What causing a crackling noise in all radiators and boile when heating is on?
IT could be that where a pipe goes through a wall or up through the floor a pipe is a tight fit and the expansion and contraction of the pipework makes the noise, sometimes noise is generated in the pipework due to what is called cavitation which is caused by the water flowing through the pipes to fast next time it happens try adjusting the pump speed most pump have a two speed switch on them
