Starting a fire and running an EPA stove

[St. Coemgen]

There are 3 instruments shown.

1. A Condar probe thermometer on the double-wall stove pipe.
2. The stovetop temperature on a Sandhill thermometer
3. A digital probe readout for the flue using an Auber AT100

IMHO - the only one that matters is the stove top (2). Because that is what is mostly heating your space.

The others simply show temps of flue gas, which can be quite high even at startup (and especially at startup since then the most air is added). But that really mean little. As startup flue gas temps do next to nothing to heating your space with a double walled stove pipe which you seem to have.

So exactly... what was the point of this post?

 

[ABMax24]

IMHO - the only one that matters is the stove top (2). Because that is what is mostly heating your space.

The others simply show temps of flue gas, which can be quite high even at startup (and especially at startup since then the most air is added). But that really mean little. As startup flue gas temps do next to nothing to heating your space with a double walled stove pipe which you seem to have.

So exactly... what was the point of this post?

Flue temp is extremely important in the safe operation of the stove, mainly so the safe operating limits of the stove pipe are not exceeded.

It is also important in the efficient operation of the stove, spiking the flue at say 1200F while heating up the stove may warm it up faster, but also sends over 50% of the heat from the wood straight up the flue.

Flue temp also gives an indication (within reason) of what the stove top temp is, assuming it is understood that the stove top temp lags behind changes in flue temp. Which again goes back to safety, because its easy to have a spike of 1000+F in the flue, and never see that on the stove top.

 

[St. Coemgen]

Flue temp is extremely important in the safe operation of the stove, mainly so the safe operating limits of the stove pipe are not exceeded.

It is also important in the efficient operation of the stove, spiking the flue at say 1200F while heating up the stove may warm it up faster, but also sends over 50% of the heat from the wood straight up the flue.

Flue temp also gives an indication (within reason) of what the stove top temp is, assuming it is understood that the stove top temp lags behind changes in flue temp. Which again goes back to safety, because its easy to have a spike of 1000+F in the flue, and never see that on the stove top.

First, modern stoves and flues are designed to deal with high temps. Extra high temps are mostly only found in a chimney fire, and any modern flue should also be coded to deal with a chimney fire.

Second, none of the temps reported get anywhere near the temps you report "of concern".

And clamming flue temps are a definiton of "efficiency" are dubious. Most efficiency in a modern stove happens in the stove, not in the flue. Catalytic stoves, as just one example. If you have a bot bellied stove from 1880, then you may be correct. But if not....

And even short term high temps are also suppose to be coded into the flue by code. So are also okay, and within safety margins (if the flue was installed to code). That is, flue temps are only needed for the neophyte (and as a backup if you never cleaned your flue and have a chimney fire). After a while, you should "get it", and learn how to deal with your stove properly.

So the flues, if modern, already are coded into spikes in temps, etc.. Even to the extremes you mentioned.

If one is running temps at such extremes constantly, then they are doing something wrong.

And again... These were start up temps. These always get the most blasts of air, and are often a lot hotter then "constant running" temps. So you need to put that into perspective.

Hope this helps.

 

[ABMax24]

First, modern stoves and flues are designed to deal with high temps. Extra high temps are mostly only found in a chimney fire, and any modern flue should also be coded to deal with a chimney fire.

Second, none of the temps reported get anywhere near the temps you report "of concern".

And clamming flue temps are a definiton of "efficiency" are dubious. Most efficiency in a modern stove happens in the stove, not in the flue. Catalytic stoves, as just one example. If you have a bot bellied stove from 1880, then you may be correct. But if not....

And even short term high temps are also suppose to be coded into the flue by code. So are also okay, and within safety margins (if the flue was installed to code). That is, flue temps are only needed for the neophyte (and as a backup if you never cleaned your flue and have a chimney fire). After a while, you should "get it", and learn how to deal with your stove properly.

So the flues, if modern, already are coded into spikes in temps, etc.. Even to the extremes you mentioned.

If one is running temps at such extremes constantly, then they are doing something wrong.

