Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: Mr. Maple on August 25, 2014, 10:14:57 AM
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Had a salesman in this morning, took me around to existing customers of his. He told me my problem with the present boiler(Empyre 450) is too small a water jacket to keep up with demand. We are feeding heat to two farmhouses, running two different directions from the boiler. He likened it to a family function, big pot of stew on the stove , running low, just add a bit of water, and some scraps and you can continue serving, versus small pot of stew, run out and have to start from scratch. It makes sense to me, not sure how much our Taco pumps pump through per hour, he said the damper would cycle a lot less, burning less fuel with a larger water jacket. On the flip side of the coin,from what I have read a smaller water jacket heats up faster, but will it be able to keep up as well once the demand is put there from two houses?
Thanks for your help
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That does sound like a salesman, a boiler compared to a pot of stew is one I've never heard till now ::)
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Sounds like somebody has been partaking before 4:20 to me, more water does not create more heat period.
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Maybe he was talking about more water for his 4:20 instrument. :)
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Seriously guys, think of extra water storage like a larger battery on your old truck, if the alternator does not put out enough amperage to carry the load, then the larger battery does no good, the extra water is for when you have more heat than you can presently use and it is stored in the battery/tank
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Less water is more efficient. Quicker recovery time, less burn time..No brainer..It takes less energy to heat 50 gallons of water than heating 100 gallons..As long at the boiler is sized up to heat whatever you desire..Should not be a problem..
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Less water is more efficient. Quicker recovery time, less burn time..No brainer..It takes less energy to heat 50 gallons of water than heating 100 gallons..As long at the boiler is sized up to heat whatever you desire..Should not be a problem..
Don't tell Garn that.
You'll have shorter burn times with less water but more of them. With less water you also don't have near as much leeway to refill the with wood either if you should be detained by overtime at work or whatever.
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Less water is more efficient. Quicker recovery time, less burn time..No brainer..It takes less energy to heat 50 gallons of water than heating 100 gallons..As long at the boiler is sized up to heat whatever you desire..Should not be a problem..
Don't tell Garn that.
You'll have shorter burn times with less water but more of them. With less water you also don't have near as much leeway to refill the with wood either if you should be detained by overtime at work or whatever.
That fine..Ill call my neighbor to fill it... ;D ..I think everyone that owns a OWB, when running has a plan or who to call to fill the boiler....People call me..
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I am curious about not having the bigger water storage. Seems like I will have to watch how much wood there is in the stove so it won't go out.
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Slim is so right on the money, more water doesn't equal more heat output.
More water will help with
-less burn cycles (if for some reason you want that).
-the ability to have multiple heating systems come on at once without "shocking" the system and causing water temps to drop quickly.
What more water capacity will not help with is
-more total heat output.
-more efficiency ( unless you are using a system like Garn that uses a different burn time concept then traditional outdoor furnaces).
If your problem is that the furnace can not keep up with demand increased water capacity does little to help. What would do you a lot more good is a furnace with a larger firebox. This would do two things, increase the amount of BTU's the furnace could generate and also increase the amount of BTU's that could be absorbed into the water jacket.
In other words a firebox has a certain amount of sq inches of space to exchange heat into a water jacket. Increasing the amount of water around the same size of firebox doesn't increase that exchange rate. Adding water doesn't make the fire burn hotter or the heat to move more quickly from the firebox to the water jacket. A bigger firebox does both. Of course a bigger firebox would need a larger water jacket to work properly.
In the example given by the salesman he says its like a pot of stew. Add water and serve more people? But in the end you are serving a poorer product because there is less actual nutrition. Its actually a fairly good analogy of why his theory is wrong. More water doesn't make better stew or a better furnace.
I would seriously consider not buying anything from a salesman who knows so little about how a furnace operates. There is no possible way water can increase BTU's, storage just doesn't do that (unless we are talking huge amounts that is heated during the day when demand is low). I would highly recommend finding a local dealer who understands how these systems work. If you don't I'm afraid you may waste more money. Good luck
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what do you think about thermal storage tanks then.
some places on the net rave at the benifits of stoage tank saying it adds bulk to your system
you still need so many gallons to heat a certain amount of space.
if not,wouldn`t the boiler yoyo when heat is required.
i always thought more water meant less up and down and a more even running system
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You are right Duke! Thermal storage is more like a big buffering tank, it stabilizes the load but it still takes lots of heat to get the tank hot and then there is the added load of heat loss at the tank. Storage tanks work well for batch burning or where there is a very large load all of a sudden like in a greenhouse application where the stove is dormant all day and as soon as the sun goes down you need everything that the stove can provide, this is where the tank can be used to store heat during day allowing the stove to stay hot by dumping the heat into the tank
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I completely agree with Slim (as always)! There is a time and place for large storage. The problems that a normal situation involving an outdoor furnace is the heat loss and the refiring of the furnace after all the stored heat is used. On a normal outdoor furnace hooked to a home the large storage isn't necessary and would just be a nuisance. Greenhouses, dairy barns, some commercial buildings ect are examples where heat load may fluctuate greatly and heat storage may be beneficial.
