Noisy boiler.

[maggie01]

When I turn the thermostat up on the boiler, after about 10mins when it has reached the temperature, is starts to make a loud humming noise. After a short while, it goes quiet.

This happens everytime I turn the thermostat up.

Any ideas please.

[KARL]

Does the noise resemble that which an electric kettle makes just as it is coming to the boil ? If that is the case then there may be a localised area in the waterway within the boiler that reaches a similarly high temperature. There are scores of different types of boilers in use and much depends on the arrangement withing your particular boiler and also the plumbing arrangements. If you know anyone with a bit of knowledge it is best to ask him/her to witness the event and do a few carefully aimed tests to eliminate some possible explanations until the precise reason is identified.