How to Test the GFCI and Fix a Ground Fault Error on a Warmup Thermostat
Most Warmup floor heating thermostats have a built-in GFCI (ground-fault circuit interrupter) that cuts power to the heating if it detects current leaking to ground. To test it, make sure the floor is heating, then press the thermostat’s GFCI test tab or button. A “Ground Fault” message means the GFCI is working. Clear the message to return to the home screen. If a Ground Fault error appears when you haven’t pressed the test button, or the GFCI keeps tripping, the system needs troubleshooting.
What is the GFCI on a floor heating thermostat?
A GFCI is a safety device that compares the current going out to the heater with the current coming back. If the difference is more than about 5 milliamps (mA), current is leaking to ground, and the GFCI shuts off power to the floor to protect you from electric shock.
- Class A protection. The GFCI in Warmup thermostats is Class A, which trips at about 5 mA. This is a very sensitive trip level required by UL.
- How to tell if your thermostat has one. If your thermostat has a clear tab on the bottom, or the words “Test Monthly,” it has a built-in GFCI.
- No GFCI breaker needed. Because the thermostat already has a GFCI, the floor heating circuit does not need a GFCI breaker at the electrical panel. Two GFCIs on one circuit can cause nuisance tripping.
Do I need GFCI protection for floor heating?
Under the US National Electrical Code (NEC 424.44), floor heating cables installed in bathrooms, kitchens, and hydromassage tub, spa, and hot tub areas must have GFCI protection. A Warmup thermostat with a built-in GFCI meets this requirement on its own. Always follow your local electrical code, which may differ.
How do I test the GFCI on my thermostat?
Testing the GFCI confirms that it will cut power if a ground fault happens. Warmup recommends testing it monthly, and a test may also be required during an electrical inspection.
- Make sure the floor is heating. The thermostat must be sending power to the floor for the test to work. This means the target temperature is higher than the current temperature, and the heating indicator is showing. If the floor isn’t heating, temporarily raise the temperature.
- Press the GFCI test tab or button. On most models, push the clear tab on the bottom of the thermostat. On the EZPT, press the Test button.
- Check for the Ground Fault message. A “Ground Fault” screen means the GFCI tripped and is working correctly.
- Clear the message. On the 7iE, 6iE, 4iE, and 3iE, press and hold the screen for 3 seconds. On the Terra, press and hold X. On the EZPT, press Reset. The thermostat returns to the home screen.
What does a Ground Fault error mean?
It depends on whether you pressed the test button.
- You pressed the test button. There is no need to worry. The Ground Fault message is the expected result of a GFCI test, even if the screen turns red or tells you to call Warmup. Clear the message and the thermostat returns to normal.
- You did not press the test button. The thermostat has detected current leaking to ground. This can mean a wiring issue or damage to the heating cable or mat. Follow the steps below.
What should I do if I get a Ground Fault error without testing?
- Power cycle the thermostat. Turn the power off at the circuit breaker, then turn it back on. This often clears the error.
- Check the wiring. If the error comes back, have an electrician confirm the floor heating is on a dedicated circuit with no GFCI breaker at the panel.
- Test the heater’s resistance. Your electrician should use a digital multimeter set to the 200-ohm scale to measure the heater’s resistance. They will need the line-to-line reading and both line-to-ground readings.
- Compare the readings. Check the readings against the resistance listed for your heater model in the installation manual. A reading more than 5% outside that range points to a problem with the heater.
- Contact Warmup. Have your heater’s part number and resistance readings ready, then contact Warmup for additional guidance.
See how to test your heating cables for more detail.
Why is my thermostat showing a Ground Fault error after years of working?
Floor heating mats and cables are built to last, with no moving parts and no liquids to leak or freeze. A Ground Fault error after years of normal use usually means the cable was damaged by work in the room, such as:
- Trim or baseboard work
- Tile repair or replacement
- Grout cleaning or removal
- Installing doorstops or fixed furniture
Sometimes small damage during installation doesn’t show up until a few weeks or months of use, when it appears as a break or ground leak. Power cycle the thermostat first. If the error comes back, gather your heater’s part number and resistance readings and contact Warmup.
What if nothing happens when I press the GFCI test button?
First, make sure the thermostat is sending power to the floor. The test only works while the floor is heating, so the target temperature must be higher than the current temperature and the heating indicator must be showing. If the floor is heating and the test still does nothing, contact Warmup for technical help.
Why does my GFCI keep tripping?
