Combustion Analyzer

wooduser

Minister of Fire
Nov 12, 2018
680
seattle, wa
Yes, wood stove combustion is quite variable, but not randomly or infinitely so.

I read a Dutch study that was analyzing emissions from wood stoves and boilers and retrofitting them with ways to clean up emissions, such as electrostatic precipitators. They used combustion analysis to determine how effective that was.

They broke down wood combustion to four stages, and analyzed particulates at each stage according to the combustion gasses being produced at each stage.

Shucks, UI'm sure most people reading this board could characterize several different stages of wood combustion, from igniting kindling and initial warmup of a cold stove through the dying embers at the end of the combustion cycle.

Not as easy as the combustion in a gas or oil furnace, which just lays therre and begs to be analyzed, but not rocket science either.


After all, testing agencies have been doing it in great detail for decades.

As I understand it, with catalytic stoves you typically have a long period of stable stove operation once the catalyst is burning. That would seem to be a good time to analyse the status of your combustion, for example.

Or perhaps someone is having difficulty getting the stove hot enough to start the catalyst burning. That would be a good time to analyze combustion, too. WHY isn't the stove getting hot? Too much combustion air carrying heat away (High O2,, low stack temperature. excessive draft). Too little air for combustion (low O2, high CO2, low stack temperature inadequate draft) Take combustion gas samples in the parts of the combustion cycle where you are having troubles.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
Shucks man, you were the one who protested that the customer was too far away to be provided service!

<<And when the customer is >100 miles away? Just imagine the cost of the service call for round trip travel time alone.>>


I'm really not interested in picking a fight with you guys y'know. I'm just interested in the operation of my own stove, and why so many other people seem to have a lot of trouble making their new stoves work properly. You guys may be doing a bang up job with EVERY stove user you see, and not be able to affect those facts of life.

Give me a little time to unlimber my digital CO meter. It pegs out at 2000 ppm CO, I'll be interested to see what I find in my stack. during various parts of the wood combustion cycle,. Any predictions?
You say you dont want to pick a fight. Yet you continue to insist that i am not doing my job properly because i am not using an analyzer even though you admittedly have no idea how it would be done.

I agree on forced induction units it could be usefull. But we are talking about natural draft units here. Even the draft measurement is constantly changing because of tons of variables. And there is no way for me to adjust much of anything to fine tune those numbers. It comes down to checking wood moisture. Checking the draft at that point and mentally adjusting for outside temp barometric pressure etc. Checking for negative house pressures. And checking operating temps. The rest is experience. Yes it would be great if i could just hook up some equipment and adjust the fuel air mix to make it right but that simply isnt how it works.
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,577
South Puget Sound, WA
The Dutch study is not new, nor is heavy instrumentation of new designs. The Alliance for Green Heat has been doing this in conjunction with Brookhaven Labs. In the past several years they've run a few competitions and just had their second international challenge in Washington DC. Turning these new ideas into - reliable - and - affordable - solutions is the real challenge.
 
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Ludlow

Minister of Fire
Jun 4, 2018
1,082
PA
Yea they do all sorts of lab analyzing but it is with standardized fuel and in controlled conditions.
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,577
South Puget Sound, WA

wooduser

Minister of Fire
Nov 12, 2018
680
seattle, wa
A modern furnace's burn characteristics are not influenced by atmospheric effects on draft.

I'm not quite sure what you mean by this.
. It comes down to checking wood moisture. Checking the draft at that point and mentally adjusting for outside temp barometric pressure etc. Checking for negative house pressures. And checking operating temps.

If that's the data you need to help people, fine.

If you were in a home with negative pressure that was impairing draft, that would be reflected in a combustion gas analysis, including flue temperature and measuring the draft pressure in the flue. It sounds like what you are saying in your comment above is that you don't need all that information in order to identify a draft issue, and you can go directly to looking for causes of negative pressure.

I see comments like that in answering people's questions ----asking about dryers, range hoods and bathroom ventilators. for example.

It's quite common on gas fireplaces with draft hoods that manufacturer's will specify that the fireplace be tested for combustion gas spillage with all the fans in the house turned on, all the windows and doors closed, to see if the fireplace will operate properly under those conditions. Perhaps that would be a useful test for wood stoves, as well.

Many gas fireplaces have continuous testing for proper draft, by means of a temperature sensitive limit switch that opens and shuts off the burner if spillage from the draft hood occurs.

Wood stoves don;t have that kind of check ----they can continue to operate, sort of, even with impaired draft and venting. Of course that's likely to produce complaints about the stove, even when the stove isn't actually the problem.


