The condensation trap can get choked with grit (a by-product of the products of combustion). Is it full to the brim? It should only have 'some' condensate in it.
CMac
November 2010
What boiler is it...
Gary
November 2010
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.