Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: RSI on February 12, 2019, 11:13:48 PM
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Has anyone ever tracked wood usage and compared it to heating degree days? It would be interesting to see if wood usage for the rest of the season could be accurately estimated with it.
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I know right down to pound what I burned it's alot . 306,223,000 BTUs thru boiler. So far divide that in 1/2 thats BTUs to the houses. 6600sqft.
Now what's my heating days .. I will get back to ya .
Heat550
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https://www.degreedays.net/
Here's numbers your looking for .
Heat550
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37,398 BTUs per degree .. 4040 was my degrees days at average system at 63 degrees .. now how crazy is that number.
Heat550
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That says I need 7.38 bundles yet and I only have 7 left . That's with a DNR average of 7896 heating degrees days .. might have to get couple more bundles or cut up some nasty wet logs . 👍😎😉
Heat550
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How many here have only a certain type of wood with the same moisture content and soundness? I gave up on trying to establish a number since there are sections of pine, poplar, and cottonwood in the pile. Only thing I can say is my moisture content is consistent at 5-10% on all of it.
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For this season I have started logging wood use and daily high and low temps, and I will compare this to 2011/12, when I last ran a daily log just to see if anything has changed. It might give me some sense of the boilers performance- or maybe not.
I don't see how you can predict wood consumption as this would require an accurate weather forecast. I find the weatherman has become very good at forecasting one to three days out, and generally not bad a week out, much beyond that its a bit of a crap shoot. Last year, our March temperatures were "January like", and winter carried on well into April. No one foresaw that. For me, this easily added a half cord or more to my annual wood use.
Grease - How long has your wood aged to get the moisture to 5 - 10%.
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I advocate for measuring your wood consumption by the pound instead of by the cord. As long as the moisture content is consistent, when we are all talking pounds of wood consumption it doesn't really matter if we are burning poplar, pine, ash or oak. When you know your pounds per day and BTU efficiency per pound, we can all talk the same language.
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Heat550 - How did you calculate your BTU's needed per degree? Just divided the number of BTU's used (measured to date) by the Degree Days # (calculated to date)?
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Yep find your degrees days where you live. And the amount you burned.
So you can find out how many pounds it took for a degree . And also find the average degrees days at your location per season. DNR in Minnesota said 7896 for twin cities average degrees days per season.witch is about 3 degrees warmer then. Me .
Heat550
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Some good ideas here, need to find a good set of scales, maybe something I can deduct the tare weight and and walk over it during the load.
Grease - How long has your wood aged to get the moisture to 5 - 10%.
Between 3 and 4 years. Hopefully I don't outrun my buffer.
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For a scale I use a hanging scale used for meat carcasses with a large tub and hang it from the rafters of my wood shed.
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That says I need 7.38 bundles yet and I only have 7 left . That's with a DNR average of 7896 heating degrees days .. might have to get couple more bundles or cut up some nasty wet logs . 👍😎😉
Heat550
Have you checked a couple different points in the season to see if it is tracking with your numbers?
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I keep a track on how long the firewood rows last..Been doing that since I've owned owned OWB ( I did skip last yr lol)..Looking back on my lists, You can definitely tell if you've had a really cold winter or a mild winter.. Pretty neat Id say..
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Heat550- If I remember correctly you're closer to Duluth than the cities? If so, Duluth is a shake over 9000 if I remember correctly. I use 9000 in all my design, as "design day" here is only -17 and we both know that's laughable
Greasemonkoid- do you have to set an alarm every 3 hours or how do you keep up feeding that thing with 5-10% MC poplar and cotty? Holy crap
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When I switched from conventional to a gasifier I went as far as doing heat loss calculations on my house and 30x48 shed. I then took the btu requirements of the buildings, combined with the heating degree days of my area to come up with a total yearly btu requirement. Guestimating the stove running around 70℅ efficient, i could look up btu values of firewood and figure how many cords of wood per year I'd need.
Theres alot of variables at play here, but overall, i think my calculations have been pretty accurate. This is my 4 season with the upgraded stove. Warmer years I've came in just under what I guessed at. This year is much colder and ive kept the shed a bit warmer. So probably on pace to be a cord or two over this year.
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That seems like a lot of work.
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Greasemonkoid- do you have to set an alarm every 3 hours or how do you keep up feeding that thing with 5-10% MC poplar and cotty? Holy crap
No doubt that stuff wants to burn hot and quick, the flue temp controller cuts the blower when it hits 550*, it's plain to see whats burning because that light flashes when it's coasting back down. I definitely don't put much of that junk in before bed, it's not much shy of saw dust.
