Wood Boiler - Outdoor wood furnaces

6e · #21 12/08/10, 09:01 AM

Quote:

Originally Posted by Beeman

I'd like to know more about the actual mechanics of them.

Obviously you have a box outside which burns wood and transfers heat to the house. How does it transfer the heat? What type of piping and fluid does it use? What type of heat is used inside the house and how does the heat transfer? What circulates the fluid? Does it physically heat your domestic hot water or does it transfer that also? How does the weather effect them? I've seen some with a building built around them to protect them and the wood.

I think many that consider them don't realize there's more then just the box outside that burns wood.

What it is is a little mini building that is VERY well insulated that is brought in on a truck and set up. In the middle is a fire area. Around that is a water jacket. The fire inside the box heats up the water which is then pumped through underground pex lines to your central heater to a plenum that's in the furnace, much like your central air unit is set up. The blower kicks on and blows over the plenum with hot water in it heating up the air and the water circulates back to the wood furnace outside and is reheated. When the air inside the house is warm enough, a thermostat on the furnace outside shuts the damper and brings the fire down to a smolder. When it goes to heat, the damper opens up and gets the fire going again and the whole process starts over. I haven't seen weather affect the furnace itself and it's not unusual to see snow sitting on the roofs of those little furnaces. They are very well insulated.

**Kris in MI** · #22 12/08/10, 09:32 AM

Several posters above mentioned smoke problems. What we've noticed with ours is that quality of wood makes a huge difference in how much smoke-- and what kind--you get. (The yucky stinky kind or the good kind that makes you say "mmmm bacon!")

When we burn 'junk wood' we get lots of the thick stinky smoke that hangs around. When we burn good stuff like oak and black cherry it's a nice white thin smoke that smells delicious. That's the stuff where the person who stoked the fire comes back into the house and everyone inside gravitates toward them saying "mmmm bacon!"

Tom VH · #23 12/08/10, 10:04 AM

We've had a 6048 Central boiler (comes with a 20yr warranty) for five years to heat 2500sq ft and hot water. We are slab on grade so we put in three in floor zones, for the floor we use a plate exchanger for hot water we have an electric water heater with a side arm exchanger, Ive never hooked up the electric, in the summer we lode wood about twice a week, in the winter -20 we load once a day, twice in heavy wind (we're a bit leaky). I think we use about 7 cords per year, we have lots of woods around for our needs, but I know some one who orders a semi load of logs to cut, I think that's pretty reasonable. They have three outlets for three biulding, we buried our water line at 4ft. We would do it again for sure.

6e · #24 12/08/10, 10:18 AM

Quote:

Originally Posted by Tom VH

We've had a 6048 Central boiler (comes with a 20yr warranty) for five years to heat 2500sq ft and hot water. We are slab on grade so we put in three in floor zones, for the floor we use a plate exchanger for hot water we have an electric water heater with a side arm exchanger, Ive never hooked up the electric, in the summer we lode wood about twice a week, in the winter -20 we load once a day, twice in heavy wind (we're a bit leaky). I think we use about 7 cords per year, we have lots of woods around for our needs, but I know some one who orders a semi load of logs to cut, I think that's pretty reasonable. They have three outlets for three biulding, we buried our water line at 4ft. We would do it again for sure.

Who makes that 6048 that you have?

6e · #25 12/08/10, 10:20 AM

Quote:

Originally Posted by Kris in MI

Several posters above mentioned smoke problems. What we've noticed with ours is that quality of wood makes a huge difference in how much smoke-- and what kind--you get. (The yucky stinky kind or the good kind that makes you say "mmmm bacon!")

When we burn 'junk wood' we get lots of the thick stinky smoke that hangs around. When we burn good stuff like oak and black cherry it's a nice white thin smoke that smells delicious. That's the stuff where the person who stoked the fire comes back into the house and everyone inside gravitates toward them saying "mmmm bacon!"

I'll tell you, around here it's slim pickins on what kind of trees you get. Most of the wood available here is Elm, Cottonwood, and Hedge, but we also do get some Oak, Black Walnut and a couple other hardwoods. I personally think all wood fires smell really good. I love that smell. :-)

agmantoo · #26 12/08/10, 11:06 AM

Beeman

I have installed approximately 8 of the "water stoves" and actually owned 1. I have serviced probably a dozen. There were 4 different brands involved.

