Help with wood boiler

Eagle26 Posted By Eagle26, Oct 10, 2018 at 6:20 PM

  1. Eagle26

    Eagle26
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    Oct 10, 2018
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    Hi all, I really don't know much about boilers, but was hoping I could get some advice for my unique situation. I moved into a place a couple of years ago that came with a Buderus Logano G201 wood/coal boiler. The previous owner told me he burned coal in it, and that worked great, but I have access to free firewood so I wanted to burn that. I did not get a good burn time because of the small firebox, and there were a few times it blew the pressure valve and steam started coming out. I'm thinking adding a storage tank would help with that, and getting a boiler designed for burning wood may have a larger firebox and help with burn time? Is that my best bet? Currently, the boiler is in my garage and the pipes run up to my propane furnace and the coil is up by the blower on the furnace. There is no water tank, so I was wondering if I really need one? I am on a very limited budget, so a new gasification or outdoor unit isn't an option. My goal is to get a used wood boiler for the same or less than I could sell my current boiler for (anyone know the value of those?) and simply swap them out. Maybe add a storage tank? I was looking at an older Glenwood 950 boiler... is that a decent option? Any tips are appreciated! Thanks!
     
  2. Fred61

    Fred61
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    I have a good used wood gasifier I'll sell you along with a 500 gallon storage tank. Where are you at? I see you have a ? in your location column.
     
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  3. maple1

    maple1
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    What do you mean by not good burn time exactly? Long burn times don't really go good with boilers. That usually means smoldering & dirty burning & wasted wood. They are way different than a stove or furnace - you are working with a liquid cooled fire box.

    No matter what though it shouldn't blow off - you have an issue there of some sort. Could be a pressure regulator/fresh feed issue, or an expansion tank issue (waterlogged?).

    I think you would be hard pressed to find a used boiler that would do much better than that one, unless you find a gasifier (maybe hook up with Fred above?). Or one that has heat exchange tubes. That you can easily keep clean. If you are hoping to find one for less $$ than you can get for yours - well, good luck. I spent 17 years with a Benjamin that had similar size firebox and less efficient heat transfer design than the Buderus - it was a big struggle but it did heat our house, with the oil cutting in the odd time. Storage would have done me no good at all, but it might help you - it all depends if the boiler can put out more heat than your house needs over the burn time. If so, you could add storage to capture that heat then use it when the fire goes out. My old one had all it could handle just keeping our house warm at full honk.

    Is the boiler clean? Is your wood dry? Do you have lots?

    I don't know anything about Glenwood, but the brochure I just found with Google is loaded with misinformation. Which may mean nothing about the boiler you are looking at, just don't know....
     
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  4. peakbagger

    peakbagger
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    I have a wood/coal boiler. The buderus boiler you have has the reputation of being a nice piece of equipment. The firebox isnt huge but I expect that is not the issue. There are a lot of issues that you need to understand before you make a plan to resolve them and the bummer is that learning hot to runa boiler without storage is a lot harder in the fall. I am not familiar with your boiler but it looks pretty standard https://www.bosch-climate.us/files/G201_Install6720618151-01_US.pdf

    I am worried about your saying that you popped the safety. This should never happen unless someone installed it incorrectly. There should be a dump zone on the boiler. The manual has installations with optional dump zones and other without them. A dump zone is usually an external radiator or a zone of the house that cannot be valved off. If the boiler goes over a high setpoint it should start pumping hot water to the dump zone to get rid of excess heat. This setpoint is usually set a few degrees higher than the air control so in an overheat situation the air damper closes to cut down on the fire and if there is just too much fuel and air leaking in the dump zone valve will open and send heat to the dump zone even if the thermostat is not calling for heat. The safety relief valve is just there to keep the boiler from exploding if the water starts to boil and exceeds the pressure rating of the castings. Definitely not good!. In My Opinion a dump zone is not optional unless there is some other fool proof method of getting rid of heat when there is no demand from the heating system. The other reason for dump zone is if the power goes out. That means the circulator pumps stop running and the heat had nowhere to go. The air damper control appears to be thermal so it will still close the air damper on overheat but that may not be enough.

    First thing to learn is the boiler really only wants to run flat out full bore where all the heat is being pulled away as soon as its produced. There is primitive control of the output by cutting off the air supply but when you do that you are creating lots of creosote and air pollution. A rough way to think about is controlling the speed of car engine by stuffing a rag in the air cleaner. Ideally you want to match the amount of wood in the firebox so that the air control is always open. The problem is that the heating demands vary depending on the thermostat zones so you may be cranking along fine while you are heating up the house but once it warms up you go from needing heat to not needing heat for awhile. Meanwhile you have a full firebox and warm boiler so the choice is overheat the boiler and pop a safety or the air controller closes the air flapper (same as stuffing a rag down an air cleaner) and hopefully starves the fire for air and puts it out. The air flaps are typically not air tight and depending on how hot the fire was, enough air may be leaking in to keep enough burning going that the safety pops. Not a good situation.

    Now add some water storage to the system. The storage is a big heat load that can take hours to warm up. In this situation the boiler is going to run for hours with steady of demand for heat. Therefore the air control stays wide open and all the heat is taken away to the storage tank. This means you are getting good combustion so no creosote generation or dirty smoke to the neighborhood. The trade off is you need to feed the boiler on occasion to keep the fire going while you are heating up the storage. With a small fire box that can be every 20 minutes while you are heating the storage. As the storage warms up you need to keep an eye on the storage temperature, as the storage warms up to its maximum temperature (it ranges but it has to stay below boiling and may be lower if you have a liner) you need to time adding wood so you run out before the tank goes over the maximum. If you time it wrong, the boiler is running full bore when the storage goes over its high temp and there is nowhere for the heat to go. This means the air flap closes and maybe the dump zone opens up.

