Bridging and blowouts? What has changed?

[MarkW]

I'm running my Biomass 60 with the settings in the tuning sticky and have been for 2 months now. With no changes made, I'm in unable to burn through a load.
I can't even burn through 4 or 5 pieces set directly on the nozzle. Same wood,split size seems iirrelevant. When running, stack temp seems to be at 275 just as before.
I'm at a loss. Played with fan speed to no avail. Changes in the shutter setting. Nothing seems to keep it going. I'm at a loss and tomorrow's weather is not going to be good for a boiler that won't fire.

 

[Fred61]

I've experienced the exact same situation with my Eko. Screwed up all my settings that had been ideal for some time. Although you say the wood is the same it's obvious that wood is the one thing that's not a constant here. Could the wood have been taken from a different row?. Perhaps one that didn't get as much airflow of sunlight or perhaps further down on the row. Do you have a moisture meter? When was the wood cut, split and stacked? What species are you burning?

 

[MarkW]

I'm 3 rows in this season with no issues until now. It's mixed species but primarily maple and oak. I did just get into a bit of tulip and this is when my troubles first began. I know tulip burns poorly in a regular furnace so I quickly discarded the tulip and returned to the other species. The problem remained.
My wood is seasoned 2 years since cut/split. I wondered if maybe it was because it's the middle of the pile so I got some off the other end. No improvement.
Yesterday, we bought 2 more cords because we aren't going to make it through winter with what we have on hand. 2 years on this stuff, too. Mostly oak and maple. Same issue.
It burns great as long as it's on the nozzle.
I suspect the wood, too. Just not sure what to do about it now.

 

[Fred61]

Well, I still think it's the wood. Oak needs three years of drying in order to burn well in a gasser so take that out of the pipeline for starters. The last "seasoned" wood I bought was sitting two years in log form and then bucked up to my length specifications. That was "wet" wood. If you found a firewood vendor that actually knows what dry wood is, he's 1 in a million. You need to check the moisture content. Do you have any cabinet shops or furniture makers near you that may have a moisture meter you could borrow? The piece needs to be split and the new exposed surface is where you check the moisture.

It's a classic wood problem in these gassers. With higher moisture wood, the coal bed burns out from under the log faster than the log produces enough more coals to sustain the fire. Try some pallet wood if you can scrounge some up or perhaps try some biobricks.

 

[maple1]

How big are your splits? Have you tried replitting quite small? I have an electric splitter in my basement that gets used quite a bit at times, although not a lot so far this winter. No doubt a wood issue, but I have been able to improve when I needed to by resplitting. Won't get it up to ideal again, but should improve it. If you can resplit a whole bunch, it will dry more in a few days while waiting to be fed to the boiler, if you can get some warmth & air cirulation over it. A box fan on low helps with that.

 

[mr.fixit]

I would try smaller splits also,and if there is alot of ash built up in front of and behind the nozzle it can hold up longer pieces of wood.

 

[woodsmaster]

What part of ohio are you from. Im in the nortwest corner. your welcome to come take a look at mine, but I'd guess it's probably the wood

 

[MarkW]

Opposite side of the state woodmaster, but thanks for the offer.

So I went and had some splits checked at the local supplier whereI get stuff to build cabinets and I'm more confused than before.
Readings from 12%-25% with the tulip coming in at the low end and the oak at the high side, as expected. MC doesn't vary much based on where in the stack I pulled it from. The center was a couple % higher but thats it.

 

[MarkW]

maple- smaller splits are doing the same as larger. I considered resplitting to dry sooner until I just got those MC readings.

mr fixit- I have noticed the ash buildup from time to time but I try to keep that from happening. Incidentally, blowby seems to happen most frequently at the door end of the load, ash or no ash buildup.

 

[Fred61]

So you did split the wood before taking the reading, right?

 

[MarkW]

yep

 

[Fred61]

maple- smaller splits are doing the same as larger. I considered resplitting to dry sooner until I just got those MC readings

Smaller splits will also give you more surface area which should help. Can you slow down your fan?

 

[MarkW]

Ive tried the fan speeds from 50-100%. Despite the changes, it seems to run about the same length of time before bridging.

As I noted, the smaller splits didnt improve matters. You'd think it would, right?

I've even tried what someone suggested in another thread of stacking the load against one side so it would be able to slide down the wall. This didn't change anything either. Maybe gravity quit working in my boiler room.

 

[Fred61]

Perhaps it's time to get some bio bricks or pallets. If they burn it's the wood. If they don't I'm stumped!

 

[goosegunner]

Try initially loading 20lbs of small wood to get the boiler going for 20-30 minutes then load more.

gg

 

[rkusek]

What temp does your circ lauch at? And when does if shut off. Many of my early gasser issues disappeared when I set the launch to 165 rather than the default value. Also, is your wood maxed out lengthwise? I cut a few inches shorter now and although I still get a few long pieces by accident I always put them at the top of a load never on the bottom. One more thing are the 2 timeout settings on the controller set for the max times?

