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System Update Advice Needed

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by GreenMonastery, Apr 16, 2010.

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  1. GreenMonastery

    GreenMonastery New Member

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    Hello everyone,

    I have been browsing this site for the past 2 weeks as we have been researching the best options for a system upgrade to our current heating system. I was hoping for some specific advice about our system and would appreciate any feedback anyone can offer.

    We are a Buddhist monastery located in Southern BC Canada - we currently heat our 10,000 sq ft main building, 2,000 sq ft outbuilding (of which only 700 sq is heated) and our DHW (with a propane back-up) with a Heatmor 150k btu OWB. The unit has been installed for the past 9 years and has worked exceptionally well for us. The prime motivation in replacing it is to use less wood (currently use 28-30 cords/year), smaller sized wood (currently load 4' rounds - all beetle kill pine) and increase overall efficiency.

    We are looking at the Econoburn Outdoor model (EBW-200-O) as all the infrastructure is set up to place the boiler outside and we're not really keen on building another shed as there is already a wood shed right next to it that holds about 30 cords. The Econoburn is also really appealing because a dealer (who I believe is on this site) is just an hour away and I have had very good dealings with him thus far - via e-mail. We are still undecided about storage for our particular needs - is there any efficiency advantage to adding storage for our application, or is it more a matter of convenience? We would need to place the storage outside as there is no room in the house and re-plumbing the existing system inside would be a major undertaking.

    The heat comes into the house (about a 50 ft run) into 2 plate hx - one going to the 2 lower floors, in-slab (basement 6" concrete with styrofoam insulation, second floor 1 1/2" concrete) and the other hx going to upstairs radiant baseboard with the DHW coil branching off first. A line branches off the main line at the boiler and goes to the outbuilding which runs directly through radiant baseboards.

    During the coldest winter days we require an average of 2.5 million btu's/day to keep the buildings at 70. We are currently increasing attic insulation up to R90, adding triple cell blinds to windows that need to open and removable SIP panels on the outside of windows that don't need to open during the winter months. All of which will hopefully bring our btu demand down.

    Our cir pumps are low wattage 'El-Sid's' which were bought because we are 'off-gird' and produce all our own power (80% through solar - 20% through a diesel generator in the dark winter months, all run through Trace Inverters and an 80 kWh AGM battery bank). Energy use is a major factor in determining anything we do here, we currently have our daily demand down to 10 kWh's/day...and falling!

    Hopefully this basic info can elicit some feedback and advice from the community here.

    Thank you in advance.

    Dhammavaro Bhikkhu
    www.birken.ca

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  2. Nofossil

    Nofossil Moderator Emeritus

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    Another monastery with a wood gasifier - this is an interesting trend! See this thread.

    With the heat load that you're looking at, you'd need a LOT of storage to make much of a difference. In my experience, storage is more about convenience in firing schedules than it is about efficiency. I expect that with a concrete slab, you could let the fire go out for a while even without storage on warmer days.

    In order to do the math, we'll need to know the lowest usable temperature for your radiant heat. My guess is that you'd need around 2000 gallons of pressurized storage to sustain your heat load for a reasonable amount of time.
  3. GreenMonastery

    GreenMonastery New Member

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    Hi nofossil,

    Thank you for your comments and the link to Father John's posting - I saw it several days ago and also thought it quite interesting! As an aside - our sister monastery in Northern California just installed a Tarm for a new building on their property; simplicity, sufficiency and sustainability are 'hallmarks' of monastic life and gasification is another step in that direction, as far as externals are concerned.

    A little more information about our heat load - we were doing the math over breakfast this morning - with our added insulation, on the coldest winter days, we will probably be looking at needing 1.5 million btu/day. This is our requirement for about 100 days of the year, the rest of the time our demand is quite low (well, compared to 1.5 million) probably 1/3 in the shoulder seasons with no heat required for the summer months. We were thinking of 1,000 gal of un-pressurized storage which won't do much for the winter but would be more than adequate for the other 200 days. There is always someone on site here so loading the stove several times a day is not an issue for us.

    The lowest usable temp for our baseboards is about 140 F and about 90 F for the slab.