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All I can tell you is that my system has 400 gal. of water. I'm heating house and basement and a 1500 sq.ft. shop. When the house calls for heat, I loose 12 degrees in temperature as the heat is pulled out of the water on the way back to the boiler. Now if the water in the boiler is running at 175 degrees it don't pull the boiler water down 12 degrees. I watched the boiler temp. and only lost 2 degrees after about 5 minutes of heat being pulled out of the water. It takes a lot of a long time to cool down before the boiler kicks in. Everybody has there onion on more or less water in the boiler jacket. I have a buddy who believes less is better, but he is always refilling with more wood because he is using up the smaller amount of water. He does have a quicker recovery time but is refilling more often. Let's try this. Put 2 identical pots on the stove, one with 1 qt. of water and the other with 3 qt. of water heat to almost a boil. Turn off the burner and leave pot on hot burner. Which one will cool down quicker. The air temp. pulling the heat out of the water, and the burner being the heat source. It takes longer for the 3 qt. pot to cool down than the 1 qt. Everybody has there onion on which is better. Small water jacket or large. I prefer the larger jacket.
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But the part you are missing is the added fuel it takes to heat the 3 quart pan vs the one quart pan and the added heat loss from the surface area of the larger pan, believe me there are places where extra thermal storage is a good idea, huge amounts of water surrounding a wood fire is not one of those
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If your just heating a smaller home thats pretty well insulated, a smaller water volume would work fine. When I'm done between the wood boiler and waste oil boiler I'll have almost 700 gallons of water. Plan is in the shoulder seasons heat all that water with the waste oil, get it up to temp and shut it off for the day. Between feeding cows, hauling hay, plowing snow and what not we might go weeks at a time and not even spend ten minutes a day in the shop, but when we do need it, want to get it warm now, which where the large amount of hot water will come into play.
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Just talked to a CB dealer in my area last week. He told me he was at the CB plant and seen every kind of boiler made in there plant. They check each and everyone to look at the good points and bad. He could sell a block of ice to an Eskimo. Almost had me convince in a CB. He installs too. They have a large water jacket. The larger the sq. ft you are heating the larger the water jacket. I just don't like all the electronics on the CB. The simpler the better. I use a Taco 0011 in each building and he told me that was a waste, a 007 is all I need to run the system. I know this is not true. There are a lot of things to consider. He said it would pump to 15 ft. But did not tell you that you loose volume. At 15 ft. you are only pumping about 1-2 gal. of water.
My 0011 will pump 34 gal,/min and the higher the head the less water until you get to around 34 ft. I would rather keep the water moving than only getting around 1-2 gal,/min. out of the 007. I know everybody don't agree, but if it works don't fix it. Every salesman will tell you that there OWB are the best on the market. It's up the the individual to get all the fax's from a plumber before he make a decision on what is best for his setup.
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i`m glad i got this storage part going.why you say.
last year i saw some talk on hear about the boiler buddy.
i would never pay for one but i had an old water heater so i tied it in.
to my suprise it did help even as primitive as it was.
now i`m no expert but full burn for twelve hours,not sure
but heat from the wood for six and lots of coals to keep the heat there.yup
i live in southern canada so -20--30 is often.so it chews up wood no matter what you heat with
we are gone 14 hours a day.80 or so gallons is not enough.
when its really cold the blower can start alot
and it seemed with more water i was able to keep the water up to temp longer after the wood was gone
have not decided what i will do yet but all the discusion sure helps.
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Slimjim
I'm aware it does take more to get the boiler up to operating temp. I start my boiler early in the fall and make sure everything is working. It sometimes takes me 2 days to get it up to the 175 degrees that is preset at the factory, I can't adjust my temp. I start it up slow, using small sticks and wood that would not be much good to burn in the winter. I believe a slow start up is easier on the boiler.You don't want to start up a boiler with a roaring fire. Once the water is up to the 175 it don't take a lot of wood to keep it at that temp. I'm not restarting the boiler every time the temp drops, it only drops to 170 degrees and then it kicks in. I'm glad everybody has and onion on thick firebox, stainless verses steel, and large water jacket verses small jacket. Whatever your preference, you do have a choice. If it weren't for different choices we would all be driving the Henry Ford car. Same goes for boilers, we have a choice, and everyone has an opinion on what is the best way to go. Maybe if I had a boiler with a small water jacket from the start, I would prefer that over the large one I have now.
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Water jacket size alone has zero bearing on efficiency.
The calculation requires water volume AND wood volume in cubic feet. And this only gives you a total btu output, NOT a btu per hour figure.
This is where your max GPM flow and lbs of fuel per hour come into play, divided by the net firebox volume over lbs of fuel per hour, yields max btu per hour output at full burn.
Many homebrew stoves learn this the hard way, if they didn't use available formulas specific to wood stoves to figure this out.
Feeding two houses with any Empyre is a daunting feat, unless you don't mind constant monitoring and feeding.
