OWB to heat kiln?

xlogger · February 06, 2015, 06:59:53 AM

If anyone here uses their OWB to supply heat to their kiln I'd like to talk to them. I would like to build a box near my boiler and use it if possible. Please PM me so maybe we I might ask a few questions. Thanks, Ricky

beenthere · February 06, 2015, 10:00:46 AM

xlogger
Ask away... we're interested too. ;)

GeneWengert-WoodDoc · February 07, 2015, 12:05:07 AM

With an OWB, are you planning to use hot water or will you have steam. Hot water works, but steam is often better has it is hotter and provides for more energy transfer per foot of pipe. Hot oil is even better, but for some reason we do not see many hot oil boilers in the US or Canada. I have seen more in foreign countries...lower maintenance is a big advantage.

xlogger · February 07, 2015, 06:33:00 AM

I was hoping to use the hot water going threw a heat exchanger with a fan behind it for my heat source. I was thinking about building a small one maybe that would hold up to 12 foot slabs or lumber and about to 5-6 foot high that I could load with my forklift. Also put in a dehumidifier.
Some answers I was going to ask was probably more on the construction also. This would be my first kiln and was wondering about how much room extra for walk in to check on drying and maybe some extra room behind lumber so just in case I had some hand size slabs to add while the bigger load is drying.
I got a PM from Red Oak, he going to send me some info on his.
I've got an heat exchanger on my hot tub and was thinking the setup is close to use for a kiln with some thermostat to control the temp. Not sure how hot I can get it inside. My water is around the 180°.

GeneWengert-WoodDoc · February 07, 2015, 07:13:51 AM

Your idea is not impossible, but it is going to be tough. First, drying requires a lot of energy to evaporate the water. So, you will need more heat than you might be getting from this system you propose. For example, 1000 bf of lumber requires about 6 million BTUs.

I am not sure why you need a humidifier, as the wood is already providing about 4 gallons of water per 1 % MC loss per MBF.

A kiln is basically an insulated room with fans, heat exchangers, doors, etc. For safety, two exits are required. The fans sizes are easily calculated. In addition to the lumber pile, you need room on both sides for the air to move and for an operator to work. In a small kiln, it might be only 30". Once the moisture is evaporated, you need to get rid of it, usually by venting.

There are a lot of subtle design considerations for a kiln, so certainly use a standard design, rather than try to start from scratch. For example, NYLE sells plans for a kiln that uses a refrigeration trailer (reefer van). They have other small kiln plans.

xlogger · February 07, 2015, 07:20:57 AM

sorry dehumidifier. I changed it

red oaks lumber · February 07, 2015, 08:00:16 AM

iv'e been using my owb to supply heat for my kiln for over 10 yrs. i have a 200,000 btu heat exchanger which is plumbed using the hot water from my woodstove hanging from the ceiling in my kiln which holds 15,000 bf. using a wall therostat to control the temp, i have no problem finishing at 150 deg. even in the dead of winter when the kiln is changed,starting temp will be around 35 deg. 12 hours later it will be around 100 deg.
since switching to using only heat from my stove my kiln operating costs have dropped by 60%. the whole shop is heated from scraps the shop is creating everyday.

GeneWengert-WoodDoc · February 07, 2015, 08:42:09 AM

Red oaks...do you know your water temperature?

Southside · February 07, 2015, 09:52:46 AM

Subscribing

scsmith42 · February 07, 2015, 10:20:40 AM

FF member GA_Boy (Mark) used to heat his kiln by an OWB as I recall. I don't remember if it was steam or simply hot water though.

Hopefully he will chime in.

red oaks lumber · February 07, 2015, 12:24:46 PM

i run my water temp at the stove 195 deg with my set point and 190

GeneWengert-WoodDoc · February 07, 2015, 11:45:24 PM

The 195 F is much better than 180 F.

xlogger · February 08, 2015, 05:12:33 AM

With a click of a button I can get to 190°. Now I just need to come up with a building design and hope to get started. But when I start getting ready someone calls and wants something asap. I didn't know this retirement life was going to be so busy :D. I still think I would like to add a solar kiln also later.

GeneWengert-WoodDoc · February 08, 2015, 06:23:33 AM

My suggestion is that you visit a commercial kiln that is the same size as you want. This will give you design parameters. Including fan size and location, vent size, heat pipe location, and so on. Although you build your own insulated walls with insulation that can withstand the heat, a commercial kiln door is usually best for ease of opening, safety and long life. Repair is easy as well.

There are requirements for a kiln, such as two exits, both with handles on the inside. A couple of interior lights are a great idea. Vents can be troublesome when on the roof, so they are often on the front and back walls. Concrete is best if river rock instead of limestone. Fans need to be of the correct size, volume-wise and need to be reversed every two hours. Finally, a good control system to control temperature and RH is critical for best quality.

Note that the heating system is just one part of the kiln.

LeeB · February 08, 2015, 09:42:33 AM

Gene, why is river rock better than limestone aggregate?

dean herring · February 08, 2015, 10:16:08 AM

Is fan reversing done auto by kiln controls?

Den Socling · February 08, 2015, 11:53:56 AM

Lee, if you are drying something like Red Oak, the acid dissolves the limestone.

LeeB · February 08, 2015, 11:55:40 AM

Makes sense.

GeneWengert-WoodDoc · February 08, 2015, 11:28:07 PM

In the simple systems, a clock timer controls fan reversal.

Ga_Boy · February 09, 2015, 12:45:00 PM

I used a Heatmor Unit running at 190 to heat a kiln. The chamber was a 20 foot insulated shipping container. It worked well, the door seals on a shopping container are outstanding.

If you go this route, run your electrical cables outside the chamber as much as possible.

Let me know if you have a question.

Mark

Billikenfan · February 18, 2015, 02:37:39 PM

I use it to OWB. I have a shipping container that is insulated and stainless steel lined. The lining is important because the acid in the oak will eat regular metal. I heat it to 190-195. I have a 235k btu exchanger in the container. There are 2 side louvers that open when the humidity hits a certain level. Another door opens with a fan any bring in fresh air as the humidity is leaving. My boiler sucks a lot of wood when I put a fresh load in. But I can dry 2 cords or firewood in just 3-5 days depending on the split size.

Scott

beenthere · February 18, 2015, 03:25:45 PM

Scott
How many cords of firewood do you have to burn to dry 2 cords of firewood in 3-5 days?
What species are you putting in the kiln, and is it split?

Pics of a kiln load would be great.

thecfarm · February 18, 2015, 07:34:31 PM

Billikenfan,welcome to the forum.

Billikenfan · February 18, 2015, 08:48:01 PM

Thank you for the welcome. I'll get some pics when I unload it. I bought it from Mountain Firewood Kilns several years ago. It's hard to tell how much I burn because of what I burn. I burn all my splitter trash, sawmill slabs log cut offs, and the punky stuff to junky to sell. I would guess if I had all good wood it would take 1/3 to half a cord depending on weather. These zero Temps make a big difference.

Billikenfan · February 19, 2015, 10:27:29 PM

Here are a few pics. The basket with wood holds 2/3 of a cord. I put in 3 baskets at a time. The front gate on them swings so I can dump them out. The pictures are in my gallery.

Scott