    We have found over the years that even on the coldest winter days if the fire goes out the house can sustain itself for nearly 12 hours without feeling any decrease in temperature - so...storage is, as we conceive it, for the shoulder seasons and for DHW in the summer with the thought of adding hot water panels in the near future.

    Look forward to more input. Deep thanks for the help!
  4. Nofossil

    Nofossil Moderator Emeritus

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    When referring to an affiliated monastery, I'd think it would be a 'brother' rather than a 'sister' monastery ;-)

    A general rule of thumb is that your average daily heat load is about half of the peak load. I don't know about the Econoburn, but I think most gasifiers will deliver about 75% of their rated output as a good average. If the EB 200 is a 200KBTU/hr unit, that would be about 3.6 million BTU per day running continuously.

    If you used pressurized storage with a working temp range of 90 to 180 °F, that would give you about 750,000 btu of heat storage, or enough for about 14 hours on an average winter day. Doing the math, the EB200 running for 10 hours should give you about 1,500,000 BTU, so that works out quite nicely. However, you'll need pretty warm days in order to skip with only 750,000 BTU of storage.

    If you have the space, 2000 gallons would do you a lot more good.

    I love the combination of DHW from wood in the winter and solar in the summer. Since DHW uses a LOT less energy, consider dividing up your storage so that you only have to heat a portion with solar. If you could do four 500 gallon tanks and heat just one of them with solar, that would likely work well.
  5. GreenMonastery

    GreenMonastery New Member

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    nofossil,

    Thank you for this information. We've taken your advice to heart and we are quite certain that we want 2000 gal of pressurized storage (just one message and we shift from 830 gals of unpressurized storage - quite the digital influence you have ). :)

    Can you share the math that calculates the amount of btu's we will get from this set-up? The temp range I'm thinking of is 140-190 as our baseboards work poorly below that.
    A few other questions - How large of a expansion tank would we need? If we go pressurized does that eliminate the need for a hx in the tank itself - does the boiler run directly into the tanks? As well, does that eliminate the need for the hx that takes the heat to the baseboards (as it is also a pressurized loop)? Can the storage tank run directly into the pipes in the house (obviously not the in-floor because we need to drop the temp to run through the concrete).

    Many thanks.
  6. GreenMonastery

    GreenMonastery New Member

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    I've been reading around for the past several hours and seem to have answered most of my questions re: storage.

    Still hoping that you could share your math on the btu calculations. Was your estimate of 750,000 btu storage based on 1000 gals?
  7. Piker

    Piker Minister of Fire

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    (2000 gallons) x (90° delta T) x (8.3 Btu's per gallon) = 1,494,000 Btu's stored in your tanks.

    1.5 million Btu's per day = approx 62,000 Btu's per hour AVERAGE... leaving at most 100k Btu/hr (average) or so left to dump into storage if you keep the fire in the upper chamber stoked. On a cold winter day to cover both the load and to charge the tanks, your looking at 15 hrs to charge the tanks. Since you probably have people around to tend the fire, this would probably be acceptable. The storage would then carry you another 24 hours.

    I ran an EBW200 for two seasons. That boiler will devour a load of wood in 4.5 hours running full bore, but to keep the output up on the coldest days when you may need it, you may need to tend the fire every 2 hours or so if you wanted to max out the tanks. Don't forget, however, that with a delta T that works down to 90°, if you don't get the tanks up all the way to 180, it's not too big a deal... just fire it up again the next day and take it up from there. Sounds like you might have a plan that will work for you.

    Personally, my experience with DHW has been quite different from nofossils... the 60k btu per day does not work for our family. The 4 of us go through about half a million btu's every 4 days, so we're about twice that at say around 120,000 btu's per day. This coincides with the roughly $80 cost reduction in our monthly electric bill when we use the wood boiler for DHW. (120,000 Btu's = about 35 kw-hrs per day @ $.09/Kw-hr). While our usage (wastefulness??) is twice what nofossil experiences, its still relatively small in comparison to the heat load on a cold winter day.

    good luck
    cheers.
  8. WoodNotOil

    WoodNotOil Minister of Fire

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    It sounds like you have well insulated structures and since you already have a wood boiler, you have a pretty good idea of how the system operates at various temperatures. This is a great advantage since most people only know how their system operates at the 180* their fossil boiler delivers. You could set your entire system up pressurized and eliminate any need for heat exchangers or you could keep the existing hx's in place so that you don't have the cost of altering them. You will need a fairly large expansion tank with 2000 gallons of heat storage, but you will not need expensive heat exchangers. I like Nofo's suggestion to use 500 gallon tanks and plumb them in series. I think his storage calculations were based on 1000 gallons of storage.

