Woodmaster 3300 or 4400?

[KRB64]

I've been contemplating an OWB for several years now (if I'd bought one when I started it would have already paid for itself ). I've also been searching for somewhere that compares the various brands/types/configs/etc, etc with no luck. As an ag extension agent I like to have fact based research to make decisions but take what I can get... I finally stumbled upon this site and have been reading various searches voraciously and am tickled to death to read the opinions and insights offered opcorn: . I regularly use a Cummins diesel and Dodge Power Wagon forum and they are a wealth of information.

Now, my questions: I think I've decided on a Woodmaster for its simplicity and stoutness. But am torn between a 3300 (up to 2,000ft2 & ~80,000btu) or the 4400 (5,000ft2 & ~ 175,000btu). My house is 100yrs+ with marginal insulation and about 1,500ft2 currently heated with a 4ton 100,000btu propane forced air unit with an old Vermont Castings to take the edge off.

I'm leaning towards the 4400 but am concerned that it would be idling too much? I'd love to add radiant floor someday or even a shop that would double the ft2 but realistically and financially that will probably never happen. Based on yourall's knowledge and experience is the 4400 too big or the 3300 too small?

Is the heat exchanger thrown into the existing duct work as simple as they make it out to be or will it compromise the propane that I plan to use as a backup? It has a squirrel cage with no pulley to change the cfm. I plan to use the aquastat tied into my existing thermostat. I plan on the hot water plate too.

What about the piping? Seems like everyone is stongly biased to either urecon or microflex and its a toss up? :deadhorse:

Seems like I have other questions too but I've droned on long enough. Again, thanks for the site and all its insite!

 

[zsteinmetz]

In your case i would definately get the 4400. Bigger is better in an owb case and it will require less fills also. I have a Wood Doctor and love it. My house and garage combined is about 3000 sq ft and I was also on the fence on what size to get a 4000 or 8000 sq ft model. I got the 8000 and am glad i did. Wood Doctor has a formula on sizing they say add your total square footage you will be heating and multiply it by 1.5 and thats what size boiler to get. You dont want to get one too small and be out there three times a day filling it.

The heat exchanger is a breeze. Just make sure you have about four inches on top of your a coil and cut your hole and slide it in. I used some steel shingles on the ends and bent them to make an air tight seal followed by good foil tape.

I bought the foam insulated pipe from a local pipe supplier. It looks like a drainage tile filled with flexible foam. Easay to work with and about $7 a foot.

Congrats and good luck!!!

 

[Butch(OH)]

You can quit searching for unbiased comparisons of OWBs on the net, there aint any. Of course I think you have made a wise choice since I own a Woodmaster myself I am heating about the same footage in a 1945 fair/good insulated home and my 24x22 well insulated workshop with a 4400 and don't believe Id want smaller, not because of BTU output but because I need the burn times offered by the bigger box. The boiler would heat twice what I am heating easily. I am forced air heated also and have unscientifically tested air flows with the heat exchanger in and out of the plenum and cant tell the difference.. Still I put it on a set of rails and can slide it out in the summer so the A/C doesnt have to work any harder than needed. The OWB aqua stat controls the temps in the circulating water only. Your home thermo will control the blower in your furnace only. There is no connection between the two, pumps run all the time. My pet peeve with Woodmaster is the thermostat instructions S:censored: k big time and questions will be answered like "have a local HVAC guy help". I think liability causes this? Anyway my furnace has the fan like yours, they are multi speed (most are anyway especially if you have A/C too). If you have a "fan on" circuit in on your current thermostat the hook up is dead easy. More info the the type of control on your current furnace will get you help on here when you get to that point.

 

[KRB64]

The heat exchanger is a breeze. Just make sure you have about four inches on top of your a coil and cut your hole and slide it in. I used some steel shingles on the ends and bent them to make an air tight seal followed by good foil tape.

So the duct needs to be 4" taller that the coil itself?

Thanks for the info, I was thinking bigger IS better but wanted confirmation from someone other than the seller...

 

[zsteinmetz]

Yes four inches at a minimum five would be perfect. If you have an access into the ductwork to actually see where the a coil ends that is best. Otherwise drill a small hole and look in.

 

[flashy]

central boiler.