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I'm going look in to this closer . Because I think average degrees days for Minnesota has to have one mean swing . Closes weather station that has records for longest time comes to play . I'm right between Duluth and twin cities so I can average between the to. There the ones with oldest records. 8600 degrees days maybe . But that degrees days website pretty awesome. I got a weather station all set up so . Still need boiler data logger yet from RSI I'm getting there . Once I know boiler temp drop with weather temp . I can nail down my pounds of wood per degree right now Math is saying 8-9 pounds per degree .
That one polar vortex day math says 1250 lbs of oak slabs that's pretty dang close .
Heat550
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Math revisited... Ok Nov 16th 2018 to February 12th 7634.9 degrees days . Total wood burned 43,130 lbs so each degree takes 5.64 lbs of wood . Now I'm burning slabs 14-20% figuring 7100 BTUs per lb . 40,044 BTUs in to boiler per degree . So if I need 9000 degrees for total season. I need 7699.16 pounds yet that's 3.39 bundles now that sound like not enough .. so the issue will always be how many degrees days are there perseason . Kinda like a horoscope reader.
Heat550
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Cool. Using that site we can establish definitive bragging rights to see who has the highest degree days! My 12 month total is 10,317 at 63 Fahrenheit base temperature.
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You know when you open that can of worms there is a Canadian or Alaskan that's going make us look like a bunch wimps lol :bag:
2014 was some real degree days
Heat550
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I was just thinking another variable is heatloss in the ground. I would think that is somewhat constant throughout the heating season. That may be need to calculated separately.
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I found a better site weatherdatadepot.com to figure out heating degree days . Yes in ground heat loss is evil . I'm loosing 2.03 degrees in 274 feet in the ground 3 zones. This charts at 63f and just look how nasty 2013 and 2014 was.
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Using the Heating Season instead of Annual gives a better indication of the winter. For me it looks like 2013-2014 is the worst with 10,760.
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I like how you can really nail down the worst winter . It justifies why certain years took so much wood. Looking like 2018-2019 going to be for sure be in top 5 of last 20 years.
Heat550
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That heat loss in the ground is precisely why I've decided to put a plate exchanger in the back of the boiler cabinet and pressurize my underground lines with glycol with another pump in the house, so the underground only circulates on call for heat. Which, on sunny days, is never. If I can drop my circulation time from 24 hours to 12 hours, my math says that comes in at roughly 2 cord of wood saved per season. That's with Logstor
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That heat loss in the ground is precisely why I've decided to put a plate exchanger in the back of the boiler cabinet and pressurize my underground lines with glycol with another pump in the house, so the underground only circulates on call for heat. Which, on sunny days, is never. If I can drop my circulation time from 24 hours to 12 hours, my math says that comes in at roughly 2 cord of wood saved per season. That's with Logstor
That would be genius, how would you accomplish it?
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Great idea . But if it's loosing heat for the 12 hours you use it . Why not just Insul seal it and be done with it . I have 50 feet of Insul seal on one of my zones temp drop is undetectable . And a 130 foot run sprayed in polyurethane 4 inch on 3 side 10 inch on top with pex Al pex .looses about 1.2 degrees after 23 years in heavy clay . Other run I have is 110 feet looses 1.1 degrees after 23 years .. So story is you need 2-4 inch polyurethane and water tight once have that you can bring heat Los to minimum. I tested mine in winter . Not on hot summer day . Cold penetrates a lot better than everyone thinks. 👍😳 It's shocking .
I feel pretty lucky spray in polyurethane still hanging in there after 23 years . Back when I installed spray in polyurethane was cutting edge .
Heat550
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Braveblaster- I will have a 50 gallon water heater in the house as a buffer/storage tank with gas backup, also providing DHW, the tank has 2 sets of ports so I will hang a 40 plate exchanger and a pump between the spare 2 ports on constant circ with a Ranco controller regulating tank temp. When the tank falls below 130, the Ranco activates a pump to circulate the underground across both plates and reheat the tank to 160 at which point the underground stops flowing. On a call for heat, another pump will draw from the 40 plate in the house (same one used to heat the tank) and send hot water to the air handler. I've got all the parts here, just haven't had time to execute the plan yet.
Heat550- Because Insulseal would cost $6000 and take 100+ hours to complete, versus $600 and 8 hours, And my current ground loss is only 2.5 degrees in 350 feet with the Logstor. If I had it to do over again the first time, I'd spray it in the trench. But seeing as 50 feet of my Logstor is under a concrete slab and the boiler is on the far end of that slab, that's not an option now.
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Braveblaster- I will have a 50 gallon water heater in the house as a buffer/storage tank with gas backup, also providing DHW, the tank has 2 sets of ports so I will hang a 40 plate exchanger and a pump between the spare 2 ports on constant circ with a Ranco controller regulating tank temp. When the tank falls below 130, the Ranco activates a pump to circulate the underground across both plates and reheat the tank to 160 at which point the underground stops flowing. On a call for heat, another pump will draw from the 40 plate in the house (same one used to heat the tank) and send hot water to the air handler. I've got all the parts here, just haven't had time to execute the plan yet.
