Indoor furnace outside and everything between

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Michigander

New Member
Sep 21, 2016
3
Michigan/Indiana Line
So I just want to start off by saying this is my first post and I am 100% new to alternative heat sources. I have lots of questions and I'm sure most of them have been answered in some form or another in other threads I just wanted to hear some advice specific to my exact situation so please bear with me.

So I have a 960sqf house built on a slab. It's standard gable roof 8ft ceilings 3 bedroom house so every inch of floor space counts. It was renovated in 2013 torn down to studs including new blown in insulation. Currently I have forced air electric heat. My first electric bill when I bought the house in December of 2014 was over $350. So I'm looking to get away from that.

My current electric furnace is in my attic with what looks like insulated flex ducts. I am on a very tight budget and was hoping to buy a used unit and install myself.

MY PLAN: buy a used indoor furnace and place it outside in either homemade shelter or a sheet metal shed and run my heat through either my soffit or through the wall of my attic into the cold air return of my existing system. My house is small and well insulated so I guess I'm not terribly afraid of loosing the btu's of having it outdoor. But from what I have read is that it's not good to use a wood furnace with the flex tube. An tips or advice to the things I've mentioned and definitely the ones I have not is very much appreciated!!
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,265
South Puget Sound, WA
Welcome. I would not be jerry-rigging a furnace like that, wood or otherwise. Have you considered a wood pellet stove or a freestanding woodstove?
 

Michigander

New Member
Sep 21, 2016
3
Michigan/Indiana Line
I have considered a wood stove but I have a small house and floor space just isn't really an option. I want an outdoor wood burner that way I am not compromising usable space and I do not have an open floor plan. I have 10 acres of woods so I have a free supply of wood. I looked into pellet stoves but again why pay for fuel when I have a free supply of wood. Right now I am trying to get something safe that will work temporarily and over the years I will upgrade to something permanent. My budget is $1,000. I can pick up a used unit for only a couple hundred dollars and the rest I figured would go into piping and the shelter for the unit.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,374
NE Ohio
Any wood furnace on CL for $2-300 will be a huge disappointment and source of frustration. I'd build a little bump out/alcove on the side of the house to put a stove in.
Those outdoor furnaces were popular for a very short time around here...then a bunch of used ones for sale...now you hardly see 'em...new or used.
 

mike van

Feeling the Heat
Apr 24, 2013
362
Kent Ct
Don't throw your money away on some used p.o.s. that should probably go in the scrap metal pile. Then compound the problem by installing it too close to your home [hot air doesn't cover distance well] Many of the people here have spent 15k on their wood fired system, you just aren't going to get something that works for a thousand. Money wasted.
 

DoubleB

Minister of Fire
Mar 4, 2014
658
NE Wisconsin
I agree that's asking for trouble. For example, no good way to dissipate heat in a power outage, because the air registers are going to be lower than the ductwork, probably also lower than, or not any higher than, the furnace itself.

I believe you that space is tight, but it seems to me that a freestanding woodstove is probably your best option and the price you would have to pay for wood heat. Unless you want an outdoor wood boiler (hot water), but that's many many years of $350/mo electric bill until you have payback.

Look at the bottom of this post for a couple pictures that reminded me of your question: https://www.hearth.com/talk/threads/everything-drolet-tundra-heatmax.140788/page-55. Also read a few pages before and after for feedback on it. That poster was pleased with his set-up, but most here agree it's a time-bomb waiting for trouble that won't be worth $350/mo during the winter.
 

maple1

Minister of Fire
Sep 15, 2011
10,556
Nova Scotia
On the flexible ducting - no, not recommended.

I'm not so sure it isn't very good to have it with your existing electric furnace, either.
 

hondaracer2oo4

Feeling the Heat
Jan 18, 2012
414
Canterbury NH
Your budget is a little too light for accomplishing what you want to do. When I was younger and had just bought a house, I purchased a outdoor boiler used that needed some welding because of the previous owner trying to do something he should not have been trying to do, not because the boiler was rotting. I picked up a hardy h4 for $500 and that was dirt cheap. After that I had to pour a pad for it $100. Then I had to run power to it $100. Then I had to run lines to the house $100 for pex, $500 for spray foam in the trench. Then I had to put a water to air hx in the furnace plenum $200. Then I had to connect all the pex lines with fittings and shut offs etc$100. Then everything else that Nickle and dimes you on a project probably was $3-400. So I was in the range of $2000 and that was as cheap as I could do it. I ran it like that for 5 winters. I went through 12-13 cords per season heating a 220 year old home in New England. I finally bought a gasser last year. Burned 7.5-8 cords last winter. Good luck with your project.
 
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blades

Minister of Fire
Nov 23, 2008
3,523
WI, Leroy
basic premise is ok idea of execution wrong. there are outdoor hot air furnaces. indoor unit in metal shed do able but you would need to insulate it, creating a shed with in a shed. Insulated ducting would need to rigid type . the feed in point on existing duct work would be the plenum of the current furnace , return would need to be tapped to cycle back to outdoor unit. The system will require a dampers to isolate the electric unit. could be manual or auto. Solid fuel heating appliances are supposed to have a 2" clearance on the first ten ft of ducting out of the plenium and 1" there after to combustibles. By the time you would get this all sorted out and the expense- knocking a portion of a wall out and building a alcove for a free standing stove might be cheaper and faster. There also the option of a very close clearance fireplace/ insert arrangement that might work also such as used in mobile homes. I do not think that any of this is going to be do able on $1k unless you are willing ti give up some space inside for a free standing stove + sweat equity. In which case you just might make it. In my area across the pond from you ( lake Mich.) there have been used insulated flue assemblies on CL . ( a 15ft flue assembly can run a grand all by itself) Haven't been any epa style stoves of late on CL but right now is the sale time on stoves at dealers. Englander and Drolet are 2 brands which I would recommend might be some others, these I have personal experience with. a 2-2.5 cuft stove would likely work well. These are epa approved basic steel stoves ain't fancy but get the job done - best bang for the buck. In the long run it might be better if you would just seal the place up tight and insulate the H... out it for the $ invested in that it would provide a better return right now and down the road.
 
