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Not bad numbers at all

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by heaterman, Apr 1, 2013.

  1. heaterman

    heaterman Minister of Fire

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    The picture is showing a reading of the flue gas coming from the BioWin260 pellet boiler I have running in my house. It has just about 900 hours of run time on it and has not been touched or cleaned at all. It has been through 200 on/off cycles as of tonight. Not too shabby in my book. I would expect that if I ran it through a cleaning cycle it might bump up a point or so but probably no more than that.
    The CO2 and O2 numbers are about what I would see on a decent running fuel oil furnace and are crowding actual real world numbers for high efficiency gas. Notice the dew point of the flue gas at 115*. This is why the boiler can run exhaust temps of 180-220* and not suffer any condensation problems.
    At the time this picture was taken the boiler was running at 45-50% output with a water temp of 158*.. I have never seen the efficiency numbers vary more than a couple points below to maybe a point above what the Testo is reading on the picture. Having stuck the "sniffer" in the stacks of all different kinds of wood burning equipment, numbers like this with that amount of hours on it is pretty impressive to see.
    Total pellet consumption during that run time is 2.38 tons.
    If you figure a ton of pellets at 16,500,000btu that tells me the boiler consumed an average of 43,633 btu per hour. It has been running since the second week in February.
    BioWin combustion #s 007 (1024x680).jpg Not

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  2. jebatty

    jebatty Minister of Fire

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    Progress is being made on many fronts. The days of the campfire in a barrel with a bucket on top, aka OWB, are and should be numbered -- innovation will keep wood in the forefront of efficient fuels.
    heaterman and Fred61 like this.
  3. arbutus

    arbutus Feeling the Heat

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    Hello,

    I'm curious what you figure the output into your house is - is the efficiency 86.6%?
    Also, if you don't mind, what are you paying per ton of pellets?

    Thanks,
    Jeff
  4. BadgerBoilerMN

    BadgerBoilerMN New Member

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    You had me until you compare best non-condensing combustion to "high efficiency gas". Still impressive and I will be looking into BioWin 260 for my next alternative energy, solid-fuel, residential boiler design. See a recent IBC condensing boiler installation we just commissioned here in Minneapolis.

    Attached Files:

  5. heaterman

    heaterman Minister of Fire

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    At 86.6% efficiency the actual average house load for that whole period was 37,786 btu's continuous. Not too bad for a house built in the 1920's. That's for all heating and domestic hot water use.

    The slick thing about this particular boiler is that it will modulate the burn rate to match what's going on in the house from about 28,000 up to just shy of 90,000 so it burns almost continuously. Most of the time the display would read between 40% to 65% firing rate, but on those nights we had that went well below 0* I would see it hitting 80 and 90% output. Only saw 100% a couple of times for brief periods. I have to say though that my heating system is tailor made for a variable output boiler because it consists of panel radiators with modulating valves which are always "on" rather than on/off like a forced air system.

    I've been using pellets from Michigan Wood Pellet up in Grayling and they seem to be pretty decent. Very little ash and quite uniform in density and size. There were no feed issues of any kind and I still haven't cleaned the ash container yet. I buy them for $189 per ton. So total heating cost for roughly 50 days of burning through the rugged part of this winter was about $400. That's probably around $200 less than I would have paid for natural gas over the same time period as our gas bill runs about $300 per month during January-March time frame.

    I really didn't think it would be less expensive than natural gas seeing how cheap that is right now but the ability to ramp the burn rate up and down makes a big difference. As I mentioned in the first post there are only 200 burner cycles showing on the boiler information screen. Most of these were due to the safety feature built into it which shuts down the burner every 6 hours to make sure nothing gets too hot and heat starts soaking into the pellet bin. Other than that, the boiler probably would just sit there and match its output to the house without ever shutting off.
  6. heaterman

    heaterman Minister of Fire

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    True. You can get a modern condensing boiler into the 90%+ range, but only if the system it's connected to is capable of dropping return water temps into the 100* range or less. That's possible only with a large mass radiant slab or a very carefully designed radiator system. In most cases though, a person has to work within the constraints of an existing system and that means return temps in the 130-160* range and resulting loss of efficiency. Most of the condensing boilers I see are running 86-90% when connected to a baseboard or forced air system. No condensation occurs under those circumstances because the return water temp is too high.
  7. BadgerBoilerMN

    BadgerBoilerMN New Member

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    There is condensation if the combustion efficiency is above 96%.

    Not taking away from your success. The modulating output on a residential solid fuel boiler (not gas-condensing) is extraordinary. It also lowers your fuel bill another 5-10%. Now, if it would just condense...hhheheee
  8. Tennman

    Tennman Minister of Fire

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    So pellet boilers don't require storage? Doesn't sound like yours needs it.
  9. heaterman

    heaterman Minister of Fire

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    Tennman.

