Wood stove Heat thru EXISTING DUCTS

[ridelikethewind]

Has anyone ever tried this with their wood stove?

See my pic.

I have a 55 gallon drum as a wood stove in the basement (not the best place for it I know, but that's another story).

The stove's firebox INCOMING vent is from the outside cold attic air and is piped down from the attic. So there is no cold air coming from the windows and this helps the draft.

I am going to build a metal box that sits on top of the stove with the same gauge metal.

This box will be vented completely separate and airtight from the rest of the stoves combustion gases, it will only rest on top of the surface area.

This box will be tied into the EXISTING duct work of the house.

AND it will not take any heat from the chimney, so the draft should still be good.

At almost 20 feet of chimney draft, I might need to slow it down anyway.

I also have a fan motor with variable speed, low watts that I can put on the incoming cold air so the motor never gets hot pushing the air thru.

Since the cold air return air is heavier than the heated, I figure that even if the power went out that the natural rising heated air would still push SOME air thru the cycle, and the colder air would drop into the stove.

Effectively aiming the cold air into the stove as I have read, and using the natural rising heat to cycle thru the ducts.

Any thoughts on this?

[ghurd]

I don't think you need the fan.  Gravity is slow but 24/7, where the furnace only runs a few minutes every so often and needs the fan to hurry things up.

Is the furnace still used?  Might want some kind of damper in the new ducts to stop circulation where it isn't wanted when the furnace blower is running.

The furnace may have the same issues with the stove fan.

G

[ridelikethewind]

No, the furnace is not still used, thats the best part.

Just a minor fabrication to tie into all that existing duct.

That is also why the stove is in the basement.

I replaced the single wall low temp flue used for the old furnace, and now have triple walled chimney pipe all the way from the basement to the roof.

And there are no elbows in the whole exhaust path, So I will have to keep an eye on maybe slowing down the draft. dampers

My thought exactly for the furnace, I have a piece of flat sheetmetal as a plenum divider for the existing furnace to direct all airflow to the stove and up.

[GaryGary]

Hi,

Don't know much about this, but I wonder if it would work better if the thing that encloses the drum were built as a cylinder that is concentric with the drum.  

The space between the outer cylinder and the drum could be set so that the airflow velocity over the drum is higher than the arrangement in your sketch -- this should improve heat transfer?

Are you at all concerned that the drum wall might overheat if for some reason the airflow in your new ducting was stopped?  I remember having a not to tightly constructed drum heater in a shop I had years ago, and it was kind of scary when it really got going

Gary

[ridelikethewind]

The bottom of the transfer box is concentric.

You are right about the top part.

Smoother flow, would be better transfer efficiency.

I will look into the material I have lying around.

The drum can handle the heat already with no airflow, the heat transfer box that will be put on top of it will be similiar gauge metal. So it ''should'' be OK.

I will keep that in mind though and definitely monitor it.

One good thing about a unfinished basement stove location is:

there are no combustibles near the stove at all.

Concrete floor that will be top lined with some sand to keep the BTU's coming from the stove from heating the ground needlessly. And unfinished concrete walls, no combustion.

thanks

[scorman]

check out my response to another poster:

http://www.fieldlines.com/comments/2007/11/26/184016/10/16#16

"The stove's firebox INCOMING vent is from the outside cold attic air and is piped down from the attic."

BTW, your intent of using outside air is a bit overrated ..been there, done that

There are two things that need control ...damper on the flue AND reducing air intake.

I have my intakes completely shut off ...amazing how much air is available from cracks at the door,etc ..the actual volume of air from inside the house should be insignificant if you can keep the stack temp around 250 degrees.... we are NOT talking the old open face fireplace hearth!

The amount of heat up the chimney is the temp and the volume ...I use masonry to absorb a lot of the heat content and volume is very slooooow.

I would check out the steel fireboxes that are readily available for "new construction" ... a 30 design can burn a lot of wood ...built in heatalator double wall construction makes the efficiency very high with forced air

I can provide more details if requested

Stew Corman from sunny Endicott

[wdyasq]

I have run both single and dual drum heaters. I will not run a single drum if heat is my major criteria.

IF I wanted to heat as you do, I would probably get a ~'35 gallon' drum and put it inside a '55 gallon'drum. They would be sealed one from the other  I would then duct the air through the smoke free unit.

I lived in a small house in Western Colorado many years ago. The entire heating system was 4 - 6' double insulated glass doors and shutters. It was two story and an approximate 10" round duct ran from the peak of the second floor to below the slab. When the temperature got above a set number, a small fan forced the hot air below the slab and into the two lower bedrooms. There were insulated shutters where one could cover the windows as necessary.  A wood burning stove was on the top floor but it was never necessary to fire it.

By proper use of the shutters, windows and fan, the house could be kept at very reasonable temperatures Summer and Winter. And, we did fire the stove one night after we had had 6 foot or so of snow. The windows and doors had to be opened to keep from overheating the place.

Ron

[ridelikethewind]

Hello Stew, that would definitely work, but I am trying to use materials that I already have.