There are several versions of these heat sources. One, tank and firebox built together, stores the heat in the water (extremely large tank, approximately 1000 gallons) and the fire is permitted to die down. Another has a much smaller tank and uses huge amounts of wood that smolders between the times it needs to burn to reheat the water. Both of these designs smoke a lot because they seldom are called upon to burn hot. There is a 3rd type that I have never seen but seems to have merit other than its high initial price. The first two I referenced weren't cheap, starting at $5000 up plus installation. You can install the unit yourself. Back to the third type. The fire box is not much more than a quality wood stove with a heat exchanger. This unit has the heated water for the heat reserve in a separate tank than the firebox. Using a large tank to store hot water reduces the frequency of having to fire the firebox. However, when the firebox heat needs elevated the fire needs to be hot for a longer time resulting in a much hotter and much much cleaner burn. Once the stored water temperature is elevated the fire can be permitted to reduce to nothing but coals. Again this drops the smoke to near zero. Some of the advantages are

1) The unit is in two parts. The storage tank should last nearly forever. The extremes of heat from the fire and cold from the water are not present in this design. I have seen 4 of the 8 other designs that I serviced with tank or firebox cracks.

2) The separate firebox would IMO permit the stove to heat more uniformly avoiding a lot of metal stress that permits some designs to crack and the doors to warp. Should a problem surface a repairman can access the fault unlike in most designs. Worst case only the firebox would have to be replaced.

3) The unit is more efficient because it burns hot and is then permitted die to coals or to go out. There would be almost no creosote. Creosote is a major problem with all the units I have serviced or installed, regardless of brand.

My experience with the first two designs is that after 10 plus years they are off to the scrap metal recycle yard. If interested, the third type unit can be seen here
http://www.woodboilers.com/heat-storage-systems.aspx

PS..I personally prefer a Geothermal heatpump. Both the waterstove and the heatpump are in the same price range and you get cooling off the heatpump. In total I think that the cost of operation and ownership is cheaper with the Geothermal

Tom VH · #27 12/08/10, 11:42 AM

6e, Central Boiler is the brand name. We have ours located east northeast of the house so the wind is usually in our favor, as was said they smoke heavily only when they're just starting up with a new load of wood, or with crappy wood. once it gets going on hard wood, there's almost no smoke at all.

matt_man · #28 12/08/10, 08:17 PM

Quote:

Originally Posted by 6e

OK, we've been kicking this idea around for awhile and now with it costing over $400 for 200 gallons of propane........it's finally time to bite it and just buy one. Sooo.....for those of you that have wood boilers.........

What brand would you recommend and why?

What brand would you definitely stay away from?

What all do you heat with your boiler?

How long have you owned the brand you have?

We thought about hooking ours to our house of course, but thought about adding a green house and hot water tank.

We have a Central Boiler. We have had it for 7 years and love it. We heat our 2500 square foot house and a 16x32' greenhouse with it. We hope to get it set up to do our hot water also next year. The model we have we can hook up to 3 pumps to it. We have separate pumps going to the house and greenhouse.

I like the fact that there is a separate thermostat that controls the boiler and one that controls the blower in the house. We get even heating that way without extreme hot and cold fluctuations in the air temp inside.

ladytoysdream · #29 12/08/10, 08:56 PM

We have a Central Boiler 5036. This is our 3rd winter with this outside wood boiler. Our's maybe a bit close to the house at 26 ft but because of our set up, it was the best we could do. The water in these units are a closed set up. The hot water goes to our hot water heater first through the heat exchanger and then to our propane furnace with the heat exchanger under it, ( the propane is shut off), but we use the blower to move the hot air through the furnace ductwork under the house. We heat 1250 sq ft of house on one level. We keep the temp 75 plus. Last room in house has no registers but a open door and a window let warm air move through. That room does not get below 60 even on a cold day. Our house is 24ft wide by 52 ft long.
We have a second set up for a another run, on the furnace with the thought of someday laying a second line of pex to the garage. Another thought was maybe a small green house. We burn about 14 FACE cord a winter. So that would be 5 regular cord max.

We use propane for our cookstove only now. That is averaging about $ 7 a month for that. When we heated with propane, it was 500 gallons for the year.

Our closest neighbor is 1/4 mile one way, and 1/2 mile the other direction.

