I know you wood burning purists are probably not going to like this post but that's OK. I travel out every week and I am gone for three days and my wife is not willing to load the boiler. I got tired of coming back to my system at 120 degrees and spend an entire load of wood getting it back up to temp again. I only have 500 gallons of storage in my basement and my EKO is in an outbuilding so it doesn't last long when I leave. I have cut my propane use way down but still buy about 500 gallons a year. I was wanting a new project to have some fun with so I started researching waste oil heaters and have successfully converted a Beckett AFG fuel oil burner to run waste oil with some parts from CK burners.com and parts from McMaster carr. I then built an exact copy of the lower door of my EKO and cut a hole in it to mount the boiler on. I removed the lower U bricks and added some fire brick against the back and side walls for extra protection. I have 1000 gallons of free oil on hand. Last night I fired it up for the first time for about 45 minutes. It only raised the water temp from 75 to 111 degrees. I still have to integrate all the controls into the EKO boiler using some DPDT switches and relays. My plan is to burn wood when I am home then simply lift the door off and slide on the waste oil door and switch it on. Then remove the waste oil door when I return. Shouldn't take any long than starting a fire with the boiler cold and feeding it up to temp plus it saves me 3 days of propane a week. My biggest concern is heat transfer efficiency.