Have an issue where the 3A fuse on the socket that feeds the pump and heating controller unit keeps blowing when the boiler kicks in. Pump replaced for brand new Grundfos 2 weeks ago - its the right way up, etc. Have some rust and larger iron oxide lumps in the system, but have removed pump and rinsed through to remove detritus.

Have cut and re-terminated the electrical connections from mains to pump, as well as using hair dryer to ensure no water ingress.

Running out of ideas....Any help appreciated?

H2O, January 2009

Is the boiler a back boiler.If it is it could be that if you havent had it serviced for a bit the flames have started to burn incorrectly and have burnt through the wiring behind the fire.Evertime you put the boiler back on it will pop the fuse.DONT be tempted to put a bigger sized fuse in as it will go with a right old bang..If its not a back boiler then an electrical part other than the pump must be faulty,but i am guessing that your boiler is on its way to sooting up.

Tony S, January 2009