We only burn wood in our unit. Seasoned wood is the best, and green wood needs to sit for next year

I wish we had done this sooner. A lot cheaper for us to heat this way and a lot warmer house. The wood now is our ONLY heat source. We do have a small generator if we lose power.

He started our unit up on Sept 11 this year. We normally run till sometime in May.

6e · #30 12/08/10, 10:48 PM

Quote:

Originally Posted by ladytoysdream

We have a Central Boiler 5036. This is our 3rd winter with this outside wood boiler. Our's maybe a bit close to the house at 26 ft but because of our set up, it was the best we could do. The water in these units are a closed set up. The hot water goes to our hot water heater first through the heat exchanger and then to our propane furnace with the heat exchanger under it, ( the propane is shut off), but we use the blower to move the hot air through the furnace ductwork under the house. We heat 1250 sq ft of house on one level. We keep the temp 75 plus. Last room in house has no registers but a open door and a window let warm air move through. That room does not get below 60 even on a cold day. Our house is 24ft wide by 52 ft long.
We have a second set up for a another run, on the furnace with the thought of someday laying a second line of pex to the garage. Another thought was maybe a small green house. We burn about 14 FACE cord a winter. So that would be 5 regular cord max.

We use propane for our cookstove only now. That is averaging about $ 7 a month for that. When we heated with propane, it was 500 gallons for the year.

Our closest neighbor is 1/4 mile one way, and 1/2 mile the other direction.

We only burn wood in our unit. Seasoned wood is the best, and green wood needs to sit for next year

I wish we had done this sooner. A lot cheaper for us to heat this way and a lot warmer house. The wood now is our ONLY heat source. We do have a small generator if we lose power.

He started our unit up on Sept 11 this year. We normally run till sometime in May.

Your house sounds like our setup. About the same size and all. My main concern is that our house is on a concrete slab and all duct work is in the ceiling. So, that creates a bit of a problem about how to get the water lines to the furnace since going under the slab isn't an option. I was thinking about running the lines up the side of the house, through the attic and down to the furnace, but it would have to be SUPER well insulated to keep from losing too much heat. Thoughts?

**Ross** · #31 12/09/10, 05:37 AM

We ran the lines up the side of our 3rd building and simply boxed them in with extra insulation. The unerground line we used is called ecoflex, there are diferent types andit really wouldn't matter which brand you used. Having the pump on the stove helps keep it primed but getting th eair out of the line is difficult. You'll want a hose hook up to back feed both lines with water and valves to shut off the full lines until you're ready to start the pump. Then as the water is pumped up the falling water helps pull up the water too.

ladytoysdream · #32 12/09/10, 05:52 AM

Our house is a double wide with 6 inch walls. Has always been well insulated. We sit on a pier system of 40 concrete pillars. Think concrete ice cream cone shapes that are 4 ft in the ground. From the ground flat surface, we are using concrete blocks to sit on. Our ductwork runs under the house. We are all closed in underneath with wood boards. Our house was bought new 20 yrs ago. We used propane to heat with for 18 yrs and only 500 gallons a year.

Four and a half years ago, we decided to do a upgrade. Our place was paid off. We borrowed money to add a room 12 by 24 ft, a 10 by 52 ft deck/porch so the roof was extended that side the 10 ft out. So current structure is 52 ft long, and 34 ft wide. My son and his business partner did the work for us. We bought all the materials. So we now have T-11, the thicker stuff for siding, all new windows entire structure, and new shingles entire roof. Our original house was 24 by 40 ft. Then two and one half years ago, we bought the wood boiler. Our utilities are decent to pay.

agmantoo · #33 12/09/10, 12:13 PM

6e

On one of the units I installed I needed to go into the ceiling and I did as you suggested. The house had vinyl siding and I went all the way to the eve and accessed into the house there. I had a sheet metal shop bend a piece of matching aluminum to go over the piping. It is hardly noticeable.

ronbre · #34 12/09/10, 01:45 PM

we have a zero emmision outdoor wood boiler and we like it really well as there is no smell or smoke outside..however, the co we bought it from went out of business when we bought it which voided our warranty and then when we needed repairs we had to make do on them ourselves..so that was a real bummer.

make sure you have a good LOCAL company that will support your furnace and definately go with zero emmisions..don't buy one that is rated too large for your home you are heating or you'll waste wood..we got too large of one..even though we are heating 3 buildings with it we do waste wood.

otherwise we like it really well

we have neighbors that use a non zero emmissions furnace and they smell up the neighborhood for 3 blocks each direction

Beeman · #35 12/09/10, 04:59 PM

Ok, so the fluid that's heated to transfer the heat is water. What if you don't use it during a deep freeze? I'm sure the lines would be buried deep enough but what about the water in the jacket of the stove? Is this water piped directly to the hot water or is there a heat exchange for the domestic hot water? Is there an electric pump like circulated hot water heat that activates by the thermostat? If so will it circulate heat without electricity? Has anyone tied it into a circulated hot water heat system or is it all forced hot air with a fan?