As this discussion perhaps illustrates, it's not even actually necessary to do a combustion analysis to begin to understand the issues surrounding wood stove system operations. Certain things are necessary to have good combustion. If one or more are lacking, you can expect to have problems. So as a problem is identified, you can tick off the elements of good combustion which might be causing or contributing to the problem, and check those out as needed.

I wonder if that kind of analysis would help to identify an overfiring condition in a wood stove, my earliest question,. An overfiring condition would likely be characterized by very high stack temperatures, but how high is too high? That's undefined. without guidance from the manufacturer
Excessive draft might be a cause of overfiring, as would improper operation of the stove, such as leaving a bypass open, presumably. (causing the excessive draft.) That would also be reflected in high O2 and low CO2 levels, again reflecting excess combustion air. Improper fuel ----too dry, too finely split or too much, could contribute to that, creating an excess of available fuel to burn. Still, no real way to know how much is too much without guidance from the manufacturer, or good judgement on the part of the stove operator.

Perhaps the reason overfiring can't be determined by combustion analysis is that, strictly speaking, overfiring is not a combustion problem ----it's a question of damaging the stove, Overfiring and damage to a stove can presumably be caused despite having good combustion. Combustion is fine, but too much for safe operation of the stove.

So goes my thinking and analysis.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
I'm not quite sure what you mean by this.



If that's the data you need to help people, fine.

If you were in a home with negative pressure that was impairing draft, that would be reflected in a combustion gas analysis, including flue temperature and measuring the draft pressure in the flue. It sounds like what you are saying in your comment above is that you don't need all that information in order to identify a draft issue, and you can go directly to looking for causes of negative pressure.

I see comments like that in answering people's questions ----asking about dryers, range hoods and bathroom ventilators. for example.

It's quite common on gas fireplaces with draft hoods that manufacturer's will specify that the fireplace be tested for combustion gas spillage with all the fans in the house turned on, all the windows and doors closed, to see if the fireplace will operate properly under those conditions. Perhaps that would be a useful test for wood stoves, as well.

Many gas fireplaces have continuous testing for proper draft, by means of a temperature sensitive limit switch that opens and shuts off the burner if spillage from the draft hood occurs.

Wood stoves don;t have that kind of check ----they can continue to operate, sort of, even with impaired draft and venting. Of course that's likely to produce complaints about the stove, even when the stove isn't actually the problem.


As this discussion perhaps illustrates, it's not even actually necessary to do a combustion analysis to begin to understand the issues surrounding wood stove system operations. Certain things are necessary to have good combustion. If one or more are lacking, you can expect to have problems. So as a problem is identified, you can tick off the elements of good combustion which might be causing or contributing to the problem, and check those out as needed.

I wonder if that kind of analysis would help to identify an overfiring condition in a wood stove, my earliest question,. An overfiring condition would likely be characterized by very high stack temperatures, but how high is too high? That's undefined. without guidance from the manufacturer
Excessive draft might be a cause of overfiring, as would improper operation of the stove, such as leaving a bypass open, presumably. (causing the excessive draft.) That would also be reflected in high O2 and low CO2 levels, again reflecting excess combustion air. Improper fuel ----too dry, too finely split or too much, could contribute to that, creating an excess of available fuel to burn. Still, no real way to know how much is too much without guidance from the manufacturer, or good judgement on the part of the stove operator.

Perhaps the reason overfiring can't be determined by combustion analysis is that, strictly speaking, overfiring is not a combustion problem ----it's a question of damaging the stove, Overfiring and damage to a stove can presumably be caused despite having good combustion. Combustion is fine, but too much for safe operation of the stove.

So goes my thinking and analysis.
Finally!!!! That is what i have been telling you. We dont need to analyze the exhaust it wont help us with natural draft woodstoves in the feild.
 

peakbagger

Minister of Fire
Jul 11, 2008
4,630
Northern NH
In Alaska they are testing the German oekotube on wood stoves now. This was also demonstrated at the Woodheat challenge in DC this month. To date electrostatic precipitators have been to expensive, unreliable, inefficient and requiring regular maintenance so it will be interesting to see what the AK testing results show.
http://fm.kuac.org/post/borough-assembly-oks-testing-promising-woodstove-emissions-control-technology
https://www.oekosolve.ch/
The state of Vermont created an air emissions problem about 15 years ago when they heavily subsidized the installation of wood boiler systems at local schools, they replaced fossil fuels with biomass which sounds good up front but the problem was these are large units that are not baseloaded. They are load following with variable loads and they lacked basic air emissions controls. Later units did have some equipment but I dont think they included a solution for small particulate. They were testing ESPs but I dont think they ever found a viable one. The net result is some areas are reportedly non attainment for small particulate and the school boilers are one of the main causes.
 

wooduser

Minister of Fire
Nov 12, 2018
680
seattle, wa
Finally!!!! That is what i have been telling you. We dont need to analyze the exhaust it wont help us with natural draft woodstoves in the feild.

