unconventional stovepipe run to save more heat?

You're looking for heat transfer. Attaching some metal fins on the straight chimney would probably do as much for the heat transfer and eliminate the obvious problems with running a chimney section upside down. I'm sure there are factory built units, or you could rig one for yourself fairly easily.

If you've got a good stove and you keeping a good hot fire you shouldn't have to worry about creosote, and a long run of flue pipe or a Magic Heat is a great way to get better efficiency from your stove. Get an old Magic heat, the one with about ten tubes in it, there's a new one that has four tubes, you'd be better off with a long run of flue pipe..

Looking at the site you referred to.. I've found Mother Earth News to be something that's probably great for hippies, but the "Far Out!" factor dwindles rapidly as the temperature goes below zero.. This is classic: " According to its builders, the fireplace will ? when loaded with five pounds of wood and lighted ? give an instant dose of heat to the room through its stovepipe." No matter the efficiency, what good is five pounds of wood heat?

If you make a run of pipe down toward the floor and then back up you'll probably get a much better heat exchange.. it might be a little harder to get a good draft if the house is cold but a couple of sheets of newspaper wadded and blazed as you're starting the fire should take care of that. If you get the pipe closer to the floor (and into the colder air) it'll naturally heat the air more efficiently. The more the pipe changes direction the more heat transfer you'll get for a given length too..

John

Some wood stoves introduce air into the flue leaving the stove to burn off creosote in a box just before the chimney. Note that creosote is a volotile that condenses out of the flue gas. If you are condensing water you will condense creosote also. Nick is correct about the efficiency increase, however there are problems with a wood burning appliance. Condensate in the flue is slightly acidic, the flue pipe should be designed to handle it. If you condense the water out of the flue, it will be too cool to establish a good draft. You will need a draft inducer. DO NOT USE a muffin fan. Tjernlund makes them for gas burners, see if they make one that would work with wood.

Your idea is interesting, but fraught with peril, as the side effects of what you propose could be dangerous. Buying a good quality air tight wood stove will increase your efficiency safely without having to jury rig a lot of questionable doodads that may not work as desired. Good luck.

Stretch

Draft might come from a 240 V muffin fan running on 120 V over an adjustable hole in the door. Dry creosote buildup may be unlikely in a chimney with condensation, which can add 15% to efficiency.

To cool a 6" pipe inside an 8" pipe, you might use a 10" fan in a 10" to 8" reducer below an 8" T near the point where the 6" pipe leaves the house to blow room air back towards the stove through the space between the pipes, with a CO monitor in the room.

Nick

Couple of issues:

1. To have natural draft, you need temp diff for some vertical run.
2. When firebox temp below about 1000 deg F, unburnt volatiles escape, to condense in cool areas (from top, down).
3. Air drawn into device affects overall efficiency big-time, since it's heated. (So the 90% claim sets off my BS-alarm.) Not to mention biggies about Fire Marshall, insurance, etc.

To go for extreme efficiency, as others have discovered, you first need complete combustion: temp, air-fuel ratio, mixing. Insulated firebox with controlled draft help a lot. Then you can transfer heat as possible. For really extreme efficiency UMO Prof. Hill used forced draft.

Using available items, avoiding electrical requirements, I'd suggest:

1. EPA-approved non-catalyst woodstove of output and quality to suit you.
2. 6-8 feet of single-wall black smokepipe, with all sections angled up or straight up.
3. Fuel that is as dry as you can make it, fed in such a manner that it does not quench flames if possible.
4. Sacrificing efficiency on occasion by allowing extra airflow, on startup to heat flue, and on loading fuel.

Taking it a small step further, I use a few small pancake blowers to stimulate airflow over hottest part of stove, and past lowest part of pipe.

Installation should be done so as to meet all codes, obviously.

Not a conversation-piece like the one in the article, but it can be made to work very well. YMWV.

HTH, J

I'd suggest using standard double walled pipe with the shortest / most direct vertical route possible. I'm interested in finding out how they came up with 92.6% efficiency - doubtfully using any accepted UL methods.

Problems with the convoluted stove pipe will be:

1. Your building/fire inspector won't pass it
2. Your insurance wouldn't likely give you coverage for your house
3. Major creosote build up due to bad flow
4. PITA for cleaning

I'd spend my money on a good, efficient, modern stove. I've found deep ones better at burning than wide ones. Go double walled. If you want more heat then use a fan to blow air around the stove.

I agree that a modern, airtight, etc. woodstove would be a nice alternative, but I don't have a couple of grand sitting around to buy one :) I'm not quite sure who some of these stove companies think their market is, but in my neck of the woods I don't know too many folks with that kind of money available. I'd like to see a few more decent quality stove options for average folks and their paychecks...

In any case, I like fin idea. This would seem to avoid all of the potential problems several folks have raised with a convoluted stovepipe run, but still allow you to get some decent heat transfer...

I am installing a wood stove myself. Initially I thought I could just remove my natural gas stove and replace it with a wood stove. This vents into an existing brick chimney.

I learned that my homeowners insurance would not cover me for a fire if my wood stove was not installed to code, inspected and passed, and also inspected by my insurance company.

So I could lose *everything* if I just stuck a wood stove in my house!

I am going the permit route which requires all sorts of stuff, but for your specific situation, read the following which is from the Selkirk chimney manufacturer's frequently asked questions link below.

"Are there any limitations to the use of elbows?

