We have inherited this Dominion Radiator and Boiler Co Ltd, wood fired boiler but know little to nothing about it. We would like to use it for a hot tub heater out in the back country cabin. Can anyone give us any information about how to use it and set it up for such a use? There is a grate between the firebox and ?boiler that we are unsure of. Please see photos. Anything would be useful - thank you.