Has anyone expierenced a decrease in air flow/intake or exccesive amount of smoke through the chimney? I was in the GARN Barn and I heard a loud groan it subsided to a wheez and then disappeared. The GARN is still working, however I have to use more wood than I did when I started in order to raise the temperature. Any ideas??

 Hmmm......Lot's of questions come to mind. Let's start with a little more info before taking a guess at what is going on.

 

How many years has your Garn been in use and when was the last time the flue tubes were inspected? 

Have you checked the screen in the intake hood?

When you say you are using more wood I guess i would like to know compared to what particular point in time. More than last year, last month, last week?

Did you notice this suddenly from one day to the next?

Was the increase in wood use simutaneous with the noise?

 

Thanks

Stev;

 

This sounds like the problem I described in my post "smell smoke in Garn barn" 12-09-2009. For some odd reason I seem to have incomplete combustion all of a sudden. Much more smoke and can now smell smoke when I walk into the building. The exhaust had almost a sweet smell when the boiler was running but I don't have it now. Been running for 4 seasons and this started overnite. Took the fan out, cleaned the tubes again, checked the intake..everything seems normal. Could we have a common problem?

Hi Steve,The GARN has been in use for about three months. When I started it in December 2009, I used one load of wood to raise the temperature to 180*. I have not checked the flue tubes and I did check the screen on the air intake. About five weeks ago while I had just started the fire, the unit made a noise. I checked around for leaks or emissions and did not find any exterior problems. A few days later, I started to realize that I was using more wood to achieve the 180* temperature. In addition, there was an accumulation of creosote inside the fire chamber and I noticed that the unit would continually smoke instead of the half hour that it did in the beginning. Last week I again heard the groaning noise and after that I started to use twice as much wood than when I first started it up in order to raise the temperature to 180*.

Overall a 40* rise, in temperature, to get it to 180*-190*.  I put my hand on the air collar and I can’t feel air flow, I lit a stick match and put it in front of the air collar and it did not bow it out. However what I don't understand is, why is there a good amount of smoke coming out if I can't feel the air flow in; neither from the collar nor from the air hood. Just wondering where it is getting air.

Using same batch of wood this entire time.

Thanks, George <!--[if !supportEmptyParas]--> <!--[endif]-->

 Here's some things to check.

First thing I would do is pull the combustion blower and check the fan wheel for blockage. If that's OK the next step would be to remove the cleanout covers and look at the flue tubes. If they are OK the next place to check would be to see if ashes have accumulated enough at some point to have fallen down into the air collar through the lower air inlet. You can get a small diameter shop vac hose in the lower air opening to suck out any ashes that may have gotten in there. That being said, in the bottom of the air collar, there is a baffle that diverts a percentage of the air flow up and around the collar to the upper air inlet. That can be a tough spot to reach and ashes will have had to build up excessively in order to allow them into that chamber. Actually, ashes in either would indicate that the firebox needs to be cleaned a little more frequently than it has been. 

We had that happen on a pair of 2000's that are under what could be called severe use, to put it mildly. We wound up having to drill a pair of holes in the front of the air collar, on either side of the baffle and loosen the ashes up with a peice of rod bent up for the occasion. Stirring the hardened ashes up with the rod and then blowing in the hole with compressed air eventually got it cleaned out.  After drilling the holes we tapped them, 1/2" fine thread, and plugged them up with a short bolt and a soft brass washer under the bolt head. 

Both of these units were acting much the same as you describe. Excessive smoke, limited heat output, creosote in the firebox and poor fuel/heat conversion were all evident. I'm guessing that the moan or groan you hear has something to do with restricted air flow as there is nothing metal in the unit that can move to cause any noise such as you describe.  

Hello Steve,

I did as you suggested and everything checked out OK. So I went back to the beginning and looked at the blower again. There was a small amount of creosote build up, however nothing to warrent a solution for my problem. I cleaned up what small amount of build up and when I reached down inside the blower housing, behind the flue temperature thermometer plate, I found a blockage. I was getting a storng smell of smoke from there. At this point I removed the themometer plate and found the tube to partially blocked by a hard mixture of ash, creosote, and condensation.

I removed the restriction and we're back in business. From 120* to 180* in three and a half hours. One wheelbarrow full!

Thanks,  George

 When things get plugged up for whatever reason, that's usually where we find the restriction. right on that bend or in the last flue tube.Flue gas temps are low enough in that area to allow some "gunk" to form if the moisture content in the wood is a little on the high side.   That being said, I have several customer who have never had to clean their Garns despite burning for 3 and 4 seasons. Wood quality and moisture content makes all the difference in the world.  

Hello Steve,  Thanks for repeating how important wood quality (primarily lowest possible moisture content?!) is for a good clean burn and thus clean GARN.  We will be burning discarded pallet wood in a GARN 2000 (plan is to have it up and running for the 2010/2011 heating season), which is in large part kiln-dried. Do you or any forum readers foresee or know of any problems with that?

