Wood fired kiln options

True North · November 01, 2009, 07:59:18 PM

We just put in an outdoor boiler in our woodshed and it occured to me that I could add on to the shed to make a kiln heated by the boiler. Does any know the best way to set it up?

kelLOGg · November 02, 2009, 04:50:37 AM

Check with Solidwoods - he's done it. A search will reveal info.
Bob

solidwoods · November 02, 2009, 07:42:21 AM

I have 2 kilns in the wood shop. In the winter, I vent into the shop for some extra heat (most of what I dry is 15%mc so excess humidity isn't a prob).

When not in use I use the kiln for a finishing room. I use water based finish so the heated room is handy.

I'm building another work shed and it will have a 10' x 50' kiln in it so I'll move the other kilns out of the shop.
Since the walls aren't load bearing the new kiln has 12" wide wall trusses from 1x3s.
I'll fill the walls with shredded Styrofoam recycled from waste and run through a wood chipper. Also these type of walls don't need 2x12s and are less of a thermal wick than solid wood studs.
The point is really put the insulation to the box.

The new kiln will be in a 50'x50' bldg. I've designed it to be on the south wall. On the outside of the south wall is a full length green house. The new kiln will vent into the green house.

I've also used 1.5" thick styro recycled from a chicken house tear down. The crew was glad to not have to take it to the pay landfill, I was glad because styro is expensive.

For a kiln controller I use the Pola egg discloser. It has 2 thermocouples input. 1 is the dry bulb and the other has a cotton sock on it , set into a cup of water to input wet bulb info. It also has 3 relays on it to control heat, vent, and humidity.
Heat is controlled by a Taco 2 way valve, 24vdc.
Vent is relay to a small fan.
Humidity is relay to a 110vac water valve which wets a large cotton towel in the kiln and raises the humidity.

For heat exchange you can use allot of things. 3/4" steel pipe, salvaged heat exchanger tube from an air conditioner split unit, or copper tubing.
For copper tube I drill out a pex barb to slip fit the copper tube inside and solder it. Now the end has a barb fitting to fit the pex .

The kilns I use will run off the 1 main pump on the boiler, but I installed a pump for the kilns because I had one on hand. The pump does have a positive effect for more heat which I mostly use for initial start up.

Other uses I do are:
My wife dog grooms, I purchased a tube type heat exchanger to make hot water for the dog bathing water. This eliminated the elec. hot water heater.

Under the upstairs bath tub which is a cast iron corner tub with a wet wall, I ran 150' of 3/8" copper tube. Turn on the valve and you have a hot bath tub. On the wet wall I installed full length doors so they can be opened to let the heat out as a room heater. Also handy in spring / fall to avoid shower curtain mildew and it drys towels.

For a shop heater I run hot water through a a/c unit condenser unit. Take out the compressor, make a manifold to feed the coils, leave on the relay and fan. Just turn on the valve and plug in the fan. Thats going out soon though because its noisy. next will be 3/4" pipe on the ceiling as an exchanger with ceiling fans (I have a vaulted ceiling so it holds allot of air space/hot air)

jim

Den Socling · November 02, 2009, 09:42:47 AM

Jim,

Good post! I was going to suggest a 3-way diverter valve for proportional heat control but why bother?

Den

solidwoods · November 02, 2009, 01:18:19 PM

Howdy.
I may be talking Apples/Oranges.
But with hot water.
A 2 way valve lets hot water into a circuit, just off/on.
A 3 way valve lets hot water into a circuit when its on but when its off it sends the hot water back to the return circuit.
The 3 ways are needed for a circuit where if the rtn. line were off (as with a 2 way) the rtn. line would be in danger from freezing.
I have my house on the end of my hot water circuit so if I used a 2 way, the line to the house could freeze. But the kiln is in a heated bldg. so its rtn line can't freeze.

My total water line is 300' long.

My circuit is:
Heater to shop, in the shop has 2 kiln circuits, 2 shop heater circuits (hand valve), and a domestic hot water heater (continuous on) it then is in the ditch with the water feed from the well so the pipe won't freeze, then through the well box to heat it then the ditch with the water feed to the house (no freeze ) then to the floors of the house also a circuit to the tub.
jim

Den Socling · November 02, 2009, 02:40:37 PM

Jim,

I always use two closed loops. A heat exchanger is between the boiler water and the kiln water. That way you don't need to worry about freezing.

Den

red oaks lumber · November 02, 2009, 06:31:15 PM

i heat my kiln with 3 =100,000 btu heat exchangers from my outside boiler, i run my water temp on the stove at 195 deg. can easily keep the kiln at 140 deg.