be performed by a qualified electrician.
Is the thermostat wired correctly?
Remove the thermostat from the wall and ensure that the wiring into the thermostat is done correctly and securely. Incorrect wiring will cause the system to not function properly.
Is the correct voltage supplied?
While Warmup thermostat’s are all dual voltage, it is important to bring the correct voltage from the panel into the thermostat depending on the voltage of the heating cable.
If there is a 120V cable in the floor, the incoming voltage should be 120V. If there is a 240V cable in the floor, the incoming voltage should be 240V. If 120V is brought in to power a 240V cable, it will decrease the wattage output of the cable, thus increasing the time it takes a room to heat to the desired temperature.
Is the heating cable within its proper resistance range?
Using a digital multimeter, check the resistance of the heating cables. If the cable’s resistance is out of range, it indicates an issue with the heating cable.
What is considered out-of-range?
It is normal for a cable to be within +/- 5% of its given resistance. Anything outside of that range could indicate an issue with the heating cable.
For example:
- Cable: DCM-240-390
- Product Resistance: 147.7 Ω
- Acceptable Range (±5%): 140.3–155.1 Ω
A measurement outside of that range may indicate damage to the heating cable.
Each cable has its own resistance. Check the specifications for your heater model to confirm the correct resistance for your specific product.
Compare with original readings.
Compare the current readings of the heating cables to the readings that were taken when the system was first installed. A slight change is normal, however, if the readings are significantly different, it could indicate that the cables were damaged after the initial installation.
Does the heating cable need repair?
After your electrician performs the above tests, if it is determined that the heating cable is damaged, your electrician will need to perform a cable repair. Once the location of the break has been identified, follow the below video to repair the cable:
Cable repair kits can be ordered free of charge from our Warmupedia Shop.
Contact Warmup for further assistance.
If you are still experiencing issues with your heating system after troubleshooting with the steps above, please contact us to further assist.
We can be reached by email at ussales@warmup.com or by phone at (888) 927-6333.
