This might be a job for Piglet John but maybe someone else will know.
We just moved into our new house a month ago. Two days ago, we heard this weird buzzing/humming noise coming from the area in which we think the pump for the central heating is located. We aren't sure though- it is a heating oil system which we have never had before and we have little clue where the works are to be found- there is a small unit in the kitchen in a cupboard where the timer is, with a red tank thing with a valve on it and a pressure gauge but that is all we can see.
When we turned off the heat, the noise stopped. It seemed to all run fine in the morning and from 4pm to about 7.30 pm yesterday and then the humming/buzzing started again at exactly the same time as before.
Any ideas?