Have you looked into getting a Central Boiler OWB? The firebox of a CB is designed to keep more heat. Go on their website and look at the comparison page they have. It makes alot of sense that a rear smoke discharge loses less heat than a top discharge. Also, they are better insulated. Fiberglass batts vs polyurethane spray on. After a light snowfall a CB roof will be white a lot longer than a Woodmaster roof. I looked at both before I got the CB. Thought forced draft would be better, but now I know it is totally unnecessary. Ash auger? Why? All I do for ash removal is use a long handle shovel every other weekend after I let the fire burn down just a little on a nice day. There isn't much ash anyway. The simpler, the better, I always thought. CB outsells Woodmaster by about 20 - 1 around here.

 

[KRB64]

I'd looked at a CB, and they seem to get good reports here too but I like the round fire box. Plus I have local WM dealer and that makes me feel better. Mind not totaly made up yet. Haven't priced the CB either. Will the ripple top collect deposits and fill up eventually?

Good to hear that the furnace blower should be fine. The WM dealer said that I could wire the aquastat into the thermo wiring and that would kick the blower on at the desired temp? Then the house would heat before the thermo said to fire the propane. Makes sense to me but I can barely wire a 3-way switch..

Can the metal shop that fabs ducts make the slider rail for exchanger removal? I have AC too and may want to "summerize".

 

[Butch(OH)]

I'd looked at a CB, and they seem to get good reports here too but I like the round fire box. Plus I have local WM dealer and that makes me feel better. Mind not totaly made up yet. Haven't priced the CB either. Will the ripple top collect deposits and fill up eventually?

Good to hear that the furnace blower should be fine. The WM dealer said that I could wire the aquastat into the thermo wiring and that would kick the blower on at the desired temp? Then the house would heat before the thermo said to fire the propane. Makes sense to me but I can barely wire a 3-way switch..

Can the metal shop that fabs ducts make the slider rail for exchanger removal? I have AC too and may want to "summerize".

RE: thermostat and aquastat wiring.
I guess you need to explain your needs some more or you dont understand how the system works?

The boiler and controls are TOTALLY seperate of your home heating needs. In other words, if disconnected from your house the OWB will heat up to the selected temp and maintain it as long as fuel is present. You then tap into this heat via the circulating water. The pumps MUST run all the time, at least on a Woodmaster. So the coil in your ductwork is warm all of the time. The heat in your home is controlled by turning the blower on when the temp is below your selected temp, off when it reaches the temp. The way I did my control is I added a second thermostat (#2 from here on for brevity) in the house that is simply wired in series with the "fan on" feature on my gas furnace thermostat (#1 thermostat) . To use the heat from the Woodmaster. I set the #2 at the desired temp and place the "Fan On" switch on #1 to "run". The gas furnace thermostat (#2 remember? LOL) is set 5 degrees below #1 so the gas furnace may act as a back up. In reading this I know is is long winded but I could show you how it works in a minute, harder for me to explain here, sorry. The rails I made for sliding my heat exchanger in and out are simply hardware store angle iron pop rivited to my plenum sides. My dealer, who has sold hundreds has never done this, they just leave the heat exchanger in line all the time. The side in and out feature of mine is probably not worth messing with if you have to pay someone to make and install it.

my 4400.

<IMG SRC=http://i8.tinypic.com/2uhwq37.jpg>

 

[infomet]

I may be silly jumping in here when I don't own an OWB, but I've read a lot and have some control design experience, so here goes.

Holding constant temp in the OWB wastes "quite a bit" of fuel. It's best burning fairly hard and putting stored heat into a tank of water. Do you have a place to put 500-1000 gallons of storage? With no storage, efficiency is gained by letting the furnace idle until more heat is needed than is stored in the idling furnace and water. So if you set up to control the furnace based upon the house demand you can save some wood. In this case, your house thermostat would call for heat and the circulator pump would start. In mild weather, the house would warm, just on the slow fire and stored warm water in the jacket. In colder weather, you'd then want the OWB draft to open or draft blower to start, heating the system and the house.

