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How many hours per week do you burn?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Nofossil, Dec 14, 2007.

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  1. Nofossil

    Nofossil Moderator Emeritus

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    There's been some discussion about boiler sizing, and I'm feeling a bit defensive since mine is so small compared to everyone else. Boilers, folks - get your mind out of the gutter!

    Part of my theory is that big enough is good, but bigger isn't always better. I sat down with a glass of good bourbon and crunched the numbers for my last heating season from October 21 through April 14.

    My boiler was burning (defined as a water jacket temperature above 140 degrees) for an average of 51 hours per week, with a maximum of 86 hours.

    That works out to an average of 7 1/2 hours per day and a peak of 12 1/2 hours per day.

    It burned for a total of 1282 hours, and burned 4.5 cords of wood.

    It's an EKO 25, which is rated at 80,000 BTU/hr. By my calculation, it actually produced an average of 63,000 BTU/hr and 18,000,000 BTU/cord.

    The time between fires is determined by the size of the storage tank. If I had a larger boiler, I think I would have had more fires, but each one would have been shorter. Does that make sense? How does this pattern compare with what other people are doing?

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  2. Tarmsolo60

    Tarmsolo60 Feeling the Heat

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    I just got my storage hooked up about a week ago and haven't really looked at any hard numbers. I would say 6-9 hours a day, I start a fire about 5pm and depending on the state of the tank and the house demand i'll reload what I think they need to be satisfied around 10pm, then repeat the next day around 5pm. we've has some cold nights already but we will see -20 to -30's before winter is over my hours will definatley go up. I've got a hearthstone heritage soapstone woodstove on order for our great room that i'll run on really cold nights so that should make my tank last like it is now during much colder weather.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    Right now I'm running mine more or less like I ran my old Royall conventional boiler. Since I don't have storage, I never fill it all the way up, so we're talking about a series of smaller fires. Presumably, as I outlined in another thread with a similar thrust, this is far less efficient than less frequent loadings and longer burns. So on days when I work from home, I'm still going out there every 3 or 4 hours and tossing in a couple of chunks. But there's a huge difference. With the old boiler, I made smaller, hotter fires to try to keep the smoke down. The price for that was less heat available to the house, so you had to "stage" the zone pumps if you wanted to get the whole house warm, and that only worked when the temps outside were in the teens or warmer. Now I use basically the same approach because the place would overheat if I put more wood in. So you're talking a much higher level of comfort for the same amount of effort or less, and much more flexibility and utility when the temps drop to near zero.

    If you want to get into who's got a bigger one, heat load-wise, then obviously I'm you're guy. I'm sure I could get away with a Model 40, but down the road I have big plans for that greenhouse, and where the 60 is going to make a big difference. And I just might expand the tank to 2,500 gallons. So I'm happy.

    If I ever get as efficient as you, nofossil, I'll be able to heat my neighbor's pool--all winter long--and still have a warm house and fresh produce.
  4. Jim Post

    Jim Post Member

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    I don't have storage. I been running my tarm 24/7...since October 9th this season. It's a Solo Plus 30 which is rated at 100,000 btuh. Heat loss on our house rings in at 78,000 btuh so we are slightly oversized but adding in the side arm hot water heater gets us closer. Typically I load the boiler for an 8hr burn based on the weather forecast. The boiler cycles a draft fan to control the fire. To get the actual burn time it would be nice to log the time that the draft fan is on. For now, I am quite happy with a 6 to 10 hour loading schedule. Last year we went through 6 cords of wood but we were keeping the house much warmer...75 -80 degrees typically. This year our thermostats are set @ 66 and the house is coasting around 70 degrees. Our wood consumption/ash production is much reduced.
  5. solo40

    solo40 New Member

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    I have been running my Tarm solo 40 24/7. I have only had the Tarm installed for 6 weeks. Next year I hope to
    add some water storage.

    Ethan
  6. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    That's absolutely correct. The size of the boiler with a storage tank system determines how fast you can re-heat the tank after the heat zones deplete it.

    There's a minimum "steady-state" size for the boiler, at which it would just keep up with the heat loss, and not have anything to spare. Beyond that, anything extra is just for convenience of having fewer, faster burns.

    Of course, if the design of the storage tank and heat exchanger limits your re-heat capacity, it doesn't matter how big the boiler is - it won't heat the tank any faster than that heat exchanger can dump the heat into the water. Over-sizing the boiler beyond that amount will end up making it idle, and avoiding idling is half the reason to install a tank.