If the GFCI trips repeatedly but your heater’s resistance readings are normal, the cause is usually “nuisance tripping.” Because a Class A GFCI is so sensitive, electrical noise on the circuit can trip it. The most common causes are:
| Cause | What’s happening | How to fix it |
|---|---|---|
| Two GFCIs on one circuit | The thermostat and the breaker both have a GFCI. | Use a standard (non-GFCI) breaker, since the thermostat already has a GFCI. If the system must stay on a GFCI breaker, contact Warmup to request a non-GFCI back for your thermostat. |
| Shared circuit | Other devices on the same circuit, especially ones with their own GFCI, cause noise on the line. | Put the floor heating on its own dedicated circuit breaker. |
| 240V neutral bus bar | On 240V circuits, breakers are often grouped together, and GFCI breakers share one neutral bus bar. | Move the 240V breaker to a more isolated spot on the panel, or connect its neutral wire (for GFCI breakers) to the other neutral bus bar on its own. |
Why does my thermostat trip at the same temperature every time?
The heater may have been cut during installation. A heating mat or cable’s resistance is set by its length. Shortening it raises the resistance and the temperature. The cable can run slightly hotter for a while, but this strains the end splice, so the thermostat trips and the heater can eventually fail. Never cut a Warmup heating cable. Ask your installer to test the heater’s resistance and compare it with the values in the installation manual.
Other frequently asked questions
How often should I test my thermostat’s GFCI?
Warmup recommends testing the GFCI once a month. A test may also be required during an electrical inspection.
Is it safe to use my floor heating after a Ground Fault error?
After a test, yes. Clear the message and use the floor as normal. If the error appeared without a test, the GFCI has cut power for safety. Don’t keep resetting it. Have an electrician check the wiring and test the heater’s resistance.
Can I reset a GFCI that keeps tripping?
You can clear the error, but if it keeps coming back, find the cause. Check for a second GFCI on the circuit, a shared circuit, or damage to the heater, using the steps in the Why does my GFCI keep tripping? section.
Do I need a GFCI breaker for my Warmup thermostat?
No. Warmup thermostats with a built-in GFCI do not need a GFCI breaker. Use a standard breaker on a dedicated circuit to avoid nuisance tripping.
Choose your product
How do I test the GFCI on the 7iE thermostat?
To test the GFCI on a Warmup 7iE Smart Matter Thermostat, make sure the heating indicator is showing, then push up the clear tab on the bottom left of the thermostat. A red “Ground Fault Detected” screen means the test worked. Press and hold anywhere on the screen for 3 seconds to clear it.
Steps to test the GFCI on the 7iE
- Turn the heating on. Check for the heating indicator to the left of the temperature on the home screen. If it isn’t showing, temporarily override the temperature to turn the heating on.
- Press the test tab. Push the clear tab in the bottom left corner up into the thermostat and hold it briefly.
- Check the result. A red screen reading “Ground Fault Detected” means the GFCI is working.
- Clear the error. Press and hold anywhere on the screen for 3 seconds. The thermostat returns to the home screen.
What if the Ground Fault Detected screen won’t clear on the 7iE?
Remove the faceplate and reconnect it to reset the thermostat. If the error is still showing, contact Warmup.
Video: how to test the GFCI on the 7iE
Watch the video to see each step on the 7iE. For more, see the 7iE instructional video playlist on YouTube.
How do I test the GFCI on the Terra thermostat?
To test the GFCI on a Warmup Terra WiFi Thermostat, make sure the floor is heating, then press the clear tab on the bottom of the thermostat. A GFCI trip error on the screen means the test worked. Press and hold the X button to clear it.
Steps to test the GFCI on the Terra
- Turn the heating on. Make sure the Terra is heating the floor. If it isn’t, temporarily raise the target temperature.
- Press the test tab. Press the clear tab on the bottom of the thermostat.
- Check the result. A GFCI trip error appears on the screen, which means the GFCI is working.
- Clear the error. Press and hold the X button. The thermostat returns to the home screen.
Video: how to test the GFCI on the Terra
Watch the video to see each step on the Terra. For more, see the Warmup YouTube channel.
How do I test the GFCI on the EZPT thermostat?
To test the GFCI on the Warmup EZPT Programmable Thermostat, make sure the heating indicator is showing, then press and briefly hold the Test button on the top right of the thermostat. A “Ground Fault Detected” screen means the test worked. Press the Reset button on the top left to clear it.
Steps to test the GFCI on the EZPT
- Turn the heating on. Check for the heating indicator under the time, near the top left of the screen. If it isn’t showing, temporarily override the temperature to turn the heating on.