Heat550- Because Insulseal would cost $6000 and take 100+ hours to complete, versus $600 and 8 hours, And my current ground loss is only 2.5 degrees in 350 feet with the Logstor. If I had it to do over again the first time, I'd spray it in the trench. But seeing as 50 feet of my Logstor is under a concrete slab and the boiler is on the far end of that slab, that's not an option now.
That's a good idea. Always interesting/informative to see how guys get the most out of their system. A 2 cord a year savings is worth it if it means a Saturday or two just got freed up to do something other than cutting/splitting/handling wood.
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Braveblaster- I will have a 50 gallon water heater in the house as a buffer/storage tank with gas backup, also providing DHW, the tank has 2 sets of ports so I will hang a 40 plate exchanger and a pump between the spare 2 ports on constant circ with a Ranco controller regulating tank temp. When the tank falls below 130, the Ranco activates a pump to circulate the underground across both plates and reheat the tank to 160 at which point the underground stops flowing. On a call for heat, another pump will draw from the 40 plate in the house (same one used to heat the tank) and send hot water to the air handler. I've got all the parts here, just haven't had time to execute the plan yet.
Heat550- Because Insulseal would cost $6000 and take 100+ hours to complete, versus $600 and 8 hours, And my current ground loss is only 2.5 degrees in 350 feet with the Logstor. If I had it to do over again the first time, I'd spray it in the trench. But seeing as 50 feet of my Logstor is under a concrete slab and the boiler is on the far end of that slab, that's not an option now.
Indeed that is a good idea. I'm always learning from you guys, in case I'm blessed with my dream home later in life, will keep this foam trench in mind. Although, (I'm sure you are well aware of the exact heat draw on your unit) 14 gallons of 60 degree water for the first two minutes followed by 50 gallons of 130 degree water mixed with another 14 gallons of 60 degree water would suck the life out of my boiler on the bottom of the cycle. I remember you speaking of this a while back seems like, and where that delay-on timer came into play. It'll work out fine.
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Braveblaster- I will have a 50 gallon water heater in the house as a buffer/storage tank with gas backup, also providing DHW, the tank has 2 sets of ports so I will hang a 40 plate exchanger and a pump between the spare 2 ports on constant circ with a Ranco controller regulating tank temp. When the tank falls below 130, the Ranco activates a pump to circulate the underground across both plates and reheat the tank to 160 at which point the underground stops flowing. On a call for heat, another pump will draw from the 40 plate in the house (same one used to heat the tank) and send hot water to the air handler. I've got all the parts here, just haven't had time to execute the plan yet.
Heat550- Because Insulseal would cost $6000 and take 100+ hours to complete, versus $600 and 8 hours, And my current ground loss is only 2.5 degrees in 350 feet with the Logstor. If I had it to do over again the first time, I'd spray it in the trench. But seeing as 50 feet of my Logstor is under a concrete slab and the boiler is on the far end of that slab, that's not an option now.
Indeed that is a good idea. I'm always learning from you guys, in case I'm blessed with my dream home later in life, will keep this foam trench in mind. Although, (I'm sure you are well aware of the exact heat draw on your unit) 14 gallons of 60 degree water for the first two minutes followed by 50 gallons of 130 degree water mixed with another 14 gallons of 60 degree water would suck the life out of my boiler on the bottom of the cycle. I remember you speaking of this a while back seems like, and where that delay-on timer came into play. It'll work out fine.
Where are we getting these quantities and temps of water from? Bringing the initial 14 gallons that are underground up from 60 degrees to 160 (if that's what you were referring to, and if that's where the temp happens to be) is only 11,600 BTU over the 4 minute period, not much different than your average DHW load. I am still thinking of using a 3 way bypass valve on a 24V Ranco to divert the glycol back to the boiler until it's up to temp to avoid pulling heat out of the tank in order to preheat the glycol. Still pondering that, may require some R&D. I've been super busy this fall installing radiant systems on the side and doing 50+ at my real job, building a new shed at home and bought another rental house that needs a rehab too so this home stuff is kinda on the back burner lol. "some day" I'll get to it. House will be done next week and shed is to a "almost there" point, and my hospital job will be done tomorrow so I should have some spare time again soon! I'll keep you guys informed
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Here did more math nailed down my average per day 473 lbs a day keeping 6600 sqft at 63f . I did it like 4 different ways. Always came up 473 lbs .. I stuffed in 46,353 lbs so far .. it's like 165,000,000 BTUs to the buildings . I started with 400,000,000 BTUs of wood . Thinking houses take 200,000,000 BTUs . I'm going to run out early ... Yep .
Polar vortex pretty much screwed up my projections .