Now the harder part. As the OWB temp came up, you'd start warming the house. To be tricky, you'd anticipate the warming of the house and close the OWB draft well before the house thermostat was satisfied. Then you'd finish off the house with the heat stored in the OWB as it warmed. Ideally the house thermostat would shut off and the OWB would be back down close to its idle temp. (controlled by the aquastat) at about the same time.

The reason for this is that losses in the system rise rapidly as the temp. difference between the OWB and the underground pipe increase. Conduction loss, like from buried pipe to the ground, is fairly linear (depends upon temp. difference), but radiation losses, like from the warm OWB to the air, are worse (going up as some power of the T difference). I'm no thermodynamicist, but radiation is a great way to lose heat!

Running the pump continually just keeps the loss to the ground high and the radiation maximized!

Radiation is a problem for the storage tank, obviously, so it must be well insulated. All the worse because you'll want the storage to run hot enough to store a half day or so worth of heat! It would be wonderful to have an OWB with it's door to the outside and its body in the house/shop/basement. Then lots of the losses mentioned would be to the heated space, thus raising overall efficiency.

The big unit loaded once a day is great, especially if you have a long winter (I forget where you are.), but idling is relatively inefficient and you'll get smoke on startup. You would probably use less wood with a smaller OWB, if you can accept some extra loading during your worst weather.

Your interest level and the ease with which you can get wood will affect what you do, but a little design work can probably make a 25% difference in consumption, maybe somewhat more!

You can get most or all your domestic hot water from the OWB system when it's running, which is worth $50/month or so, depending largely upon how many showering people ar at home and whether you do much laundry in hot water.

There's quite a bit of this talk in the archives of the Google woodheat gtoup.

Keep us posted on your planning, please,

 

[Butch(OH)]

I may be silly jumping in here when I don't own an OWB, but I've read a lot and have some control design experience, so here goes.

Holding constant temp in the OWB wastes "quite a bit" of fuel. It's best burning fairly hard and putting stored heat into a tank of water. Do you have a place to put 500-1000 gallons of storage? With no storage, efficiency is gained by letting the furnace idle until more heat is needed than is stored in the idling furnace and water. So if you set up to control the furnace based upon the house demand you can save some wood. In this case, your house thermostat would call for heat and the circulator pump would start. In mild weather, the house would warm, just on the slow fire and stored warm water in the jacket. In colder weather, you'd then want the OWB draft to open or draft blower to start, heating the system and the house.

Now the harder part. As the OWB temp came up, you'd start warming the house. To be tricky, you'd anticipate the warming of the house and close the OWB draft well before the house thermostat was satisfied. Then you'd finish off the house with the heat stored in the OWB as it warmed. Ideally the house thermostat would shut off and the OWB would be back down close to its idle temp. (controlled by the aquastat) at about the same time.

The reason for this is that losses in the system rise rapidly as the temp. difference between the OWB and the underground pipe increase. Conduction loss, like from buried pipe to the ground, is fairly linear (depends upon temp. difference), but radiation losses, like from the warm OWB to the air, are worse (going up as some power of the T difference). I'm no thermodynamicist, but radiation is a great way to lose heat!

Running the pump continually just keeps the loss to the ground high and the radiation maximized!

Radiation is a problem for the storage tank, obviously, so it must be well insulated. All the worse because you'll want the storage to run hot enough to store a half day or so worth of heat! It would be wonderful to have an OWB with it's door to the outside and its body in the house/shop/basement. Then lots of the losses mentioned would be to the heated space, thus raising overall efficiency.

The big unit loaded once a day is great, especially if you have a long winter (I forget where you are.), but idling is relatively inefficient and you'll get smoke on startup. You would probably use less wood with a smaller OWB, if you can accept some extra loading during your worst weather.

Your interest level and the ease with which you can get wood will affect what you do, but a little design work can probably make a 25% difference in consumption, maybe somewhat more!

You can get most or all your domestic hot water from the OWB system when it's running, which is worth $50/month or so, depending largely upon how many showering people ar at home and whether you do much laundry in hot water.

There's quite a bit of this talk in the archives of the Google woodheat gtoup.

Keep us posted on your planning, please,

Interesting reading. Not owning an OWB doesn't cause me to disqualify an educated or experienced opinion. I am no engineer and have no HVAC experience other than wood stoves and changing furnace filters so people may take my "knowledge" with proper caution.

