I had a central heating system fitted last year with a combi boiler, no problems until this evening when I heard a whirring /buzzing noise louder than usual in the airing cupboard where the boiler is. When i opened the door I could smell a faint burnt smell like burnt plastic and the noise was coming not from the actual boiler but the plastic box on the wall (not sure if this is a pump or motor...?? I have no knowledge of heating systems whatsoever!! Have turned it all off at the wall, but just wondering is it safe to switch it on again in the morning and just put up with the noise until i can get it serviced? Think I'll freeze otherwise!!