    Another option to look at is a Garn which is a boiler/storage all in one. You could put it in your current outbuilding where you store all that wood, but you would have to tap into your existing lines and extend them to the building. It is unpressurized, so it would connect to your existing system with no alterations and not require the controls and extra pumps that having separate storage would. That may be an advantage for you with the need for low power consumption. Just a thought...
  9. Nofossil

    Nofossil Moderator Emeritus

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    I was assuming a usable temp range of 90 degrees to 180 degrees. If you're careful with stratification and plumbing, you can get that and still have usable temps for baseboard almost to the end (where your storage is a uniform 90 degrees or less). Here's how you do it:

    Plumb your heating zones so that the radiant uses water that has already passed through the baseboards. If you have enough radiant load, you can be drawing water from storage at 180, using it in the baseboards, taking the 160 degree water from the baseboards and mixing it with radiant return (at 70 or so) to feed the radiant with 90 degree water. What you're returning to storage is around 70 degrees.

    If you don't have enough radiant load, your return to storage temp will be higher. With the thermal mass that you have going for you, I think you'll still get pretty good system performance.

    By the way - my local scrap yard had four 500 gallon propane tanks that they were willing to sell for around $130 each. Perhaps you'll be as lucky....
  10. GreenMonastery

    GreenMonastery New Member

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    Thanks for all the input everyone!!

    Piker - Thank you for the math! Do you think going with the EBW-300-O would be a better decision? 300k btu output and a larger box might reduce the amount of stoking in a day...there is always someone on site - but not sure if we want them to have to feed the fire every 2 hours... Our DHW demand is actually quite low considering we can have up to 25 people staying here. In the summer months running our current OWB is a gross waste, as so we have just been heating the DWH with a propane hot water tank which is in-line with the tank that comes off the boiler - at a fairly minimal expense. However, we would certainly like to get off the gas!

    WoodNotOil - you must have been developing your psychic powers of mind reading - I have been secretly coveting the Garn...The big selling feature with the Econoburn is that a dealer is just an hour away from us - very helpful man, we are going to see him next Monday. I just contacted Garn to see what a beast would cost delivered to our site...the idea of not needing more pumps is like music to our ears! We have been having more and more of a problem with our plate hx's as time goes on though - collecting grit (I think the SS water jacket around the boiler is rusting - or it might just be the anode rode depositing debris in our water) either way it is getting through the in-line filter we have and jamming up the hx's and I need to clean them out every 2 weeks to keep things working. The bonus of pressurized storage is that we could take these things out and have super hot water running to the baseboards...more decisions... :)

    nofossil - ok...wow...great idea about the baseboard loop feeing the slab!! Question occurs...what if the baseboards are not calling and the slab is? Our current system has a 'mixer' (for lack of the technical jargon) that mixes the return water from the slab with the supply for the slab to bring it down to 90 - brilliant to use the baseboard return though!

    Ah yes...storage tanks - this will be the deciding factor. I have my feelers out - the propane companies in our area will not sell their used tanks due to liability issues so the search continues...will phone the scrap yard once I finish typing this.

    Thanks again to you all - please keep the advice coming - this process is indeed rich.

    Be well,
  11. Piker

    Piker Minister of Fire

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    I personally do not have a problem going with a bigger boiler to put some muscle behind the thermal storage, and to increase the tank delta t per load of firewood (to a point obviously... a 1 million btu boiler hooked to 500 gallons of storage would be silly, yes?)... but if you can do what you need to do with 200,000 Btu's of output, then that's the size that I would recommend. Just be sure that you are confident with your heat loss numbers, and that the dealer is confident with the output rating of the boiler.

