I have a combi boiler which has been going great it cut out yesterday and then the digital display and power went off. I spotted the blown fuse which I have replaced but it keeps fusing any ideas?

Is this a fuse in the house panel, or at the furnace? Is this fuse for line voltage,120 volts, or 24 volt control?

There must be a short in the wiring or a defective component that is causing the fuse to blow.

Really need more detail to be able to help direct you in the right direction.

The fuse is a 24volt one within the boiler there are two fuses on the circuit board little clear ones two watt I think. Only one blows every time you try to turn the heating or water on. Its fine with the power back to the main light and the digital clock is on again. Which component within the boiler would case the problem?

Can be any relay coil related to the water or the heat. I suspect the short is in the wiring to these components.Trace the wiring the fuse is connected to looking for a pinched wire/cable, a loose strand of wire touching metal, or some other problem that can short out the wiring. If the wiring seems fine, then you will need to disconnect each relay and test each use a ohm meter looking for that shorted unit.