how to judge when to kick on the fan during light off?

[pybyr]

Hello all-

It's becoming apparent to me that my remaining wood is, on whole, not as dry as I'd hoped... but it's what I've got ... and I am committed to buying no more oil. Lots of it is White Ash, which is reputed to be pretty decent to burn even when not all that well seasoned, and red pine, which is supposedly in the same category... but anyway, it is harder to get lit than the stuff I was using at the start of using my Econoburn 150.

Given that, I am finding that unless I get a fire going to the optimum point before I shut the updraft flap and kick on the downdraft fan, well... the whole thing kind of goes nowhere, unless I back up, kill the blower, open the updraft flap, get it raging again, then try again- which not only delays heat, but takes up a bunch of time with the fiddling around factor..

This is all with the NoFo "4 minutes to gasification" method- which seemed to indeed produce great light-offs with my original batch of maple and cherry cut during late April 08- it's just that now I am into other wood that really did not get processed until rather late in the season.

Anyone have any suggestions as to how to know/ judge whether and when there is enough of an "updraft burn" going to have confidence that it's time to switch to downdraft mode?

I have a stack thermometer, and a draft gauge (which holds mostly steady thanks to my barometric damper) and also watch the control readout on my Econoburn, but have yet to find the right objective/ intuitive way, at least with my not-so-dry wood, to know when to 'hit the afterburners' by turning on the fan and closing the damper for downdraft

Also, while I am at it, let me ask this, too- my Econoburn 150 does not have a continuously-variable fan, but, rather, has three modes: no fan, slow fan, and high fan. By changing the aimed-for temperature on the PLC controller, I can control whether the fan is in slow or high mode during the initial change from up-draft to down-draft. Any thoughts whether a mild wind or a wild wind is the best way to initiate and build momentum of gasification?

Thanks, as always, for all the knowledge around here and the willingness to share it

 

[Nofossil]

I'd suggest picking up a few pallets - they're generally free and made of kiln-dried hardwood. Doesn't get much better for starting fires. Despite all my technology, I use a magnetic stick-on flue thermometer to tell me when it's ready to kick over.

Your comments about starting a fire with less than perfect wood are right on target. IMHO, gasifiers are not particularly finicky except in those first few minutes. Then, you want the very best wood that you can get.

 

[pybyr]

I'd suggest picking up a few pallets - they're generally free and made of kiln-dried hardwood. Doesn't get much better for starting fires. Despite all my technology, I use a magnetic stick-on flue thermometer to tell me when it's ready to kick over.

Your comments about starting a fire with less than perfect wood are right on target. IMHO, gasifiers are not particularly finicky except in those first few minutes. Then, you want the very best wood that you can get.

Thanks NoFo- what do you consider to be the "right" flue temp? for turning on the fan? I have a thermometer with the probe right in the stack, so I may use a different reading to adjust for the difference, but wondering what you use?

 

[Nofossil]

Thanks NoFo- what do you consider to be the "right" flue temp? for turning on the fan? I have a thermometer with the probe right in the stack, so I may use a different reading to adjust for the difference, but wondering what you use?

External flue temp:

250 - not likely. Feeling lucky?
275 - pretty good odds, especially with dry wood
300 - near certain

Probably corresponds roughly with 450 - 550 degrees internal center-of-stream temps.

YMMV.

 

[Tarmsolo60]

.

 

[pybyr]

NoFo- does your Eko 25 have a multi or variable speed fan? and/ or do you have any other insights as to whether mild wind or a wild wind is the best way to go in the early stages of gasification?

Thanks

 

[Eric Johnson]

With the variable speed blower on the newer EKOs, I think it's best to start off with a relatively high speed (80-100%) until you get good gasifiation, then throttle it back to 50-70% for a longer, more even burn.

Good gasification depends on hot refractory. If you're starting cold, having some volatiles in the mix (yellow birch bark, pine cones, dry pine kindling) helps get gasification going, and hopefully it will heat the refractory up sufficiently in the process. However, if you're dealing with less-than-optimum wood, I would suggest trying to keep hot coals in your boiler as much as possible. That might mean building smaller fires and loading fuel more often, or whatever. The point is that you can get gasification going immediately, even with crappy wood, if you lay it on top of a nice bed of hot coals.

If that's not realistic, then you can put some commercial charcoal around the nozzles on startoff to get something resembling hot coals in fairly short order.

And finally, I found that my boiler operating skills have improved vastly in a season and a half of experience. I don't know exactly why, but it's true.

 

[Nofossil]

NoFo- does your Eko 25 have a multi or variable speed fan? and/ or do you have any other insights as to whether mild wind or a wild wind is the best way to go in the early stages of gasification?

Thanks

All of them are variable speed as far as I know, but my controller is the old one so I have no direct control over fan speed.

My sense (and this is mostly speculation and hearsay) is that you want a very slow speed when you first kick it over, ramping to full throttle over the next couple of minutes. Too much too soon and you blow out the flame. However, you really want maximum burn as quickly as possible to get your refractory temps up.

