Hi all I have a warm flow boiler with a Riello RDB1 90-120 burner It started to randomly lockout some time ago and an engineer changed the photocell and solenoid without success I was told by the local plumbing wholesalers they had been supplying a lot of pumps recently for Riello burners as something about the oil being supplied in our area ( north highlands ) was making them fail prematurely. I changed the pump with no result still randomly locking out sometimes after a few minutes or an hour or so. I was advised to add an oil conditioner treatment so got some and added it to the tank and within a short time the lockout problem disappeared. Anyone know what this is? Could it be just the oil or possibly a nozzle or fire valve problem ? I have had another fill since and tried it without conditioner in the oil and the lockout problem came back then went away as soon as I added conditioner.