I hope you find a solution.

i have a nibe f2040 12 which was installed in 2015.

three years ago it started to shut itself down when the outside temp fell below freezing. The error was BT301 “comms error slave 1”.

i reset the alarm and if the temp had climbed above freezing the pump would run again until the next cold spell. If it was still below freezing the pump would restart and run through the heating cycle, the hot water cycle and then start the defrost cycle. After a couple of minutes the alarm would go with the same error message.

i called a local recommended NIBE firm (my installer was a family firm who had since retired). They came out, needless to say the fault was not present when they called, and they could not replicate it so couldnt fix it.

the pump ran ok all through the next summer until freezing conditions occured again. Same error!

and again last summer, until this latest cold snap came. Same problem. In the meantime i had contacted nibe technical dept who suggested it could be an error on PWB1 or with the comms cable. This time i contacted another local nibe engineer who came out when the weather was not freezing. Needless to say he could find no problem. He suggested that the fan motor might be struggling, but recommended i recontact nibe to get an engineer out. However they will not attend fir breakdowns or diagnosis, as i am out of warranty.

i know from the time that the pump runs when i reset the alarm that there is something not right with the defrost cycle (which is pretty obvious!) but no one seems to know what.

has anyone else experienced this and can anyone help please