Article Summary:
If your radiant system isn’t heating during a System Test and you get a T05 error, here are a few things you can try to troubleshoot.

To help make sure your system is set up and connected correctly, we created System Test, so you can easily check for any problems during setup, or anytime you need. Below are steps to help you if you get a T05 error during a system test.

How do I test my heating or cooling system?>

Wait a bit longer for the test result

Radiant underfloor heating can take a long time to heat up so it's recommended that you test your system for about 30 minutes. But every system and home heats differently, and the weather outside may also mean it will take longer for your system to heat up, so it may be harder to recognize when heating is taking place. The System Test will run for 35 minutes before automatically stopping.

A Nest Thermostat heating test will automatically stop after 35 minutes to prevent inadvertent energy waste. So if it takes more than half an hour for your system to heat your home noticeably, try running another heating test right away. Select KEEP TESTING on the thermostat. Since your system should already be warmed up, you should notice an increased ambient temperature during the second test.

Reseat the wires

Remove the Nest Thermostat display and double check that the wires are firmly seated in the connectors. Trimming and stripping the ends of the wires can be helpful to ensure that they are making solid contact.

CAUTION: It's important to protect your thermostat and your system. Turn off power to your system and thermostat at the fuse box before exposing or adjusting any wiring.

If the above suggestions don't resolve the issue, there are additional strategies to try in the Troubleshooting tool. You can also contact a Nest Pro using our online finder.