- Press Test. Press and briefly hold the Test button in the top right corner of the thermostat.
- Check the result. A screen reading “Ground Fault Detected” means the GFCI is working.
- Clear the error. Press the Reset button on the top left of the thermostat. The thermostat returns to the home screen.
What if the Ground Fault Detected screen won’t clear on the EZPT?
Remove the faceplate and reconnect it to reset the thermostat. If the error is still showing, contact Warmup.
Video: how to test the GFCI on the EZPT
Watch the video to see each step on the EZPT. For more, see the EZPT instructional video playlist on YouTube.
How do I test the GFCI on the 6iE thermostat?
To test the GFCI on the Warmup 6iE Smart Thermostat, make sure the heating indicator is showing, then push up the clear tab on the bottom left of the thermostat. A red “Ground Fault Detected” screen means the test worked. Press and hold anywhere on the screen for 3 seconds to clear it.
Steps to test the GFCI on the 6iE
- Turn the heating on. Check for the heating indicator to the left of the temperature on the home screen. If it isn’t showing, temporarily override the temperature to turn the heating on.
- Press the test tab. Push the clear tab in the bottom left corner up into the thermostat and hold it briefly.
- Check the result. A red screen reading “Ground Fault Detected” means the GFCI is working.
- Clear the error. Press and hold anywhere on the screen for 3 seconds. The thermostat returns to the home screen.
What if the Ground Fault Detected screen won’t clear on the 6iE?
Remove the faceplate and reconnect it to reset the thermostat. If the error is still showing, contact Warmup.
Video: how to test the GFCI on the 6iE
Watch the video to see each step on the 6iE. For more, see the Warmup YouTube channel.
How do I test the GFCI on the 4iE thermostat?
To test the GFCI on the Warmup 4iE Smart WiFi Thermostat, make sure the floor is heating, then press the clear Test Monthly tab on the bottom of the thermostat. A red Ground Fault Error screen that tells you to call Warmup means the test worked. Press and hold the screen for 3 seconds to clear it.
Steps to test the GFCI on the 4iE
- Turn the heating on. The target temperature must be higher than the current temperature. On the large temperature display, a triangle heating indicator appears between °F/°C and Floor/Air, to the right of the large number in the center.
- Press the test tab. Push the clear Test Monthly tab on the bottom of the thermostat.
- Check the result. The screen turns red and shows a Ground Fault Error message telling you to call Warmup. This is the expected result of a test and means the GFCI is working.
- Clear the error. Press and hold the screen for 3 seconds. The thermostat returns to the home screen.
What if the Ground Fault Error screen won’t clear on the 4iE?
Remove the faceplate and reconnect it to reset the thermostat. If the error is still showing, contact Warmup.
Video: how to test the GFCI on the 4iE
Watch the video to see each step on the 4iE. For more, see the Warmup YouTube channel.
How do I test the GFCI on the 3iE thermostat?
To test the GFCI on the Warmup 3iE Energy-Monitoring Thermostat, make sure the floor is heating, then press the clear Test Monthly tab on the bottom of the thermostat. A Ground Fault Error message means the test worked. Press and hold the screen for 3 seconds to clear it.
Steps to test the GFCI on the 3iE
- Turn the heating on. The target temperature must be higher than the current temperature and the heating indicator must be showing.
- Press the test tab. Push the clear Test Monthly tab in the bottom of the thermostat.
- Check the result. A Ground Fault Error message means the GFCI is working.
- Clear the error. Press and hold the screen for 3 seconds. The thermostat returns to the home screen.
What if the Ground Fault Error screen won’t clear on the 3iE?
Remove the faceplate and reconnect it to reset the thermostat. If the error is still showing, contact Warmup.
If the GFCI on a UCCG thermostat trips without you pressing the Test Monthly button, the system is detecting a ground fault error. Find the model number on the heater under your floor and have an electrician, ideally the one who installed it, take the line-to-line and both line-to-ground resistance readings, then contact Warmup for a diagnosis.
The UCCG is no longer sold. Any current Warmup thermostat can replace it.
If the GFCI on a TH115 thermostat trips without you pressing the Test Monthly button, the system is detecting a ground fault error. Find the model number on the heater under your floor and have an electrician, ideally the one who installed it, take the line-to-line and both line-to-ground resistance readings, then contact Warmup for a diagnosis.
The TH115 is no longer sold. Any current Warmup thermostat can replace it.