In the case of a Woodmaster it is required that the pumps run all the time there is a fire in the box. I didn't feel the need to ask why? All other OWBs that I am aware of with the exception of Hardy run that way, again I don't know why. As for losses associated with the pipe we are in total agreement there. I read on several postings where people with fuel consumption problems had "tested?" the pipes for loss and found "very little" loss because they were "only" loosing 3-5 degrees between the stove and house. Taco says my 011 could be pumping up to 25 GPM. 3-5 degrees out of 25 GPM is a heck of a lot of heat!!, I don't think many people realize that. My loss is less than 1 degree in 60 feet, my meter doesn't register any finer than a degree. Also in my (short, 1 year) experience with my OWB it requires almost no fuel to maintain temp when nothing is being drawn from it. Guessing that half a wheel barrow load would keep it to temp for a week with the circulators running. Mine is set to burn at 160 and shut off at 170. I know in warm weather, 50-70, in the spring that it took 3-4 days to cool down to warm to the touch when it ran out of fuel. I think most of the heat loss is the door which heats the outside air full time?
My system does use some fuel, no doubt about it. But I attribute that to the fact that I demand a lot of heat from it, the fact that the door heats the outside full time and the inefficiencies inside the firebox, not from maintaining temp or circulating the water.

 

[HEAVY FUEL]

Get the 4400

I spent the extra $1500 and got the wood master 5500. For the extra money I have twice the heating capacity (10,000 sq ft).I have a 36x60 shop I heat along with the house. I've never met any one around here saying they wish they had gotten a smaller owb. It's always the other way around. I let both pumps run continuous because they don't use much electricity. From what I've gathered it's the frequent starts that will take out the bigger pumps.opcorn:

 

[KRB64]

"RE: thermostat and aquastat wiring.
I guess you need to explain your needs some more or you dont understand how the system works?"

Hmmm, now that you've spelled it out you are right. The dealer said that there were two ways to "hook it up". One was like you said and add a second thermostat that is set to come on before the back up propane. The other way was to use only the existing but somehow tap into the wiring but now that you are making me think about it I can't tell you how it was supposed to work (late night and alcohol don't help any either...). I'll have to ask him to explain that one again.

So, what exactly is an aquastat or what does it do?

Infomet, you make a lot of sense. I have a friend with a Tarn that is adding in I think a 500 gallon "heat sink" for storage. The extra water cap of the larger size is what I was thinking would be an advantage for me but didn't know if that would be canceled out by having the fire idle longer?

BTW, my friend with the Tarn says I'm crazy to buy the Woodmaster. He (an engineer) says that its a big inefficient beast. That I need to wait for the next generation of high efficiency gasification boilers. He already talked me out of a good end of the season deal on last year's model .

 

[ktm250rider]

The wooddoctor Converter is supposed to be an increased efficiency boiler. Havent seen much info on it. Gonna try to get out and see one this week.

 

[hockeypuck]

Freeheat machine

Freeheat machine also has some new generation boilers, but I am plenty happy with the 4400.

 

[carney19]

I just installed my 4400

Just got done last week installing a 4400. It was pretty simple and as for my application:

1750 sq ft. Main level
1750 sq ft. Basement
All new construction w/ forced air propane on top and in floor heat in basement.
I also have it hooked up to the water heater so that never has to run and I have virtually infinite hot water...the wife loves that! I am biased since I work at woodmaster but I absolutly love it so far. We had a cold spell here last week where the temp reached 32 degrees and my house was toasty and the propane isn't even hooked up. Anyways just thought I would throw in my two cents.

 

[HUSKYMAN]

I am in the process of installing a 4400 now, I am going to be heating a 1700 sq ft house and a 1600 sq ft barn. I just poured the concrete in the barn with the hoses last weekend and should be getting the boiler in about three weeks.

My main reason for getting a Woodmaster is my dealer, he has been helpful so far and is going to come over and help me install the boiler for free.

 

[logger450]

I have a 3300 and absolutely hate it. I have heard good things about the 4400. Saving up to upgrade. Don't want a gasser but I might have to .

 

[midwest_170]

What's the price on the 4400?

 

[logger450]

I see them for around $7000