i have apollo 15/30 type wall mounted boiler and have an electric (i think ) fault in the system ..at first it blew the main fuse after boiler was on an hour after the heating switched off and the boiler ran on for 20 min...then several time it blew after 5 minutes of switching heating on..ive replaced the thermostat and acuatator ..(usual suspects )and still blows the main 5amp fuse/...the acuator box fuse (5amp) and boiler fuse (5 amp ) (switch just below the boiler ) doesnt blow...just the mains one ...could it be the main pump either internaly leaking into the pump /...i can understand the fuse going with the pump hot..but it now blows with the pump cold after 5mins on..the pump seems to be working during that 5 mins ...can the pump be the problem.. ?any answers please this driving me nuts !..all other electrics are fine