Here's a picture of my fire starting last night. Chronology:


5:31ish - light fire. Bypass and lower door open, upper door cracked a bit.

5:33 - controller detects rise in stack temp. Asserts control of EKO circulator and starts it at medium speed (wood circ A high). Opens recirc zone valve that allows water to circulate from outlet directly to inlet. Leaves tank circulator on to flush cold water out of EKO. EKO inlet temp begins to rise immediately.

5:34 - Operator foolishly closes bypass and both doors, turns on EKO controller. Secondary combustion does NOT happen.

5:35 - Operator opens bypass damper and lower door for less than a minute, then tries again. Success - secondary combustion established. Combustion temp climbs rapidly to 1100F.

5:47 - controller determines that storage is now ineffective at flushing any additional cold water out of the EKO. Storage circulator turned off. EKO circulator drops to slow speed (wood circ B is high).

5:57 - Inlet temperature protection target reached. Recirc zone valve closed.

5:58 - EKO circ speed increased to medium (wood circ B is high)

6:02 EKO circ speed increased to full (neither wood circ a or b is high, but control is asserted)

 

[pybyr]

you can put some commercial charcoal around the nozzles on startoff to get something resembling hot coals in fairly short order.

And finally, I found that my boiler operating skills have improved vastly in a season and a half of experience. I don't know exactly why, but it's true.

Thanks Eric- you mean the briquettes like people use in barbecue grills?

And I am sure that my skills will improve- I am just bummed at the difference I see between the maple and cherry that I first began running my Econoburn with, which had been cut in late spring 08, and the mix of other stuff that was cut late summer and then not really split and stacked until embarassingly late in the season- the rest of life threw some curve balls that pushed the wood aside. Now I know that, more than my old wood hot air furnace, my Econoburn deserves and appreciates good wood!

 

[Eric Johnson]

It does make a huge difference. Everything is so much easier and more successful when you have really dry wood. Wood cut in the late summer--even if split and stacked right away--is not going work very well.

Yes, I'm talking about charcoal briquettes. That gets expensive. If you have unburned coals left in your firebox, they do pretty much the same thing. Just make sure that they're around the nozzle.

Another thing that people seem to neglect--since it's easy to do--is keeping the nozzle clear. I always take the scraper tool and rake over the top of my nozzles before starting a new fire--or adding wood to a bed od coals--to make sure that they're open. A clogged nozzle is not going to gasify no matter what you're burning.

Nofo might be right about a strong fan blowing out the gasification process on startup. Since I'm generally starting with a bed of coals, I find I get up to temp faster with a faster blower on startup. A cool nozzle may require a bit more care. Once you've got it going good, throttling it back really extends your burntime and probably your wood supply as well.

 

[pybyr]

I'm always careful to clean the ash out of the bottom of the firebox/ surface of the refractory/ opening of the nozzle before starting a new fire. I usually seem to have negligible amount of coals, burning or unburning, when starting a new fire after the old one has gone out some time ago. So far, I am doing periodic full bore burns, usually in the evenings- and actually letting the substantial thermal mass of my house (it's timber and plaster construction) be my de-facto storage- that, plus the fair amount of passive solar gain I get on sunny days makes it tolerable (at least for a single guy who's willing to put on layers) 'til I get the next fire going the next evening. But it does make me want to get successful at getting fires going fast and successfully!

regarding the charcoal briquettes- how do you arrange them in relation to the nozzle? in little rows next to it, or what? I assume that you don't want the briquettes over & across the opening?

Thanks

 

[pybyr]

NoFo- does your Eko 25 have a multi or variable speed fan? and/ or do you have any other insights as to whether mild wind or a wild wind is the best way to go in the early stages of gasification?

Thanks

Here's a picture of my fire starting last night. Chronology:

<snip>

5:34 - Operator foolishly closes bypass and both doors, turns on EKO controller. Secondary combustion does NOT happen.

5:35 - Operator opens bypass damper and lower door for less than a minute, then tries again. Success - secondary combustion established.

It's very encouraging to realize that even the formidable and experienced NoFo occasionally has situations of hang-fire on achieving initial gasification !

 

[leaddog]

Some woods don't coal easily or well and as they burn just turn to ash. If you have some good hardwood put that on the bottem. I had an OWB for many years and once in a while I try and revert to the old ways and don't get into gasification. I tried to add cardboard, old oil, and many other things but if the coals are gone it don't matter if the fire box is full of flaming fire as soon as you try and gointo gasification it goes out. I end up with stiring the wood and trying to shake off as many coals as posible and trying again. Charcoal will help but just remember you need to build that first fire with something that will make coals cause there MUST be coals over the nozzel. Thats why you loose gasification when the wood bridges, the coals burn away and you just pass the gas out the stack.
If I have coals I can just rake the coals and throw some small pieces in and fill up the top and start it up. The stack temp can be down to 100* but as soon as the gas goes thru the coals it gasifies and with in a short time the stack temp is up to 300*
leaddog