I'll try that on the next stove.

thanks

[ridelikethewind]

Now the barrel in a barrel sounds interesting.

That would be more effective all around transfer.

I will see what I have around here.

good idea

[scorman]

my concern is that the barrel idea is OK to heat a garage ie not continual useage ..

if you are planning on heating an entire house and burning as I do, about 5 full cords in a season, then the thickness of the metal of a barrel is insufficient to withstand the very high firebox temperatures ...it will get brittle and then fracture ...you'll be able to poke a hole through it with a ballpoint pen

The commercial boxes are burn rated for 20 years ...very heavy gage metal.

Mine has been used for 15 years and no sign of any deterioration.

You might get away if you could line the barrel bottom half with thin firebrick, or else lay a curved piece of sacrificial 1/16" sheet metal there.

Those fireboxes used to cost under $200 ...no idea the current cost ...but compared to a $2000 fuel oil equivalent ..a rather small investment to gain efficiency.

I had tempered glass firedoors installed at one time, but they would break from the heat ...some of the glass fell inside on the coals ...I have a sample of it as a curiosity....the glass melted into a 90 degree curve ...that is HOT!

My grates are constructed from 1 3/8" solid billets ..after three years, they are starting to sag ...I have seen them glowing red.

Do NOT underestimate the amount of heat generated within the box when you damper it down.

Stew

[ridelikethewind]

I agree, it gets considerably hot.

I have witnessed it already.

This only has to get me thru 1 season, and then I will build a much thicker firebox, welding thicker gauge and some type of double lined exchanger inside as the ideas from all here are brought together.

The resources are not there for this season.

The drum will have sand lined at the bottom to deal with the intense heat.

(per the kit instructions, hate to have been the one to discover that the first time!)

A piece of curved sheetmetal as you suggest on top of the sand will also help.

Melting glass? yikes. That 3rd stage charcoal of the wood burn process is the hottest. almost all carbon at that point

thanks

[Volvo farmer]

I also live in Western CO.

High today was about 40F, low in the teens. I ran the water heater to heat the pex tubes in the slab downstairs for about an hour this morning. The solar gain upstairs meant that I came home from work to a 75F house at 5PM. Haven't burned a stick of wood in three days either.

This is our second winter here and I have been truly amazed at what a bunch of south-facing glass and a little thermal mass can do in this climate. It's nothing short of astounding at the amount of heat we collect.

And I do have one thing to add to the conversation. We wanted to put a wood burning stove downstairs. It just made more sense thermodynamically in our house. Upon reading some about wood stoves, I realized that the stove needs to be part of the family. It sounds silly, but wood heat needs pretty constant observation and tweaking. Put a wood stove in your basement, and you will surely be running up and down stairs all winter long to keep the thing running optimally. You have to tweak it, feed it, remove ashes, etc.

We decided to put our stove in our living area upstairs where we can enjoy the heat and monitor it. We suffer a little because the downstairs is a little colder than upstairs. Still, I like having the fire in my main living area. I think we did good in that regard.

 

[TomW]

Farmer;

You are so very correct about placing a stove in a convenient location so it gets proper care and feeding. Sometimes you just want to hang out near it ,too.

Cheers.

TomW

[shiverin]

You might want to check out this website to get some ideas on how other people have done it. http://www.outsidewoodheater.com/.

shiverin

[scorman]

the sand would almost have to have a metal skin over it ...you will have to remove the ash once or twice a week, and you don't want to be digging into the sand each time

somewhere I saw fairly thin firebrick ie 1" thick ...think they use it for lining fireplace inserts....should be fairly inexpensive so check with masonry supply

this would provide a smooth surface not unlike the bare masonry on my fireplace bottom and could negate the need for the metal skin.

you will also need some sort of grate to get air under the logs ..if you use pipe or 3/4 rerod, it will fold like a pretzel in no time as it sits in glowing charcoal

I'll take some pics soon and post a link

Stew Corman from sunny Endicott

[ridelikethewind]

Thanks for all the good info ppl

[ridelikethewind]

Good stuff Stew.

The firebrick would solve 2 issues at the same time.

http://cgi.ebay.com/Insulating-FireBrick-Thermal-Ceramics-K-23-12-pack_W0QQitemZ130177304347QQihZ003
QQcategoryZ3090QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I had thought of welding a thick steel plate with holes in it vertically across the length of the bottom like this:

[thirteen]

I built a house and put the stove downstairs with the chimney coming up through one end of the kitchen and next to the entrance door.  The stove was under the kitchen and it always had a warm floor. Nice in the morning getting coffee started. The only big difference is that the top story was 2.5 ft wider than the bottom floor on each side and 8 ft longer in the front. We made a daylight basement which is great for wood heat and canning of your garden produce. We used an Earth Stove with a thermosat and we only needed to load it twice a day when it was real cold. There was no major duck work but I made several small vents in different locations that provided circulation of the warm air no problem. Kitchen down stairs for summer one upstairs for winter. I made this for myself so there is a lot of things done for myself that are not normally done to houses. My main air return was the stairs, but in each back room there was a floor vent to the basement. The air for the wood stove was piped from outside under the porch. I did not do this to start with but I made the house too air tight and this solved the problem. I never have had another problem with the chimney.  I still have some of the drawings and the reasons for doing heat venting thru the floor, plus interior walls, and in the over hang. Most of the design for the heating was tested at the volunteer fire department which I was part of for 6 years. Using breathable smoke to test air flow was a nice idea.  If you want them e-mail me at (mtrcfritz@hotmail.com).

