21. Error message "check external security" Setsys Evolution.

A device safety device has tripped to prevent heating.
1. Flow of water that is too low. (prerequisite: 2 l / min 3 bar)
2. Error on the direction of water flow.
3. Defective water valve.
4. The thermal switch on the furnace body has tripped because the water temperature is too hot.
Contact the support department to assist you in troubleshooting.