Error 621 appears in the display of the CP plus panel – what should I do?
This error is displayed flashing during the first commissioning of the heater.
Warning 621 flashes because the heater is in a 15-minute lockout period.
Wait until the 15-minute lockout period is over. Please do not switch off the control panel during this period and do not interrupt the power supply.
As soon as the lockout period of the heater is over, the error is no longer blinking but permanently displayed.
Delete or acknowledge the error code:
Briefly press the rotary push button on the CP plus (the backlight will be activated when the button is pressed if the control panel was in standby mode)
Press the rotary pushbutton briefly again (malfunction / error is acknowledged by pressing it again)
The warning E 621 H is displayed constantly and appears again after the acknowledgement.
The room temperature sensor is not connected or is defective / the room temperature sensor cable is defective
Please see further information: https://www.truma.com/int/en/faq/fault-code-on-truma-cp-plus-control-panel.html