Hi I'm hoping someone can help with a problem I've had since November 20. I got a new circuit board fitted to my gas boiler and since then have had a loud droning/humming noise all around the house. Had engineer back 3 times and he says nothing wrong. Called water suppliers and they have checked water and say its fine although pressure was high. Got a pressure reducing valve and the noise still continues. Have bled radiators checked toilet and still the house hums. Switched power off and can still hear it. HELP!