Any water volume can be made to work as long as the fuel consumed per hour can be made to match the demand.
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I've got to beg to differ with you on the Empyre's Sprinter.
A friend of mine EASILY heats his 2500 sq. ft. home plus his 15600 CUBIC ft. shop (30'x40'x13') with a Pro Series 400.
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woodbutcher, how many gals does your cl400 hold. I didn't realize central made a small firebox/large water jacket furnace.
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"The calculation requires water volume AND wood volume in cubic feet. And this only gives you a total btu output, NOT a btu per hour figure.
This is where your max GPM flow and lbs of fuel per hour come into play, divided by the net firebox volume over lbs of fuel per hour, yields max btu per hour output at full burn."
Sprinter-if I am calculating right then a CB EClassic 3200 firebox is 40x48x30, which translates to 57,600 cu. inches correct?If I divide the 410 gallon water jacket into this figure I come up with 140.49, or is there a factor I have missed or done wrong?
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yoderheating
You got to remember my CB is 15 years old. When I bought it has a large firebox and holds 400 gal. of water. CB had the bright idea that putting the air intake for the firebox on the side of the boiler. They called it the cyclone air. It works but the wood on the opposite side of the air intake don't burn to good. It didn't take CB to put the air intake back on the door where the original had it. My firebox can hold a lot of wood. One winter we went away for the weekend and the temp. by day got to 30 and down to 20 at night with a 10-15 mph wind. I filled the firebox as much as I could get in. After we got home I was sure the boiler was out. Had the house set at 70 degrees. When I opened the boiler door I couldn't believe my eyes. I had lots of wood left. The boiler went 4 days before I had to add wood.
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SIZE OF WATER STORAGE
On furnaces without forced air draft this is a major consideration. Heating of the water takes a long time and it is important that a steady supply is always present. Small tanks in units without forced air draft just don’t hold enough hot water between burn cycles. Extra in-house storage tanks can be added. In forced air models the replacement of hot water is very quick and efficient. Unburned wood in a forced air system will instantly produce heat when the draft fan kicks on. These systems are more efficient and burn less wood. However there still needs to be sufficient water around the firebox to reduce the number of burn cycles. Even on small furnaces having forced air systems the absolute minimum for efficiency is 125 gallons capacity, increasing to 300 gallons on large furnaces.
Taken from http://www.outdoorwoodfurnaces.org/guide.php (http://www.outdoorwoodfurnaces.org/guide.php)
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125 to 300 gal is not a lot of water storage.
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this debate could go on forever,but i've seen a farmer in northern vermont who had a 160 range boiler outside and he said he had 1000 gallong reserve in his basement.did take a long time to get up to temp but when it was up there it took very little wood to maintain that temp.he would heat his house,two garages and a shed.he ran it 365 days a year for hot water for the hot water in the house and in his dairy barn.who knows
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It's not how big it is, it's how you use it. ::) ;)
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hehehe!!!!! :thumbup:
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Good one Crow!
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Normally when people talk about large water capacity they are talking about three times the gal of water per 1,000 btu's. For example a Empyre 450 has 300 gal of water and a similar size furnace by Taylor has 800 gal.
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I"m curious about a few things, everyone seems to just be comparing water gallons, not really how the heat is distributed, so my question is, how can you compare only water gallons in the boiler, and not really worrying about things like, say for example, one boiler is hooked to a heat exchanger radiator where a fan blows through it, and another is hooked solely to infloor heat in the concrete floor of a shop or basement, wouldn't the infloor heat have more thero storage as some call it, than the one with just a radiator/fan setup or doesn't that factor into any of the equation?
Then don't things like piping distance's, total footage of piping and lastly how well insulated the heated building is, all factor into that equation somewhere.
In theory, won't a small water jacket, and large water jacket use the same amount of wood to heat the save given space, once the water's hot and you discount the wasted heat at the end of the heating season, if these are taken out of the equation isn't about the only thing left things like burn times and temp fluctuation.
Then when do things like efficiency come into play, how is furnace efficiency calculated?
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Dirtdigger, you are somewhat correct about the size of the water and the application it feeds are related.
So let me break this down to the best of my understanding, and others can argue if they want.
Adding a larger water jack to a OWB does not necessarily increase any of the following: Efficiency, heat output or length of burn time. What the larger volume does do is to help reduce the shocks (hot or cold) to water temperatures to you boiler. But by adding a large volume of water you are also increasing the start-up timeof the system, because you will have to get the entire water jacket up to temp before you can ever start trying to pull heat off of it to heat structure.
**Point in case -> old man runs a CB eClassic 2400 (340g water jacket), CB requires a thermostat bypass valve (when water temperatures below 140f come out of boiler it gets returned, above 140-165 some is returned some is allowed thru to HX or radiant application, above 165f water go straight thru to HX or radiant). So in the fall when he fires up OWB he has to heat up 340g of water above 140, then it finally makes it to HX & Mixing valve before going out into the slab (4000sf). It can take up to a day or two to get the whole slab up to temperature, if my dad is not payign attention and gets the fire light a little late