Hankovitch in SW Wisconsin

I beleive you are going to have alot of puffing with material that is that dry, it is going to try to burn so fast and you will not be able to supply enough combustion air. I have a cabinet shop and burn scraps mixed with regular firewood and if I get to many scraps in there at one time I will get a little puffing. So I can't imagine how much puffing your going to have when burning all that kiln dried pallets. I would plan on mixing it with regular firewood to keep puffing to a minimal.

 I will say a full load of kiln dried small dimension fuel would probably get your attention in an unwanted manner. If a person could bundle that type of stuff so it would burn more like a chunk instead of a full load of kindling you could get away with it. The other solutions would be to use smaller loads more frequently or else mix in some larger and less dry pieces. I would bet that a full load of pallet wood might take your flue temp up in the 500* range. Lot's of wasted heat going out the stack.

Hello Doug and Steve,  You two make some excellent points. Doug, I appreciate your sharing the experience with the mix of kiln-dried scraps and regular firewood. Good idea. Steve, your recommendation to bundle the stuff  ‘so it would burn more like a chunk instead of a full load of kindling’ is well taken. I had already thought about careful stacking of the wood load to decrease surface area, but for those who will not stack as carefully as I hope to do, and for those times when I am too rushed or too lazy  to stack wood carefully I can make up some well-packed bundles for anyone to toss into the GARN. I’ll bet you are correct that using pre-bundled pallet pieces could go a long way to addressing what may otherwise create a lot of puffing. We burn the pallet wood now because we can get a cord for about $10.00 from a facility where they cut apart and rebuild pallets. They combust the pallet wood scraps in their two OWBs (non-gasifiers, but are looking for gasifier units as replacements in the future some time), but generate far too much for their own use alone. We get ‘boxes’ (made by setting a pallet on the ground,  nailing pallet runners vertically, to make an approximately 4x4x4 ‘box’) - into which they toss the non-recyclable wood pieces. Most pieces are nearly full-sized (not kindling size, but nevertheless bone-dry!). They cut the pallets apart, so nails do not stick out, making your bundling idea to make a ‘chunk’ very doable.  We currently heat our 120 y/o, 2,000 sq ft, un-insulated farm house with a smoke-belching Empyre 450 OWB (NOT a gasifier, likely ~35% efficient at best), and burn about 60 ‘boxes’ of wood (nominally 25-30 cords!) to keep the house at 66-67 degrees. When it’s windy and cold we can’t get the house above 65F even with the thermostat set at 75! We are converting our barn into our home, and will bulldoze the farm house once we're in the barn/home. We expect our wood consumption to drop by 65% when we use a GARN 2000 to heat our super-insulated 36’ x 104’ Barn/Home. (We just got the green light from our Building Inspector to proceed with our architectural plan, as submitted - we are very excited about making it over this hurdle!...planning on having this Thanksgiving dinner in the barn/home).Last Fall we applied 3” of closed-cell polyurethane foam + elastomeric paint to the outside of our barn, from 3’ below grade up to the top of the 12” thick, 8’ high concrete walls of the former milking parlor, we also sprayed the same foam 2” thick to the underside of the hay mow floor (ceiling of the milking parlor). We added 14 new windows, 3 new doors, and 2 insulated garage doors. We ‘heated’ the entire 3,750 sq. ft. former milking parlor by allowing the +50F to +55F temp of mother earth to passively diffuse up through the concrete floor of the barn. That is to say, we had NO source of heat other than passive geothermal and a bit of sun coming in through South-facing windows. Coldest it got this winter was -14F outside. Temperature inside the former milking parlor fluctuated from +42F to +33 F from December 1 through March 16. This is quite compelling data confirming the ability of externally applied sprayed polyurethane foam to hold in the heat.  We will use 3” of closed-cell polyurethane foam + elastomeric paint on the OUTside of the entire barn, as our insulation/roofing/siding. We plan to keep the ~5,000 sq ft of living space on 2^nd and 3^rd floors at 70F, the first floor (former milking parlor) 1,000 sq ft garage area at 50F, and the remaining 2,750 sq ft workshop on 1^st floor at 65F. We expect to drop wood use by 65% with the super-insulated space and the gasifying GARN with its 85% efficiency. Time will tell, and I will post our results here and in a Forum at Hearth.com as well….as we generate data next heating season.Ken Oaks at Dectra is the sales rep my wife and I met at an Energy Fair in Custer, WI two years ago. He mentioned that there are GARN owners who burn pallet wood. I hope that they and/or Ken will add their comments/experience to the issue of burning kiln-dried wood in a GARN.Thanks again guys for your useful comments.Hankovitch and Heidi in SW Wisconsin