My homemade heating system for the shop.

[WZ JUNK]

Propane has been expensive but I have a cheap source of firewood.  I wanted an outside wood furnace for safety reasons and I have always liked hot water heat.   I built an outside furnace for heating water out of a Shrader Wood stove that was given to me.   Last year I built the first generation model.  I used a cast iron radiator, that many of you have seen in use in older buildings with hot water heat, for my heating coil inside the firebox of the stove.  Inside the shop I used a car radiator and a large squirrel cage fan off of a gas furnace.  This system worked okay but it used a lot of wood and took a lot of my time keeping it going.  

This year I added an external water jacket by fabricating 7 shallow tanks that surround the furnace.  The water circulates through the tanks and then into the fire box through the cast iron coil and then into the shop.  I use a Bell and Gosset recirculating pump that is normally used for a hot water circulating system in a house.  The new heat exchanger inside is a coil off of a commercial freezer.  I bought it from a junk man (no relation) for $20 and it included the fans.  The water side of the system is vented to the atmosphere and does not build pressure.  There is a heat and pressure relief valve that will dump the water to a storage tank if there is a problem.  Once I set the system up I built an insulated box around the unit.  The insulation came from dumpster diving at a construction site where they were reroofing a flat roof building.  Eventually I plan to surround the whole thing with a metal box.  In addition I am going to build a back up power supply system using a 12 volt car battery and a convertor to power the system should I lose regular electrical power.  This will run the system until it cools down.

To operate the system you build a fire in the wood stove.  The stove has a forced draft that is controlled by the temperature of the water.  When the water temperature is less that 155 degrees F the fan is on and when the temperature rises above 165 degrees it shuts off.  I found this temperature to work best for me.  Inside there is a thermostat that controls the fan motors on the heat exchanger.  You set the temperature you want the shop to be just like you do your thermostat in your house.

I was pleasantly surprised  at how much better it works this year.  Originally I had to be careful not to make to large a fire as I can easily overheat the water.  

In addition to the wood I also burn waste oil in this system.  I get some heat from burning the oil and I get rid of my oil.  I am going to do some more work on this system.  It is the round tank just above the front of the furnace.  The oil is metered in through a needle valve and drips on a large steel plate in the top of the firebox.

I will continue to modify and improve this system.  I am open to any suggestions for improvements and I will answer any questions you may have.

John

[enjenjo]

Looks great John. How warm do you keep it?

[WZ JUNK]

Looks great John. How warm do you keep it?

About 70 to 75 degrees as I have been spraying some primer lately.  It has been in the mid teens most nights lately and just into the 20's during the day.   I let it die down at night and then fire it up in the morning as I do not need to keep the shop heated at night.  Most of the time the shop is still about 50 degrees in the morning.  It takes just a few minuets to get the water hot.  I had to put a limit switch on the water side to turn on the inside heat exchanger fans if the water gets to 190 to keep the water temperature down.  This only happens occasionally.  Most of the time the water stay around 160 to 180 F.   I am still tinkering with it but it is fun to have a different kind of project.

John