    In most cases I would say that this particular one does not need storage due to its ability to reduce output to match the load. Can't speak for other brands that fire at a fixed rate and do not have the ability to modulate the burner.
    I think the only instance that I would think about storage using this piece of equipment would be where it was connected to a forced air system using a coil in the plenum of a furnace. IE; an instant on/off system.
    A small 30-40 gallon buffer tank (not really storage ) would allow the boiler to fire up while the furnace pulled heat from the tank. The actual call for heat from the boiler in that case would probably come from the buffer tank. It would simply keep that up to desired temp and the house system could do whatever it wanted.
    When connected to about any kind of a system that has a little mass I would say it's not going to be needed and it absolutely would not be needed when working with a radiator based system or a radiant slab.
  10. heaterman

    heaterman Minister of Fire

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    I agree with what you're saying Badge but when you have a system that generates return water temps around 140* or higher you are going to get very little if any condensation even with a gas fired M/C boiler. That being the case, the efficiency of the boiler will be less than advertised. Viessmann has a pretty good chart showing how the efficiency of condensing boilers changes with return water temp. This is especially true with the brands using the Giannoni heat exchanger which uses only half the total area for condensation. Munchkin, Lochinvar, Peerless and others are set up so the coldest water actually only flows through the back half of the HX.

    Speaking of Viessmann, have you used any of their new version wall hungs that are able to vary both fuel and air flow? I have seen those condense with return temps in the 140-150* range. That particular unit takes the entire process into consideration including combustion air temp and relative humidity.
  11. TCaldwell

    TCaldwell Minister of Fire

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    pretty impressive, where are the rest of the testo numbers, with a relatively high o2 and excess air, must be the flue temp keeping the effiency so high.
  12. heaterman

    heaterman Minister of Fire

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    Exactly Tom. I'll change the display to show flue gas temp and post another picture. Good eye on the excess air also. My chimney drafts like a cyclone and even with the barometric wide open it will still pull more than recommended. Seeing that at this point I'm just testing, I'm not going to change anything with the flue.

    These are a little more typical as far as draft and excess O2 are concerned. The test port is right on the collar at the back of the boiler, not in the flue pipe so you are seeing actual numbers before the flue gas can cool in the single wall going to the chimney.
    Factory recommended draft is between .02 to .04 negative pressure. The wind isn't blowing 20mph like it was in the other photo at the top of the post.

    The burner was ramping up between the shot showing the draft and the one with the combustion numbers. Hence the difference in flue temp. Modulation was at 52% in the combustion numbers picture.

    Notice also that the top picture was taken with the Testo set up to assume 10% MC pellets and the bottom one was using an assumption of 20%. You can see what the moisture level of the fuel does to the flue gas dew point.


    Combustion test 4213 008.JPG Combustion test 4213 001.JPG
  13. BoilerMan

    BoilerMan Minister of Fire

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    Interesting to note it's that much cheaper than NG. I assume you have a Mod/con of some type especially with panel rads. What kind of return temps are you feeding the pellet boiler? Are you pri/sec or direct return? What do you see with the testo with the boiler ramped up in the 90+ modulation range? Someday if I'm unable to burn wood I'll be calling you and getting hooked up with a BioWin! There have been some MeEnergy (OkoFEN) pellet boilers going in around here, I'd like to see a comparison, they seem very impressive and $$,$$$

    TS
  14. heaterman

    heaterman Minister of Fire

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    I was surprised too. My gas boiler is a Viessmann Vitola with a Viessmann burner on it.. non condensing, non modulating.but it will run 86-88% efficiency all day long. It was purchased just before the M/C boilers came out and considered to be the best on the market then. In terms of durability it still is.
    I designed my system for a 20-25* temp drop from supply to return and that's what the pellet boiler see's too.
  15. maple1

    maple1 Minister of Fire

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    Not to take away from your BioWin topic focus, but I'd like to see similar type info/threads on other pellet things like add-on heads. I'd suspect an add-on head would appeal to a great deal of us with boilers who like & want to keep our boilers but may wish to switch to pellets from cord wood as time goes on - or even switch an in-place oil boiler to pellets which should have even more sales potentials. My boiler has a factory pellet head option but I have not seen much real-world info on them.
  16. heaterman

    heaterman Minister of Fire

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    If I had one to play with I would gladly do that. :)
  17. maple1

    maple1 Minister of Fire

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    I'm just kind of surprised we haven't read more about pellet heads from others on here - they would seem to me to have big potential for those with oil boilers who want to get off the oil as easily & cheaply as possible. Yank out the oil burner & stick a pellet head in - whammo you're in business.

    (More or less ==c )

    Sorry for the momentary side track....
  18. goosegunner

    goosegunner Minister of Fire

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    Steve,

    Just curious, is this pellet boiler something you plan on keeping installed or is it some kind of test for your knowledge/ future installs?

    gg
  19. heaterman

    heaterman Minister of Fire

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    I just might wind up keeping this thing around. Going to keep an eye on it to see how it responds as the heat demand decreases here this spring............if it EVER decides to warm up that is! :confused:
    I am pretty impressed with it so far. It'll be interesting to see what the cleaning is like when it hits the 1000 hour cycle. Finally after 900 hours I can see a coating of dust in the chimney.. I'll probably report on that process with some pictures too.

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