What it means
Vaillant also lists a lock-out by the power company lasting more than three hours as a cause, on systems where the supplier can switch the heat pump off, and says that lock-out time must be under three hours.
What to check, in order
- Check the breakers
Look at your consumer unit and any separate supply for the heat pump. A defective fuse is the first cause Vaillant lists, and its troubleshooting table says to switch the building's power supply back on if it is off.
- Reset once
Then press the reset button on the control module.
- Leave a tripping breaker off
If a breaker trips again, leave it off and call your installer.
When to call your installer
Your installer will check the fuse, the electrical connections and the voltage at the heat pump's power connection, and that the compressor or off-peak supply is connected.
Quick answers
What does the Vaillant aroTHERM F1117 error code mean?
The heat pump has found a problem with the power supply to the compressor, such as a blown fuse, low mains voltage or a supply that is not connected. Vaillant also lists a lock-out by the power company lasting more than three hours as a cause, on systems where the supplier can switch the heat pump off, and says that lock-out time must be under three hours.
Can I fix Vaillant aroTHERM F1117 myself?
Easy (about 10 minutes). Start with: check the breakers; reset once; leave a tripping breaker off. Your installer will check the fuse, the electrical connections and the voltage at the heat pump's power connection, and that the compressor or off-peak supply is connected.
Is Vaillant aroTHERM F1117 worth repairing?
Worth fixing. A tripped breaker or a supply interruption can be the whole story, so a check and reset may be all it needs. Wiring or voltage problems need an engineer.
Checked against
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.