    I can't say for certain that you would need to load every two hours, as there are a lot of variables to consider; mostly wood species/density and moisture content. My guess is this would be a worst case scenario during the coldest part of the winter. And don't forget what I mentioned in regards to not taking the tanks all the way up to temp every time you fire. Just because the tanks at full charge can run your load for 24 hours doesn't mean they HAVE to. You have some flexibility.

    cheers
  12. Nofossil

    Nofossil Moderator Emeritus

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    No problem - just use a valve to provide bypass flow. The real problem is the other way around - what if the baseboards are calling for heat and the slab is not? Then, your return temps back to storage would be much higher than you'd like.
  13. heaterman

    heaterman Minister of Fire

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    Along with the excellent suggestions offered here so far, I would encourage you to explore the possibility of eliminating the baseboard heaters you have and installing some appropriately sized steel panel radiators in their place. When sized right, these will provide an excellent comfort level at reduced water temps. I have a combination of radiant floor and panel radiators in my own home and the water temperature in my boiler (gas fired) hit 155* a couple times this winter. Most of the time my boiler will run in the 120* to 130* range, less in the shoulder part of the heating season. You'll obtain far greater advantage from your storage if the system can utilize a wider temperature swing. 1000 gallons working with a 60 degree variation is equal to 2000 gallons that is constrained to a 30* drop. Yet another economy offered by low temp emitters.
  14. WoodNotOil

    WoodNotOil Minister of Fire

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    I think out of all of the options that a Garn does make the most sense in your application. They are very light on electricity demand and the controls are really simple and easily replaceable. It sounds like your hx's just need to be flushed out and then I would expect that they will work fine on the new install. With correctly place isolation valves and drain valves you could close both lines to the hx and flush it with a garden hose. It works really well when you run the water the opposite direction. As long as you keep the Garn at a usable temp, you will have heat and DHW year round with minimal elec. demand.

    BTW - no mind reading required, just a logical conclusion given you're off the grid and have a high heat load... ;)
  15. GreenMonastery

    GreenMonastery New Member

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    Thanks again to all!

    The exploration continues as our knowledge grows and costs are considered. Finding used propane tanks is proving to be not such a simple endeavour (pardon the 'u' it's a Canadian thing :) ) . A new set will run us about $7k - a bit out of our budget. So the thought occurs...

    Over the last 9 years with our present OWB we know that if the fire goes out, or there is some malfunction, on the coldest winter days that the house can maintain its heat for up to 12 hours without feeling any major difference in ambient temperature. This seems so mainly because of the massive amounts of concrete in the slabs. With the insulation we will be adding over the summer this should add hours to this 'window'. We also have 2 massive 'back-up' stoves in the house which can provide a great deal of heat in a pinch. We are now considering going without storage, for at least the first year, and see how it goes. Would love some feed-back. This will obviously not allow us to heat DHW via the boiler in the summer months, but this is the current set-up now and we might just wait until we install solar to achieve this goal.

    As an aside - all the monks here live in their own cabins - well, mini cottage. About 100 sq. ft. with a 30 sq. ft. sleeping loft, simple but beautifully finished - mine is heated by a HearthStone soapstone stove - yesterday was the first 24 hrs that I didn't need to have a fire. Our OWB is still going, may be until at least May... O Canada!

    piker- thanks! we know we get by quite well with a 150k btu boiler so the 200 should be just fine. The OWB we have does have a 150 gal water jacket though; the Econoburn has 42 gal available but I think with some thought into firing schedule that we should be quite well off...thoughts? All our wood is beetle-killed pine and the odd Douglas Fir that we can scrounge, all really well seasoned. What were you burning in your Econoburn to give you the burn time numbers you mentioned?

    woodnotoil - The Garn is still on my mind but I have not heard back from them and I actually have no idea how much a unit would cost, so I can't even begin to consider it a viable possibility...

    heaterman- The idea of low-heat radiators is good thought to consider; we won't be able to do it in this phase of the project but thank you for putting it in my mind.