    A good "sanity check" is to measure the baseboards in the house (or whatever else is used for heating the house). Calculate the actual maximum amount that the heat emitters can deliver. Often, the oil or gas boiler may be grossly oversized in comparison to that number. It can't dump heat into the house by being a bigger boiler. The heat is actually delivered by the baseboards/radiant/forced air/whatever, and that determines the minimum boiler size. The boiler may be larger than that, in order to provide rapid recovery of the domestic hot water tank, which typically results in a 100kbtu minimum boiler sizing.

    Joe
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    Welcome to the Boiler Room, solo40. Nice to have someone from North Hero, and another Tarm user, on the board. Or, onboard.

    Glad to hear it's working out.
  8. Nofossil

    Nofossil Moderator Emeritus

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    Actually, I'm thinking that with a larger boiler I'd have to have more fires. I don't want to idle the boiler ever. My reasoning is this: I build a fire and keep it going until everything including the tank is at temp. Then I live off the tank until it's depleted - say 12 hours. Those two times added together determine how often I have to build a fire. The less time that it takes to heat my tank, the less total time per cycle.

    If my boiler was just exactly matched to my heat loss for the house, I'd build one fire and burn 24/7. If I could live off the tank for 12 hours and I had a billion BTU boiler, I'd have to build two very short fires per day. The bigger the boiler, the more often I have to build a fire.

    That's my reasoning. Am I nuts?

    My situation precisely. My baseboards can only absorb 30,000 BTU/hr, but my oil boiler was sized at 120,000 BTU to provide rapid hot water recovery.
  9. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    That was for an ideal situation, with a heat exchanger sized to dump it all.

    In other words, if you had an over-sized boiler, and a tank heat exchanger that could accept that amount of heat, you could do one burn to get the tank up to temp, and then run off that.

    Also, I was thinking more in terms of "time spent burning" rather than "number of individual fires" when I said that. I really don't mind lighting the fires. MAPP torches tend to simplify that procedure :)

    Joe
  10. bbb123

    bbb123 New Member

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    I have a digital scale I'm gona use and weigh the wood I burn and see what effiecientcy I'm getting. I usually burn mine in the morning 1-2 loads depending on tank temp. Thats when its warm though last night it was in teens so I had to have a fire. Until last night I've been goin to bed with tank around 150-160, no fire, turn down the heat to 62 downstairs 68 upstairs and tank would be 140-150 in morning.
  11. Seyiwmz

    Seyiwmz Member

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    Greetings fellow gasifiers. I currently burn 24/7 for about 2 weeks at a time. I can only do this when the weather is sufficiently cold enough to allow me too. Otherwise my system goes into overheat once and a while. That means I can only burn for about the 3 or 4 months of the coldest part of winter. I still end up burning about 1000 gallons of propane a year before and after. I'd like to eliminate that. I have space for a 5 x 5 x 5 cube tank. I was thinking about using 10 guage steel and building myself. It would be pressurized like the rest of the system. I was wondering if anybody else built there own tank out of this guage steel and had success or failure? I been burning an Eko 40 for about 3 years. This is the first year I been burning strictly popple/aspen, small round wood 5 or 6 inches and similiar split sized. My friends and neighbors were non-believers, telling me I wouldn't get any heat from that "junk" wood. The normal person looking at my wood pile would see the punky dried up scavanged popple and laugh. But I tell ya what, it's gasified great. After 10 straight days burning, I finally cleanded the bottom of ashes. It filled half of a 5 gallon bucket. I usually get 3 or 4 times that much with maple. So I'm pleased. I can't wait to build my tank so I can gasify at a harder rate. I don't know if anybody else has smoke problems when they stoke their stove, but I built a hood above my stove with an exhaust fan. That was the answer. I turn it on before I open the door, then the smoke is sucked right up the hood. I don't bother opening the stove damper at all, just throw in the wood load, turn off the fan and walk away for another 10 hours. Good Luck
  12. Nofossil

    Nofossil Moderator Emeritus

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    You burn an EKO 40 24/7 and also use 1000 gallons of propane - you must be heating something enormous! How much wood do you go through in a year, and what are you heating with it?

    I also burn a lot of 'junk' wood. Most of what I have comes from wood lot maintenance. As long as it's dry, it burns. I get a lot more ashes per burn hour, though.