Heh, heh! O-K!

But I entered here trying to understand how MY stove was working, and how to determine the point at which overfiring might damage my stove.

You guys apparently do you parts of the methods of combustion analysis to solve problems you deal with. And there's no need to go farther than you need to to solve the issues you deal with. It wasn't clear to me what methods you used to do that until you began explaining them.

And it now appears that overfiring isn't something that can be determined by combustion analysis anyway, it's about damage to the stove, not defects in combustion, which is interesting. That's also what you guys were telling me, but I didn't understand that at the time.

Do you guys get guidance from the manufacturer on what the acceptable range of draft through the stove should be? Of course that, too, would vary, perhaps widely, with varying stages of the combustion process.

In the absence of guidance from the manufacturer, it sounds like you have to make a judgement on acceptable draft, for example, based on your own observations of the stage of combustion, and decide if it's too low, too high or acceptable. I'm guessing you'd use the stove operating temperature, flame appearance and such in making that judgement, perhaps measuring the draft if that seemed like it might be helpful. Checking on the operation of fans extracting air from the dwelling and the amount of air infiltration might be a part of that evaluation, especially if a problem is observed.

Am I starting to get an idea of how you do your work?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
Heh, heh! O-K!

But I entered here trying to understand how MY stove was working, and how to determine the point at which overfiring might damage my stove.

You guys apparently do you parts of the methods of combustion analysis to solve problems you deal with. And there's no need to go farther than you need to to solve the issues you deal with. It wasn't clear to me what methods you used to do that until you began explaining them.

And it now appears that overfiring isn't something that can be determined by combustion analysis anyway, it's about damage to the stove, not defects in combustion, which is interesting. That's also what you guys were telling me, but I didn't understand that at the time.

Do you guys get guidance from the manufacturer on what the acceptable range of draft through the stove should be? Of course that, too, would vary, perhaps widely, with varying stages of the combustion process.

In the absence of guidance from the manufacturer, it sounds like you have to make a judgement on acceptable draft, for example, based on your own observations of the stage of combustion, and decide if it's too low, too high or acceptable. I'm guessing you'd use the stove operating temperature, flame appearance and such in making that judgement, perhaps measuring the draft if that seemed like it might be helpful. Checking on the operation of fans extracting air from the dwelling and the amount of air infiltration might be a part of that evaluation, especially if a problem is observed.

Am I starting to get an idea of how you do your work?
Yes most offer a draft range. But it honestly is rare for me to test draft on a woodstove. I can usually tell if it is going to be a problem just by the height and setup of the chimney.
 

velvetfoot

Minister of Fire
Dec 5, 2005
9,973
Sand Lake, NY
I think a problem is that stoves are designed so you can't monkey with them as much. I had a problem with high draft on my insert. I looked at it a lot and finally figured out a way to block air intake and install a control of sorts (a piece of sheet metal wrapped around a magnet) over the remaining intake hole. Now, it runs like it should.
 

saydinli

Burning Hunk
Nov 6, 2016
233
Near Fergus Ontario
I think a problem is that stoves are designed so you can't monkey with them as much. I had a problem with high draft on my insert. I looked at it a lot and finally figured out a way to block air intake and install a control of sorts (a piece of sheet metal wrapped around a magnet) over the remaining intake hole. Now, it runs like it should.
I was talking to Pacific Energy yesterday about controlling draft and he said that the EPA regulations has hand cuffed the manufacturers with the ability to control draft by reducing air intake.
They now have to resort to other methods to control draft which restrict chimney flow like a flue damper or restricter plate.

PE installed a 3.5” restricter plate under my chimney cap last week . Helped some, but I still have a high draft issue. They’re back to the drawing board trying to figure out how to slow down the draft on my FP30 zero clearance so I can burn full loads N/S without it going nuclear.


Sent from my iPhone using Tapatalk
 

velvetfoot

Minister of Fire
Dec 5, 2005
9,973
Sand Lake, NY
They’re back to the drawing board trying to figure out how to slow down the draft on my FP30 zero clearance so I can burn full loads N/S without it going nuclear.
If you look at the design, and think hard, maybe you can figure it out. My stove's air control shutter is encased in steel, but there still was a source of air that could be blocked/controlled. Seek.
 