    NoFo- (I saw someone else abbreviate your name that way - I have a secret love of abbreviating - hope I don't offend :) ) great point...I think we may just take out the hx's and run directly from the boiler and keep the system configured 'as is' since we know it works well enough - I really appreciate the innovative thought!
  16. Piker

    Piker Minister of Fire

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    The first season with the old boiler, we used a myriad of different wood species... from pine to hickory. A load of pine might go up in 2.5 or 3 hours running flat out. A full load of hickory might last 4.5 hours. Sometimes it's difficult to say how one boiler's output rating will compare to another's... you just don't know how the manufacturer arrived at their numbers... was the boiler tested for output, or was the ouput extrapolated from engineering specifications... if the output was actually measured, over how much of the bell shaped curve of the output graph was it measured... etc etc. Not being familar with the Heatmore unit that you have, I am aprehensive to say how the two will compare. I would think that you would be covered as far as output goes... it's just a matter of what kind of burn times you can live with if you don't install storage. With average firewood (20 to 22 million btus per cord) I wouldn't want the load to go much above half the rating of the boiler in order to get an 8 hour burn without storage. That's just a guideline... and guidelines in this industry are subject to an immense number of variables, which I am sure you are now well aware of.

    The 100 gallon difference between the two units isn't totally insignificant, but I wouldn't sweat it too much. If you wanted a hundred gallon buffer to help smooth the cycling of the boiler out, you could easily add a small tank to the system, though I probably wouldn't with the amount of concrete that you will be dumping heat into. When you fire the boiler, bump the temp up a few degrees in the concrete slab zones... at night when you need to extend the burn time, lower the thermostats in those zones and let the concrete carry you for a while. It won't be the same as thermal storage because concrete doesn't hold near the btu's per unit of volume that water can... but it will be helpful.

    cheers
  17. GreenMonastery

    GreenMonastery New Member

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    Thank you Piker - all this information is very helpful - re: the thermostat settings: that's what we were thinking about the larger swing temps at night. Do you know of any thermostats that can do this automatically that would easily replace our current, standard thermostats?

    p.s. - *best avatar on the whole site :) *
  18. willworkforwood

    willworkforwood Feeling the Heat

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    Welcome to the forum! The hydronics gurus have already given you lots of good advice on your system setup, but no one has mentioned wood quality yet, so I'll chip in my .02 on that. Econoburn, as with most gassers, function really well with dry wood, but efficiency slides downhill fast as the MC increases. But going beyond that basic requirement, the heat tubes in an Econoburn are virtually impossible to clean without disassembling the back plates and flue assembly. This means that if the tubes get coated with creosote and need to be cleaned, the boiler needs to be shut down and partially disassembled. Tubes coated with creosote will significantly reduce boiler efficiency. Two years ago, I tried to "stretch" my EBW through the Spring using poorly seasoned wood. The resulting creosote cleanup job of the tubes was a nightmare (trust me on that :sick: ). Lesson learned - this year I've had a full supply of well-seasoned wood and everything has been great.
    I see from your post that you are prepared to burn splits, even though you've been burning rounds in the OWB. I don't have any idea what the MC of your beetle kill pine might be, but stuff like this can be surprisingly wet inside, even when down for several years. I urge you to get an inexpensive MM, and split 20 or so rounds and get a good sampling. It's the center of the split wood that counts - that's your MC. If you find that your wood is not very close to 20% already, you will need to call out the troops and begin splitting and loose stacking asap. You will need to split in any case, but depending on the MC, you may need to split much smaller, in order to dry in time (mid August for you ? :lol: ) Having experienced both sides of this, I can't emphasize strongly enough how important dry wood is for an EBW - it's a wonderful thing when you feed it well! Good luck with your project!
  19. heaterman

    heaterman Minister of Fire

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    I would simply add that moisture content is a paramount concern for any gasser that is on the market, not just Econoburn. Also, one would have to shut any gasification boiler down to facilitate cleaning.

