My Boiler Mate too is making a very loud hmming noise

I have just moved into a new property.

When I got the keys I turned the boiler off not realising it should always be left running as I did not move in immediately.

I have now switched it back on and it is humming very loudly (too loudly to leave it on). The green light is on. The dial is currently set on summer, the water is warming up but not the radiators, is this normal, I have never seen this system before?

What is the cause of the loud humming/buzzing noise and is it expensive to fix?

Thanks

You may have the same problem as here
https://gledhill-repairs.forumotion.net/t1406p15-new-member-with-questions#5106