I don't need another project right now but this has been in the background for several months and I figure it's time to post about it. I'm trying to clean up and get rid of stuff I will never use. This project is based on a heater that I don't want to scrap.
I bought it 30+ years ago for a project and it sadly has spent the last 20 or so outside under cover. There is some surface rust. Today I dragged it out from under the deck and put it on a cart.
It is a 75000 btu navy engine coolant heater. It runs on diesel and 24 volts and I did run it way back then to test it.
I ve spent some time over the last few days looking for the manual which I do have somewhere. I did find the box of spare parts. It's a metal box about 15" x 15" x 25" filled to the top with spares all in sealed packages. This thing is mil spec and it was/is quite fancy. It even had a pyrometer to monitor the flame. (gotta find that manual)
The plan is to replace the oil burner with a modern style pellet burner. It will take about 10 lbs of pellets per hour to replace the oil.
If you take out the oil burner the rest of it is a 1/8" thick walled stainless steel flash boiler and a 24 volt recirc pump and a 24v blower.
I've looked at a lot of pellet stoves and the nice ones have self ignition and are self extinguishing (you turn off the pellet supply), automatic pellet feed etc and an oxygen sensor so you can control the combustion. All fun little mechanisms to build.
What prompted thinking about this now it that last month an electronics magazine published an article on building an interface for a Bosch Lambda sensor (oxygen sensor). If I waited a few years that would be obsolete and I would have to design my own so I ordered all the parts for the sensor system. I got the Bosch sensor itself on ebay on the weekend. It has been shipped and the bulk of the electronic components arrived here this morning.
It will take a while to design it and collect the parts at reasonable prices. I need to make or buy one or more small augers. 2 1/2"-3" to move the pellets. Probably drive them with stepping motors. What seems to be the best ignitor for the pellets is a jet of very hot air. Then you don't have a heating element buried in the fire.
In operation a microcontroller will run the thing based on measuring the oxygen in the exhaust gases (and temperature) and adjusting the fan speed to provide the correct air mixture. It will also look at water temperature and flow so nothing overheats etc.
First step will be to get some penetrating oil on all the fasteners.