    If you have a gasser and expect it to function properly and up to its rated capability, you have to have properly seasoned wood. I can't put it any more plainly than that. It doesn't matter if you are running a Tarm, an EKO, Econoburn a Froling or even a Garn. If you want good performance and low maintenance, use dry wood. :)

    Companies and "salesmen" that claim their product has the ability to digest unseasoned wood do our entire industry a disservice. It's just flat out BS.
  20. GreenMonastery

    GreenMonastery New Member

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    Thank you very much for the advice on moisture content, we are picking up a MM in town today in fact. With our old OWB the thing smolders most of the time so we have never cared that much about it - we will now care :)

    willwork - any advice on running without storage? How is it working for you? Is it just a matter of knowing how much heat you will need and putting in the proper amount of wood so we're not smoldering all day? BTW - mid August is still summer here, we don't need to start the boiler until early September :lol:

    Many thanks!
  21. willworkforwood

    willworkforwood Feeling the Heat

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    Glad to see you are on board with seasoning the wood. Make sure to sample different areas of you wood piles to avoid skewing the testing. Thermal storage is established as the preferred way to go, as indicated by the many positive posts on this forum. I would have it too, just a bit outside of my budget right now, That being said, I've still been very happy with my boiler sans storage. You asked above: "Is it just a matter of knowing how much heat you will need and putting in the proper amount of wood". That hits the nail right on the head. Without storage you need to be planning 3 or more hours ahead. I'm always looking at the current and upcoming outdoor temp + wind + current indoor temp, to figure out what size fire should be going. The key is having the right circumstances, so that you can conveniently maintain the right sized fire. Someone away from their boiler all day will have a tough time with this. My wife is home while I'm at work, so this works great for us. With you manpower, it sounds like more frequent feeding would not be a big deal either. However, our boiler is in the basement, along with a huge supply of wood, so feeding, even in the middle of the night, is a nit. If your guys have to get dressed at 3 am, and take a 50' walk into a -25 wind chill, that might make for some new openings in the GreenMonestery :-/ . But you also said that you can go 12 hours from the slab alone. That would seem to offer lots of options to shut down the boiler for periods of time (do you do this now with the OWB?). Gassers work best when not idling (aka smoldering ;-) ), but with good, dry wood idling is not a problem - just less efficient. Less overall idling will normally result in less wood used. I think the bottom line here is that the EB (or other gasser) would not be that much different, with regard to storage, from your OWB; and there should be no reason you can't make it work well without storage.
  22. ken999

    ken999 New Member

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    If I may ask a rookie question...Where did the 8.3 Btu figure come from? Or better yet...what does it stand for? The amount of Btu's a gallon of water is capable of storing?
  23. Piker

    Piker Minister of Fire

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    There are plenty of thermostats that are programmable, either online or at the local home depot, lowes, or hardware store. You might spend $50 or so for a decent one.

    There was a comment earlier about cleaning the heat exchanger on the Econoburn. I know from experience that the heat exchanger on that unit is a bit harder to get at than some of the other equipment out there, and as was stated before, if you get it gummed up from idling a little too much, it makes cleaning a nightmare because the turbulators can sieze up. This would be true of any wood burning equipment that utilizes turbulators and enters into an idle mode for extended periods of time. There are units that do not come with turbulators in the heat exchanger for that reason... to compensate for the loss of thermal transfer they just increase the size and number of tubes. If you were to take the turbulators out of the Econoburn though, you would see a pretty good drop in thermal efficiency, as there are only 6 2" tubes to begin with.

    Don't get me wrong, you can still achieve good results without storage... but you really have to use your head. Keep the smallest - hottest fire possible that will maintain the demand, and the boiler will stay fairly clean. In short keep it gasifying, and try to modulate the ouput by metering the wood load during warmer weather. This will require frequent tending. If you're not going to put thermal storage in right now, I suggest making it part of the overall plan to eventually put some in. You just can't go wrong with a good heat storage system, and you'll definitely be glad you did. The only people who I have ever heard of that were dissatisfied with their heat storage were either people who's piping was out of whack, or the storage wasn't sized properly. Happiness is a heat storage tank.

    It still sounds like you've got a good plan and you're doing your homework... good luck

    cheers
  24. Hunderliggur

    Hunderliggur Minister of Fire

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    One British Thermal Unit is the amount of energy required to raise the temperature of one pound of water one degree Farenheight. There are 8.3 pounds of water in one gallon. I was a physics major so I just use 8lb/gallon - we leave the details to the engineers ;-)
  25. Piker

    Piker Minister of Fire

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    Water can store (or release) approximately 8.3 btus per gallon per degree of temperature change.

    cheers
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