Yes. The UL 103 Standard, our instructions, and codes prohibit any offset creating an incline greater than 30° from vertical. The use of a single

Sorry I would have replied quicker but I was too busy laughing once I saw the webpage.

While something like this might be a conversation piece in Arizona, on those cooler nights.

I wouldn't suggest relying on it in Minnesota, or anywhere else north of Tennessee.

And it does CLEARLY say this is a fireplace not a woodstove, so the chimney is designed for that

First issue is creosote buildup. How are you going to know WHEN it's time to clean it ? Without pulling it apart every week. That could get very messy, and there is that "fire hazard" thing, if a chimney fire starts how are you going to put it out ?

Fireplaces and woodstoves are two different things.

In a sealed woodstove the idea is to cut the rate of combustion by holding back air that would otherwise go up the chimney. Raising the actual temperature in the firebox to allow complete combustion of the fuel.

This usually means a woodstove chimney is much cooler than a fireplace so condensation and creosote, and draft is more of an issue.

But since this is only an opinion that you can ignore.

my vote is "don't do it".

AMUN

I need to go see my building inspector to ask some questions...

I printed out a copy of the above stove. I think I'll show him the picture and tell him I have my stove in. Then ask if he thinks my installation is ok. Maybe do the same for my insurance guy! (They will get a kick out of this.)

FYI - I have had to get an EPA certified wood stove, install a hearth pad which has an R-value minimum of 1.5, have 14 inches space from stove to wall (depends on stove model), have 18 inches of hearth pad in front of stove, 8 inches of hearth pad on sides of stove, and a U.L. cert. stainless steel chimney system installed to code.

Fins would work better, but what do you use for the fins? I've never seen them sold and it may be a hassle to cut them from sheet aluminum.

Or periodically replaced... 3 5' lengths of galvanized pipe should do.

Nah. Use a $5 muffin fan. This goes on the OUTSIDE of the door.

La di dah. Life is dangerous. Use a CO detector or two.

Nick

When the first chimney fire strikes, you'll have a lovely time. This sort of foolishness is a bad way to "save money" when all the costs are included. Put the woodstove in with a nice normal stovepipe and make sure it passes inspection (which this sort of crap won't).

Inspections of this sort are about "not burning down your rather expensive house" and "not gassing your family to death", rather than "trying to prevent you from squeezing 25 cents worth of heat out of your woodpile", but believe what you like. If you read MEN without a large block of salt handy (a grain just won't do it) you may teach yourself some expensive lessons you're not ready to learn any other way...

That has got to be one of the stupidist ideas I've seen TMEN show, and they've shown a lot of stupid ideas.

The convolutions are ridiculous. Back when huge grange halls were heated with little more than a tiny pot-belly stove, the stove sometimes had a straight pipe leading to a T, which then led to two 90 degree elbows, which led to two vertical pipes, which led to two more elbows and another T, merging into a single pipe going through the roof or wall. Note that these scavangers were designed for use with coal, which provides more heat and less creosote. In any event, that double stack is a tried and workable design. Convolutions that attempt to make hot smoke go down may be fine for hippie hookahs, but they don't work in home heating, especially if you are trying to start the stove on a mild day where there isn't a strong darft.

The design that TMEN shows is guaranteed to be a PITA. Additionally, even if it worked properly, you would get a quick blast furnace type of heat every time you fired up the stove. That gets old fast, usually after about the third firing of the stove.

The other part of the article (the stove itself) is equally stupid. It doesn't address that refractory cement can crack, especially if struck. Without at least an embedded chicken wire or hardwood mesh, I wouldn't trust such a stove to not fall apart at precisely the wrong time.

The small amount of fuel the stove can accept means that it requires constant feeding, probably on the order of once an hour or even once every twenty minutes on a cold windy night in an older house. There are only so many BTUs in a pound of wood, no matter how you cut (or burn) it.

The design doesn't even qualify as a nice idea poorly executed. The fireplace/stoves that they attempted to emulate had one major plus, lots of thermal mass. They removed the thermal mass and kept the bad parts of the design.

Hey I hear you on the price issue. Either hurt now or hurt all the time later. If you have a cheap stove your heat goes up the chimney and you are spending your time/money loading the stove with wood.

Keep an eye out at liquidation places etc. I've seen brand new $2K stoves selling for $800.

Uhh, make that hardware cloth and not hardwood. :-)

Have you checked out used stoves on ebay and craigslist? Used stoves are more $$ this time of year than any other, but still a lot less than new. Some of them are barely used and in excellent condition.

I personally view a high end wood stove as a long term investment. Spend $2500+- on a stove, pipe, hearth, chainsaw, and maul today to you can reduce your heating bill by $1000+- per year for the next 20 years. Also you can sell a high end stove as "decorating the living room" to a wife. :-)

A much safer idea than the crazy pipes you were considering.

If appearance isn't a big issue:

I disagree. You can make the flue gas go down and back up, as I posted before you just have to give it some quick heat to establish a good draft while you light the fire. Old furnaces with a heat exchanger that took the flue gas from the top of the furnace and sent it to the chimney down low were common, I've got one in the basement and it works very well. Three feet from the back of the appliance the pipe is about 200F, pretty good efficiency..

The method of extracting more heat from the pipe that you mention was a common one in the old days, but it requires more vertical room between the top of the stove and the ceiling than many houses have today to work well.

I fully agree with your opinion of the MEN stove, a massive waste of time and resources.

John