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saydinli

Burning Hunk
Nov 6, 2016
233
Near Fergus Ontario
If you look at the design, and think hard, maybe you can figure it out. My stove's air control shutter is encased in steel, but there still was a source of air that could be blocked/controlled. Seek.
I know what you are referring to but why would "I"do that? They (Pacific Energy) designed the fireplace, they (dealer) installed it to PE's specs. They have installed the restricter plate and blocked off the OAK. As long as its is warranty, I'm going to let the experts solve the issue. Maybe it'll help others in the end as well. It's they're problem to solve.
If I do something to it and it causes other issue, then it becomes my problem. ;)
 
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wooduser

Minister of Fire
Nov 12, 2018
680
seattle, wa
I think a problem is that stoves are designed so you can't monkey with them as much. I had a problem with high draft on my insert. I looked at it a lot and finally figured out a way to block air intake and install a control of sorts (a piece of sheet metal wrapped around a magnet) over the remaining intake hole. Now, it runs like it should.

So---- did you figure out what was causing the excessive draft?

I've been reading threads, and often our board Xperts can zero in on the cause of problems and offer ideas on how to solve them. And that's fine.

But suppose those ideas don;t work, or it's not clear what the issue might be. If you have an installer who claims the stove is just hunky dory, how do you dispute the claim of an expert? And if you are an expert, what do you do if you are still puzzled about the nature of a problem and can';t decide what it is?

It seems to me that at that point, a combustion analysis that measures the relevant factors of the flue gasses would be worthwhile. That might include measuring the flue gas temperature, oxygen level, CO2, carbon monoxide and draft using instruments. It's apparent that measuring flue gas temperature is often called for in the threads on this board ---- perhaps because it's easy to do compared to other elements of a combustion analysis.

But if you had all the elements of a combustion analysis, you ought to be able to tell with considerable certainty whether there is a combustion problem, and what the nature of that problem is. What you do about it once you know is a different issue. But I suggest that knowing rather than guessing is a step ahead for Xperts, stove dealers and manufacturers ----and customers.

I wonder if stove manufacturers who might shrug off anecdotes about problem stoves might take complaints more seriously if they had such results to bring to engineers. If there is a defect in a stove, they ought to want to know about it. And perhaps the engineers who designed a stove could offer beneficial advice if they are given hard data about the nature of a problem.

As a last resort, a customer with a stove that doesn't work might consider filing a small claims court action and backing up their complaint for damages with the expert who did the combustion analysis and the data from that analysis. If I were a stove dealer or manufacturer, I wouldn't want to be defending my stove against hard data that makes a prime facie case that the stove doesn't meet the terms of the warranty unless I had a very good explanation of why that was wrong.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
So---- did you figure out what was causing the excessive draft?

I've been reading threads, and often our board Xperts can zero in on the cause of problems and offer ideas on how to solve them. And that's fine.

But suppose those ideas don;t work, or it's not clear what the issue might be. If you have an installer who claims the stove is just hunky dory, how do you dispute the claim of an expert? And if you are an expert, what do you do if you are still puzzled about the nature of a problem and can';t decide what it is?

It seems to me that at that point, a combustion analysis that measures the relevant factors of the flue gasses would be worthwhile. That might include measuring the flue gas temperature, oxygen level, CO2, carbon monoxide and draft using instruments. It's apparent that measuring flue gas temperature is often called for in the threads on this board ---- perhaps because it's easy to do compared to other elements of a combustion analysis.

But if you had all the elements of a combustion analysis, you ought to be able to tell with considerable certainty whether there is a combustion problem, and what the nature of that problem is. What you do about it once you know is a different issue. But I suggest that knowing rather than guessing is a step ahead for Xperts, stove dealers and manufacturers ----and customers.

I wonder if stove manufacturers who might shrug off anecdotes about problem stoves might take complaints more seriously if they had such results to bring to engineers. If there is a defect in a stove, they ought to want to know about it. And perhaps the engineers who designed a stove could offer beneficial advice if they are given hard data about the nature of a problem.

As a last resort, a customer with a stove that doesn't work might consider filing a small claims court action and backing up their complaint for damages with the expert who did the combustion analysis and the data from that analysis. If I were a stove dealer or manufacturer, I wouldn't want to be defending my stove against hard data that makes a prime facie case that the stove doesn't meet the terms of the warranty unless I had a very good explanation of why that was wrong.
And what exactly are you basing any of those ideas on?
 

Ludlow

Minister of Fire
Jun 4, 2018
1,082
PA
At what timestamp of the burn would you make the baseline?
 

wooduser

Minister of Fire
Nov 12, 2018
680
seattle, wa
And what exactly are you basing any of those ideas on?
On the science of combustion.

