your main heat exchanger is blocked or partially blocked and will need to be replaced, this normally occurs when your system has become scaled or sludged up, so you will also need to have your system chemically flushed (power flushed) and treated. If you only replaced the heat exchanger and dont flush expect to get a very short life from the next heat exchanger. Also all the scale & sludge will be damaging your entire heating system not just your boiler and costing you in efficieny, it may cost up to £1000 to right the whole lot but well worth it.
Make sure to get a good recommendation from someone to get this job done right, lots or messers out there not flushing correctly (but still charging for it)
T, May 2008