    I'd be concerned about pressurizing a square / cube tank, though I'll admit to zero actual knowledge.
  13. Seyiwmz

    Seyiwmz Member

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    Actually, the house is smaller, approx. 2000 square feet. But terribly insulated, I have to clean attic and blow some in. The walls are only 4 inches. The garage the stove is located has decent insulation, about 28 x28. It stays above 60 most of the time just from radiant heat off the Eko. So, I need to insulate, need a tank, and burn 12 face cords in about 3 or 4 months. Thanks,
  14. Eric Johnson

    Eric Johnson Mod Emeritus

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    Welcome to the Boiler Room, Seyiwmz. The UP is one of my favorite places. Ski and sauna--you can't beat that.

    One of our members here who has an EKO 40 had pretty good luck blocking off part of the nozzle during warm weather. That allowed him to fire the boiler hard, but produce fewer btus per hour. Presumably he got longer burns.

    Have you considered trying that? You can block off part of the nozzle with a piece of firebrick, and probably not even have to fool with the air controls.

    I have the EKO 60, which has two nozzles. I had pretty good luck just blocking off one nozzle and running it that way. I think it effectively cut my heat production in half.

    I'm not really clear on what happens when you go into "overheat" mode. Doesn't your blower just shut off and the boiler go into idle?

    Details, man. We need details!
  15. Seyiwmz

    Seyiwmz Member

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    I have 3 zones in my house. Normally, there is at least 1 that's drawing heat. But if it's kinda warm out and none of the zones are taking any water, I'm screwed. The boiler comes up to temp. shutting down the fans, but enough heat is being produced that the water temp hits around 220 or 230 and the pop-off valve lets the hot water out the emergency drain to the outside. Instant Sauna for the outdoors. I have an aquastat opening up one of the zones, but it's usually too late by then. That's an interesting idea about blocking off one of the nozzles. I kinda wanna try it on my next fire up just to see what happens. Thanks.
  16. Jim Post

    Jim Post Member

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    Wow...blowing your relief valve on a regular bases doesn't seem like the best way to operate a boiler. I have my tarm piped/wired so that if the temp continues to rise after the zones are satisfied and the draft fan shuts off, the biggest zone will come back on and dissipate the heat regardless of the wall thermostat setting. In three years of operation this very seldom happens as the fire quiets down pretty quickly once the draft fan shuts off. Another way to use that extra heat would be to pipe in a sidearm water heater to heat your domestic hot water.
  17. Nofossil

    Nofossil Moderator Emeritus

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    On my blower, there's a sliding gate that restricts the air inlet. If you have it, I'd play with that first. I think it would have the effect of reducing the output of your boiler, so it would heat (and overheat) more slowly, and burn longer on the same load.

    My controller plays all sorts of games to direct heat to different places, but the second aquastat forcing open a heating zone sounds like a simple and great idea.
  18. Eric Johnson

    Eric Johnson Mod Emeritus

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    Do you make small fires on warm days, Sey? That's what I do.
  19. mikeyny

    mikeyny Feeling the Heat

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    I have an old tarm, vintage 1982, a 3000 sq ft. + house built in the 70's (1870's that is). Very little insulation, drafty with high ceilings. My fairly new nat. gas boiler is 225,000 btu and heats the place to any temp you want in any weather. ( I never NEVER, USE IT). My tarm is rated at 110,00 btu. no storage. At 20 to 30 degree weather I make a fire at 6 am reload at 730 am and go to work, 530 pm house is cool 58. Make a fire, reload at about 7 or 8pm and at 6 am house is again cool, 58. I keep it at 62 during the day and 65 at nite. 4 yrs ago I used 12 cord, each yr I learn a little more how to conserve and I am now down to about 7 cords plus a good pile or two of construction debris early and late in the season. My gas bill for heat and hot water runs about 2 to 400 bucks per winter season here in upstate ny. In cold weather I restoke later at nite and earlier in the morn. I believe all wood boilers should be undersized to take advantage of the efficiency of a full throttle burn. A big benifit of this is that there is virtually NO smoke. I have also learned that it takes several seasons of operation to learn how to use each individual unit effectively. Undersize ,UNDERSIZE, UNDERSIZE!!!!!! Also I have a good handfull of healthy kids to help out with wood and no wife to bi%$$#@ about it being too cool in the house. Life is great.
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