    Once the storage system is heated up the heat for the house is supplied from the storage for many hours dependent on how much of heat load there is and how much water there is in the tank. Realize most homes have slant fin type baseboard radiators and they are designed for fialry hot water, usually over 140 F. They still put out some heat with lower temps but most homes are designed for hotter water to reduce the amount of baseboard. Therefore once the storage gets down to 140 F its time to fire off the boiler again. So the trade off is with storage you need to pay attention to the wood boiler more often for 2 or 3 hours and then ignore it for a day or two depending on heat load. If you try to just run it without storage to meet the heating demand then you need to watch it constantly and live next to it on cold night or risk popping safeties.

    I have found few folks over the years who run strictly a wood boiler with no storage. The ones that do eat up a lot of wood, create plenty of acrid foul smelling smoke in the neighborhood and have creosote issues. I got my boiler for free and tried to do it without storage and decided the hassle was only worth the effort during really cold stretches when I was home. It wasnt until I put in storage that I stopped buying oil for my furnace 5 years ago.

    The other thing to realize is the fire typically goes dead out in between firings. Unlike a wood stove, there are rarely any coals that remain so you need to stock up on kindling as you will be relighting the boiler every time you need to heat, with storage that is every day or two. I start mine with just a few sticks of kindling and newspaper but I also have dry wood.

    It is a steep learning curve and every install is different so you need to spend time figuring out the piping going into an out of the boiler. If you spend the time and understand the trade offs you may be a wood burner. If you dont want the hassle just dont sell it for cheap as its nice unit that should sell for good bucks to the right person.
     
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  5. Eagle26

    Eagle26
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    Thanks for all the help guys! I’ll try to answer some of the questions and add some more info. First, I am from Pa, so Vermont is a little too far for me to drive. I was hoping to not have to start a fire every morning and every time I get home from work...maybe that’s not possible with a boiler? I have four young children and mornings are crazy for me trying to get them all ready and to the babysitter on time, so adding starting the boiler from scratch to my mornings makes a difference. I did have issues with creosote build up because I was trying to burn it slower so it wouldn’t go completely out. Would adding a storage tank help with that, or would the fire still go out and I would just get heat longer? Would a 50 gallon tank do anything or would I need to invest in a bigger one? Any other way I could get a 10 hour burn time and not have to start a new fire? Do I need to look a big outdoor unit for that? Or should I just keep the Buderus and burn coal? Also, I don’t believe I have a dump zone. I guess I need to figure something for that too
     
  6. peakbagger

    peakbagger
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    Assuming you do not have a crazy heating load, a storage tank would work great for getting your mornings back. I charge up the tank at night and dont need to restart it until the next evening in cold weather and sometimes 2 days in shoulder season.

    In order to determine what size storage you need and how long it will last requires heat load calculations or a way of measuring your heat load. There are roughly 8 pounds of water per gallon. A pound of water stores 1 Btu for every degree F its raised. Now you need to figure out the lowest temp water you can circulate (typically 140 degrees for standard baseboard and the highest temp the tank can be raised to. Pressurized tanks may make it to 200 F while un pressurized lined tanks are probably good for 185. I will use the 185. Now subtract 140 from 185 and you get a 45 degree delta T. So evry gallon can store 360 btus. Now multiply the tank volume by how many gallons. So a 500 gallon tank will hold 180,000 Btus. That sounds like a lot but one gallon of heating oil yields about 110,000 Btus. So if you use 1 gallon of oil per day, a 500 gallon tank will supply a days worth of heat. A cubic foot of gas yields around 850 Btu so do the math. In theory there is a nameplate on the wood boiler with its rating. It probably is around 100,000 Btu per hour. So you now need to run the boiler for a couple of hours to heat the tank up.

    I dont see you getting a long burn time and with children in the house I sure wouldnt want to smoulder a coal fire all day.
     
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  7. maple1

    maple1
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    50 gallons won't help much. I have 660 and would like more. Half that might get you thru half a day?
     
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  8. Eagle26

    Eagle26
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    Thanks for the info... maybe my best bet would be to save up for a gasification unit? It sounds like I would need at least a 500 gallon tank to store a days worth of heat. But even though that will store the heat, the fire would still go out and I would need to restart it right? So even if I get a wood boiler with a bigger firebox and large storage tank, I would still need to feed the fire pretty often to prevent creosote build up due to a slow burn, is that right? Not sure if there is a good solution for me, but I was just hoping to be able to burn wood without having to restart a fire every day
     
  9. peakbagger

    peakbagger
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    No way to do slow burn even with gasifier. A coal boiler has a bottom grate and unless you have crappy draft a restart does not take long. I put down a couple squares of cardboard in the middle of the bottom grate and about five sticks of kindling on top of it, then a few smaller splits of wood on top of the kindling and then one or two quarter logs on top of that. I save up newspapers and roll them in tube and put them in the undergrate area and light them with match and walk away. In about 10 minutes the fire is roaring and then I add a few larger splits to the fire box.

    The big advantage with a bottom grate is it burns the wood down to fine ash. No lumps of unburnt wood just fine ash
     
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  10. Eagle26

    Eagle26
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    Good point peakbagger, my Buderus does have the bottom grate and it burns down nicely. I just grew up with a regular wood stove and we were always able to get the fire going easily with the red hot coals in the morning. Thought it seemed dumb to have to start a fire every morning and evening after work. It does start fairly easily though, so maybe I should just keep the Buderus.
     

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