You might try and find a place to put your fan with a filter in the duct work it will help clean the air for there always seems to be a little dust in the air. You may not need a fan all of the time so a bypass ductwork or a slide out for the fan this would eliminate restriction in the naturel flow of air thru the duck work. You might need to put some more duck work in for the volume of heated air you want to different rooms.

[ridelikethewind]

Sounds good. I'm glad to hear it has worked so efficiently in that manner.

[scorman]

those eBay bricks are the standard thickness ..I was talking about half thickness ie only 1 1/4" thick?

saw a diff eBay ad:

http://cgi.ebay.com/Firebrick-Ashley-King-Wood-Stove-Bread-Oven_W0QQitemZ230163552663QQihZ013QQcateg
oryZ46285QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

but I would look locally ..there is also "castable" material that you just add the sand and water:

http://cgi.ebay.com/INSULATING-CASTABLE-Firebrick-REFRACTORY_W0QQitemZ140184004776QQihZ004QQcategory
Z3090QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

the idea for your grate is a good one ..can't warp ..weld cross support on bottom side

use sand under firebricks to level or cast it in?

I just posted a bunch of pics of my installation (no specific order):

http://s145.photobucket.com/albums/r203/scorman1/fireplace/

feel free to ask specifics on any pic

Stew

[ridelikethewind]

nice pics, how high does that thermometer usually go?

and, I am going to go with  just enough sand to level those 1" firebrick for the bottom, good idea

[scorman]

"how high does that thermometer usually go?"

just checked ...900F ..a real cheapo bimetalic coil design ...should be availabe at any stove store

If you are simply removing heat from the barrel through the sides as in your first diagram, the heat transfer coeeficient is NOT very high for and air-to-air interface, so I conclude that the firebox  may get cherry red. Another reason for utilizing much heavier sidewalls on a firebox to distribute the heat better.

BTW, while you are still working on the barrel design ...any way you could recirculate some domestic/baseboard hot water thru a serpentine set of 3/4" copper tubing near the top of the inside of the burn chamber? As long as there are two drops of water at a solder joint, it can't get unsweated, but you will need an extra storage tank to accumulate the heated water so it doesn't boil. You could probably squeeze seven passes of 2 feet each or about 15 linear feet of tubing ...would cook a lot of water.

Tubes could also be placed on outside of barrel instead, but might get in way of air plenum.

Stew

[ridelikethewind]

Yes, I had thought of the flexible copper tubing on the OUTSIDE and thermosyphoning to a storage tank mounted higher than the stove. And have at least 2 relief valves for pressure.

I will have to monitor how hot the tank gets to get some idea of how close to put the copper coils.

[scorman]

"I had thought of the flexible copper tubing on the OUTSIDE"

I wasn't thinking about flexible tubing ...you could simply wrap around the drum ...nice!

but it did jostle my mind from an old project...

you could purchase at a very reasonable cost ...1/2"OD soft aluminum refrigeration tubing in a 50 ft coil ..trivial to use flare tool or compression fitting to connect to copper system ..should cost 1/2 the price of copper tubing

"thermosyphoning to a storage tank mounted higher than the stove" ..nope, it would boil ..need a small circulator pump

Stew

[scorman]

just found this link for aluminum tubing:

http://www.plumbersurplus.com/Cat/Aluminum-Utility-Tubing/269/List?attribute_value_string|Brand=D.O.
+Smith

Stew

[ridelikethewind]

good link.

although copper conducts heat about 70 percent better than aluminum, at over 100 dollars for 1/2 copper at 50 feet, I think it is well worth it to go with aluminum at 25 bucks the same length! and it will not melt until over 1200 F, so it should be good to go.

[TimV]

Please do this.

 Call your insurance company and tell them your hooking up a "barrel stove" in your basement.

 Then post in here the name of your new insurace carrier.

But I would recommend if your serious about heating with wood and want to keep your old hot air system as back up and house standing as it now is get a well made furnace capable of heating up to 10 rooms or more on as little as 6 full cord of wood in northern NY, look into Energy King 480EK by RJM Mfg. Chippewa Falls Wi.(Just Google )

Just a woodstove in your basement without duct work will make your house feel much better and in most cases is all you will need for heat but for the worst days of winters cold.

If your feet are warm your warm!

And on your pipe for air from the attic...Your only burning firwood not using forced air to atomize fuel oil in a gun burner so i dont think you be sucking the curtins off the windows with a woodstove. Lots of luck we all need help with heating bills this winter.

by the way the House today is solving all our energy problems and our current president said today he will veto any bill the get to him. seems the oil companies dont want hear of new conservation measures but thats political for another forum.

Excuse my typing I dont own a spell checker