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peakbagger

Minister of Fire
Jul 11, 2008
5,509
Northern NH
GIven your location, you are far better off buying a mini split heat pump. It will cut your power bill by about 2/3rds and will cost far less than what your propose to do. This gives you summertime AC and heat in winter down to about 30 F. The heat pump runs down to about -10 but you will need supplemental heat which you already have.
 
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Bootstrap

Burning Hunk
Dec 4, 2013
150
Northern CT
I have a Englander 28-3500. I saw a review picture on homedepot.com that showed what someone did. He installed it outside. It would suck inside
air, and the top ducting was piped back into the house.
28-3500.jpg
 

begreen

Mooderator
Staff member
Nov 18, 2005
84,265
South Puget Sound, WA
The 28-3500 is an add-on furnace, so this installation is off-label. My main concern is clearances. The supply plenum appears to be in direct contact with the wood siding. Given the potential temp of the plenum I would expect there to be clearance from combustible of 1 or 2" there. But as noted this is off-label and therefore an untested and uncertified installation.
 

stee6043

Minister of Fire
Aug 22, 2008
2,648
West Michigan

stee6043

Minister of Fire
Aug 22, 2008
2,648
West Michigan

Bootstrap

Burning Hunk
Dec 4, 2013
150
Northern CT
It may be an "uncertified" installation but its the most accurate answer to the posters question. Maybe the installation I posted could stand to be improved. However, I would prefer a add on furnace like that over a forest eating boiler. Those things eat wood. Plus, not all areas allow those boilers. He may be in a residential area.

So anyways, you could certainly install an add on furnace and pipe it back into your house. If you look at the picture I posted, you will see that there is a concern about clearance to combustibles. The pipe that comes off the top of the furnace, where the heat comes out: I would want that to enter the house through some kind of metal through wall thimble. After it enters, I would probably terminate it right there, so its not near combustibles. I think Lowes sells an 8" through wall kit. If the power ever went out that pipe would get really hot.
 

stee6043

Minister of Fire
Aug 22, 2008
2,648
West Michigan
It may be an "uncertified" installation but its the most accurate answer to the posters question. Maybe the installation I posted could stand to be improved. However, I would prefer a add on furnace like that over a forest eating boiler. Those things eat wood. Plus, not all areas allow those boilers. He may be in a residential area.
You're proposing that an add-on furnace would generally consume less wood than a boiler, all else being equal?
 

Bootstrap

Burning Hunk
Dec 4, 2013
150
Northern CT
Lets put it this way. In a 960 sq-ft house, yes the outdoor boiler would consume more wood. If he were heating a 3000 sq-ft drafty old house then maybe not. That's my opinion anyways.
So all else being equal depends on what that all else is.
 

Highbeam

Minister of Fire
Dec 28, 2006
17,659
Mt. Rainier Foothills, WA
I live in a 1650-1700 SF house. We have enough room for two stoves. You have plenty of space to install a regular woodstove. Modern units can be very close to the wall so minimal loss of floor space or you can build an alcove bump out but I would just put it in a corner somewhere.

You will love the intense free heat from a woodstove.

For your budget about the only other way to heat with wood is a pellet stove that is inside, again close to a wall, but the chimney vent can just shoot out the wall and terminate until or unless you want to run the small vent to the roof.

You can't do much with 1000$. We are also all electric (wall heaters) and I've only ever run the electric heat to test it. Wood heat is great.
 

stee6043

Minister of Fire
Aug 22, 2008
2,648
West Michigan
Lets put it this way. In a 960 sq-ft house, yes the outdoor boiler would consume more wood. If he were heating a 3000 sq-ft drafty old house then maybe not. That's my opinion anyways.
So all else being equal depends on what that all else is.
Roger that. Just as a suggestion you may want to do a little more reading around here and on other sites regarding types of wood burning appliances and their relative efficiencies. Heating water with wood is generally accepted as always being more efficient than heating air with wood when the ultimate goal is to move that heat from one place to another. The size of the house is largely irrelevant.
 

Bootstrap

Burning Hunk
Dec 4, 2013
150
Northern CT
I'm not saying the boiler isn't more efficient. What I am saying is that a boiler(or at least the ones I am familiar with) are much larger than a furnace that he would need and because of that, would need more fuel to burn properly. For his heating space he could go with a small furnace or even a wood stove.

To me, if I were to go with a boiler I would want to not only heat the house, but a shop or garage as well. To put in a wood boiler to heat 960 sq-ft seems excessive to me.
 

leaddog

Minister of Fire
Sep 24, 2007
933
Hesperia, Michigan
I think a pellet stove will do what you want at lower cost that what you now have. Here in Michigan pellets can be had fairly cheap if you buy by the ton. They are easy to maintain and can be vented straight out the wall. They take up very little space. Just because you have wood doesn't make it cheap. Chainsaws, splitters, tractors, trailers, malls, storage sheds, TIME all add up. Right now I have a boiler and lots of wood but I just had my propane tank filled for a $1 a gal. and that makes it almost more costly to burn wood. I also have a pellet insert that I use because I like the visual and that alone will heat my house. The only reason I'm using the boiler is I heat my hot tub and DHW along with the house. When my boiler fails I think I'll just go with my propane on demand boiler and pellet stove as my house is now all radiant. If it wasn't radiant I'd just go total pellet.
leaddog
 
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