 

[rkusek]

Goosegunner makes a good point too. On a cold start or one with little or no coals I prefer to build a fire with 3-4 very small of my driest splits and let it run 10" with bypass open and lower door wide open. Not only does this warm the chimney and provide a red hot bed for instant gassing after loading, when I close the lower door then open the upper 1 second later the fire directs itself downward thru the nozzle allowing for a smokefree loading.

 

[MarkW]

Try initially loading 20lbs of small wood to get the boiler going for 20-30 minutes then load more.

Even when I do get a good bed going, once I load and start a normal run it will just blow out the coals.

What temp does your circ lauch at? And when does if shut off. Many of my early gasser issues disappeared when I set the launch to 165 rather than the default value. Also, is your wood maxed out lengthwise? I cut a few inches shorter now and although I still get a few long pieces by accident I always put them at the top of a load never on the bottom. One more thing are the 2 timeout settings on the controller set for the max times?

Launch is 170 w/set temp at 175. I did reset my controller times from factory. My lengths range from 18-20". It's been doing fine with these lengths since I started running it. I did note that anything near max does tend to be troublesome but I don't have much of that because my splitter won't go over 22".

Perhaps it's time to get some bio bricks or pallets. If they burn it's the wood. If they don't I'm stumped!

I figured I'd try just that tonight to see.

Certainly appreciate all the comments/assistance from you guys. For sport, I pulled the top cover off the turbulator tubes last night just to see if anything was amiss in there. A little fly ash on top of the tubes but nothing else, i.e. cresote, buildup on tubes, etc.

 

[goodwood]

try cleaning out the holes on inside bottom of nozzle, there is 4 or 5 on each side, mine got plugged up with ash a few times

 

[MarkW]

The secondary air in the nozzle opening?

 

[rkusek]

Your lengths, settings, and turbs don't seem to be the problem. 175 for the set temp seems too low especially if your circ launches at 170 but I doubt that is your problem. Check those secondaries and check for ash buildup in the horizontal stovepipe coming out the back of the boiler. You might try just a couple 2x4 short cutoffs at the bottom of your load and turn that set temp to 180-185.

 

[MarkW]

I'll give that a shot, too rkusek. I've been running my set temps lower because of inefficiencies in my current temporary setup. I've been trying to keep differential losses down by running a slightly lower temp. I'll run it up and see what happens, though.

 

[Tennman]

You're getting lots of good advice here Mark. As Rk mentioned, I'm very careful now to prevent an ash buildup in the back and inside the door and rake ashes toward the center so new wood isn't supported at the ends. I'm currently running with my setpoint at 191F and pump on... I think 160F. My storage is not on line yet so it's not unusual for me to check our boiler and see it idling at 196-197F. You should have an advantage of less if no idling. I was also running a lower setpoint temp and experienced far fewer problems when the 60 is running hot and hard. That's what convinced me I needed storage. I doubt blockage is a problem, but when these mysteries arise I start checking things so I know what's NOT the problem. Since you checked the top chamber, I'd also remove the access cleanout on the lower bottom right side. I've had instances where ours wasn't producing heat and found a surprising build up of ash choking flow out of the secondary chamber and covering heat transfer ribs in the back bottom chamber. I doubt that is causing the bridging, but when it's not working normally start eliminating possibilities. As everyone has said, it still smells like wood. I've found the hotter I run my 60 the happier it is and that's particularly true when I have lower quality wood. I have access to a lot of pallets and cut them up and mix them with my splits. I've found burning pallet wood only is too hot and fast because the wood is relatively thin. Lots of good help here and rest assured you'll get it sorted out.

 

[ElkRiverFJ]

I have a BioMass 25 and this is my first season running it. I have almost the exact same issues you seem to have, but I had chalked it up to wood not properly seasoned. My burn schedule is such that I burn a fire for a few hours in the evening to top off storage and it is done before I go to bed so I am just in the habit of poking the fire around every hour or so. I've gotten some of the eco-bricks and mixed them in with some lumber scraps and it does seem to make a difference. I was just trying to get through this season and hope for better results next year. I think I can go 2 days on storage if I could burn a fire overnight, but right now I couldn't keep a fire overnight if I didn't tend to it every hour.

 

[MarkW]

I doubt blockage is a problem, but when these mysteries arise I start checking things so I know what's NOT the problem. Since you checked the top chamber, I'd also remove the access cleanout on the lower bottom right side.

That was one of my first places to check. Though I have no trouble at all making heat when the wood stays on the nozzle, I figured I'd give it a look see. There was a little piled up at each end where the horizontal side paths dump out but not enough to block anything. I vacuumed it out, none the less.

Despite the MC readings, I suspect the wood as well. Though I can't help but wonder why the opposite end of the pile wouldn't burn as well as the end with which I started the season. I guess I'll find out tonight when I get home with some pallet pieces and scrap 2x4's.