I see that when people have questions about the performance of their stoves, you don't hesitate to ask them their stack temperature. Stack temperature is one element of combustion analysis.

You want to know that data but not to collect further information on the performance of the stove?

If you had a stove that was working poorly and you didn't have a solution to the problem yourself, what information would you like to be able to provide to your boss or an engineer at the company that made the stove by way of soliciting ideas and information on what the problem might be?

Anecdotes would be better than measurements and data?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
On the science of combustion.

I see that when people have questions about the performance of their stoves, you don't hesitate to ask them their stack temperature. Stack temperature is one element of combustion analysis.

You want to know that data but not to collect further information on the performance of the stove?

If you had a stove that was working poorly and you didn't have a solution to the problem yourself, what information would you like to be able to provide to your boss or an engineer at the company that made the stove by way of soliciting ideas and information on what the problem might be?

Anecdotes would be better than measurements and data?
I have already told you exactly what information i need to diagnose problems. Dont you think that if that info was usefull in any way to our feild there would be sweeps doing it? I am on a few professional discussion boards where sweeps and installers from all over the world discuss tech and different techniques and no one does it. That is simply because that info would be of absolutly no help.
 

saydinli

Burning Hunk
Nov 6, 2016
233
Near Fergus Ontario
On the science of combustion.

I see that when people have questions about the performance of their stoves, you don't hesitate to ask them their stack temperature. Stack temperature is one element of combustion analysis.

You want to know that data but not to collect further information on the performance of the stove?

If you had a stove that was working poorly and you didn't have a solution to the problem yourself, what information would you like to be able to provide to your boss or an engineer at the company that made the stove by way of soliciting ideas and information on what the problem might be?

Anecdotes would be better than measurements and data?

I've been in discussions with Pacific Energy R&D recently about the excessive draft on my FP30 and never once has the discussion turned to temperatures anywhere on the unit. In fact when I told them about the temps I'm seeing and asked them what temps I should be looking for, he basically said that temps are only a very general guide to whats happening and that they (PE) do not rely on that data to determine how the unit is burning as there are way too many variables involved specific to each installation. The only gauge reading they seem to have any concern with is the one from the Magnahelic. He said once the draft is dialled in to spec , the unit will burn as designed and expected and to meet the EPA guidelines for clean burn.
Having seen how it's done, I can see how the pros in the field can get a sense of how the unit is burning just by looking at the flames and listening to the stove and what it is doing.
 
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wooduser

Minister of Fire
Nov 12, 2018
680
seattle, wa
Well, I have been inspired to send off an e-mail to Bacharach, maker of combustion analyzers, asking them specifically how they might be valuable to have in diagnosing and correcting wood stove problems. I'll report back what they have to say.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
Well, I have been inspired to send off an e-mail to Bacharach, maker of combustion analyzers, asking them specifically how they might be valuable to have in diagnosing and correcting wood stove problems. I'll report back what they have to say.
You do that because they should actually know what they are talking about. But make sure they know you are talking about natural draft woodstoves not forced induction units.
 

velvetfoot

Minister of Fire
Dec 5, 2005
9,973
Sand Lake, NY
He said once the draft is dialled in to spec
Easier said than done...sometimes?

My little tale of combustion analyzers:
I wanted one for my oil burner. I'm just a home heating hobbyist.
I bought an old used one in good shape, externally, that came in a shiny box and had a little printer in it.
I never knew that the sensors have a limited life, and are not cheap, so I never did anything with it.
I wound up buying a new Fyrite old school kit, with the liquid solutions, and that worked fine, although even the solutions have a set number of uses before they have to be replaced-no time limit though.
These kits come with soot and draft testers as well.

Fancy solid fuel central heaters can use oxygen sensors and variable speed fans to control combustion. A pellet boiler-even the fuel feed is controlled.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,638
central pa
Easier said than done...sometimes?

My little tale of combustion analyzers:
I wanted one for my oil burner. I'm just a home heating hobbyist.
I bought an old used one in good shape, externally, that came in a shiny box and had a little printer in it.
I never knew that the sensors have a limited life, and are not cheap, so I never did anything with it.
I wound up buying a new Fyrite old school kit, with the liquid solutions, and that worked fine, although even the solutions have a set number of uses before they have to be replaced-no time limit though.
These kits come with soot and draft testers as well.

Fancy solid fuel central heaters can use oxygen sensors and variable speed fans to control combustion. A pellet boiler-even the fuel feed is controlled.
Yes with forced induction i absolutly thing an analyzer could be useful.