OIL FIRED BOILER TRIPS RCD ON FIRING?

I have a Worcester Danesmoor 15/19 oil fired boiler with a Nu-way B01-S35-O-001 burner fitted. Each time the boiler fires it trips my RCD. I have linked out the stat., dissconected the pump, swapped the Satronic, but the fault still remains. HELP! its cold and snow is on the way!