Please check the Tooltips of each to see if their Input and Output Amounts are matching. Boilers really only explode if you either run out of Water, produce far more heat than the Boiler can output Steam for, or if the Steam cannot go anywhere.
The Fuel you use in a Burning Box has absolutely NOTHING to do with if a Boiler explodes or not.
If you see your Boiler is about to explode, the worst case would be that you quickly remove the Burning Box itself, in order to prevent the Heat from getting into the Boiler, in which case your entire Setup is wrong and not the Fuel you use, since Fuel does NOT influence the amount of Output.