Just had a combi heating system installed,worcester28sii,the property is a bungalow and the boiler has been istalled in the loft space with all the pipework coming down from the loft to the rads.Everything runs ok but sometimes the pipes that run down the walls seem to be making a humming noise as though the pump in the boiler is running to fast and is circulating the water in the system to fast.Would this have this affect and if so could I turn the pump down.