I've seem many of these and yes some look like a little shed, but I have also seen many where they built a shed around it also. That seems to give you a taller chimeny to possibly keep the smoke higher.

**Ross** · #36 12/09/10, 05:26 PM

I have mine hooked to fan blowers but there's no reason you couldn't use radient floor or baseboards. I'm not sure why you wouldn't be using your boiler durning the deep freeze, but if it stop circulating you would have frozen lines. The system needs electricity it is a reality you have to deal with. I should get a solar system to run things full time but I plan to use a generator fo now in emergencies. 2 amps for the boiler, 1 amp for each pump. Mine needs 5 amps to survive. 600 watts.

ChristieAcres · #37 12/09/10, 05:27 PM

It may help some to consider using radiators, as needed, hooked up using a closed system to the hot water heater, set to thermostats, like ours is. That requires a water pump on that closed loop system. That could be used in a combination approach to heating when there is that far off area of the house... Otherwise, you can have both a circulated hot water system, as that works for your house, and also a forced air option. We are set up to do it all using a wood stove. Now, that requires a fan, and another water pump, as the wood stove heats the water and sends it to our water heater (multiple pressure relief valves). Now, when Len builds our boiler, we will be carefully planning what it will be used for in the Winter, since we enjoy our well setup wood stove and not taking that out. We have a garden cabin & little greenhouse that could use heat... This has been a great thread for ideas!!!

agmantoo · #38 12/09/10, 05:59 PM

Beeman

Water is the primary liquid that is circulated. Yes there can be a problem with the lines that are near the surface if the heater is not fired for some time. Most folks that are gone for a short duration just circulate the water through the house exchanger and leave the unmanned house heat on. I have heard of using an antifreeze (environmentally friendly type) but have never seen it in use. The makeup water to the water heater is fed through a separate line and is not shared with the heat water. Heat water may not be potable whereas the water heater water remains potable. In the better systems the house thermostat activates the circulating pump for the heated water then after a predetermined time the air circulation blower is switched on. Delaying the blower prevents an inrush of cooler air at each on cycle. No electrical power and you have no heat. The water stove will function with both forced hot air and circulated hot water. The wiring is different obviously. I have been around both styles of housings for the heaters. For myself, I like the unit inside an enclosed building. It is nice to be out of the weather when attending to the stove. Additionally, having some good dry wood stored adjacently is great. The only problem with the inside stove is that the smoke will have a tendency to fill the room until a person learns how to cope by partially opening the wood feed door prior to opening the door wide so that the draft gets started.

matt_man · #39 12/09/10, 07:13 PM

Quote:

Originally Posted by 6e

Your house sounds like our setup. About the same size and all. My main concern is that our house is on a concrete slab and all duct work is in the ceiling. So, that creates a bit of a problem about how to get the water lines to the furnace since going under the slab isn't an option. I was thinking about running the lines up the side of the house, through the attic and down to the furnace, but it would have to be SUPER well insulated to keep from losing too much heat. Thoughts?

We have a new house, which we built, but we didn't have any ductwork. A/C and a furnace were an afterthought. We do luckily have a crawlspace so we were able to cut a hole through the concrete stem walls to run the pipe through. Then it had to run up to the attic area where they put the heat exchanger in. All our ductwork is also in the ceilings.

The pex for our unit is in 8" foam insulation. Take that into consideration. I don't think it would be wise to just run it up the outside of the house. I think that it would be too cold and you will loose a lot of heat that way. It wouldn't run very efficiently. Enclosing it inside a casing with extra insulation would help, I'm sure.

**Ross** · #40 12/09/10, 10:10 PM

My lines are buried deep and are well drained in insulated PEX (Ecoflex) but they would freeze if left uncirculating for too long.