And again... These were start up temps. These always get the most blasts of air, and are often a lot hotter then "constant running" temps. So you need to put that into perspective.

Hope this helps.

All that is fine and dandy if the stove is installed exactly per the recommended setup given by the manufacturer, most are not, there's a difference between meeting code, and the best install practice. My stove can hit 1600F flue temps 10 minutes after lighting, well beyond the 1400F brief forced firing my stove pipe is designed for, and into the 2100F max limit for a chimney fire, this is not caused by a chimney fire either, solely based on flue gas leaving the stove. A temperature that would never be seen on a STT gauge, a device you champion as the best and only device to use.

Sure chimneys are rated to a certain temperature, and yes can be pushed to that temperature, but it also follows that limiting high temperature thermal cycles of these components ensures longer life.

If you don't like flue temps being used for efficiency calculations then please write to the EPA, or CSA, or Intertek, or any other testing agencies that have adopted the stack loss method as the accepted methodology for confirming wood stove efficiency. Yes efficiency is determined by the design of the stove, but heat that escapes the stove and goes up the flue clearly isn't being transferred to the room, ie lost efficiency.

If you choose to run high flue temps on startup go ahead, I and many others choose to run lower flue temps on startup to ensure more of our hard work (in the form of firewood) goes into our homes as heat.

I fail to see the short comings in this how-to article by @begreen that you are pointing out. I think the majority of members on this forum, and stove manufacturers alike, will agree that this article provides safe and proven guidance on the operation of a wood stove.

 

[begreen]

The point of the posting is education. It is specific to startups (that's in the title). Not everyone is familiar with stove burning. Many have no reference to what is normal. Yes, modern flue systems can take high temp, but sustained, repeated runs at high temp will degrade the system quicker and solely using the stovetop temperature can lead to a major increase in emissions and inefficiency due to wasted fuel. Keeping flue temps within reason reduces fuel waste, meaning more heat reserved for the house and a longer burn time. Stovetop temperature is a lagging indicator. There's no point in wasting fuel.

This website has a wealth of good information. The third video on this page of efficient wood burning also shows top-down lighting.

A non-commercial service in support of responsible home heating with wood - Wood Heat Videos

The Wood Heat Organization was formed to support the public in the responsible use of wood energy in the home. We fulfill our mandate by providing reliable information, by conducting research into wood heating-related issues and by representing the public interest in discussions of policies that...

woodheat.org

 

[clancey]

Just a wonderful thread and I am reading the whole thing "little by little"...I am assuming most wood stove burners like the NS burn because of being able to put more wood in the box in the winter time...Does everyone who lights a fire have to keep the door to the stove ajar?. I am going to get just the temperature gauge that you put on the piping --is this adequate? Great information here and I am getting my feet wet here to learn about "wood burning"..thanks clancey

 

[begreen]

A probe thermometer in the double-wall stove pipe will be very helpful. It should be placed about 18-21" above the stovetop. You may also want a stovetop thermometer as a guide for cooking temperature, but for efficient burning, it is less helpful than the flue thermometer.

 

[clancey]

Thanks how about the EW loading or the NS loading why the difference--? I am thinking that the NS loading with the end of the logs facing you would be more popular because one could load more logs into it...? When you light a stove do you have to keep the door open a bit in the beginning--these questions are important for me to know? I need to contemplate fully on this--lol getting geared up so to speak..lol clancey

 

[bholler]

Thanks how about the EW loading or the NS loading why the difference--? I am thinking that the NS loading with the end of the logs facing you would be more popular because one could load more logs into it...? When you light a stove do you have to keep the door open a bit in the beginning--these questions are important for me to know? I need to contemplate fully on this--lol getting geared up so to speak..lol clancey

Ew vs ns is a combination of personal preference and stove design. Either works but I prefer ns. As far as leaving the door cracked that is determined by the stove chimney wood outside temp house pressure and many other variables. There is no way to know if you will need to or not untill you try it.

 

[begreen]

Yes, N/S is my preference. One can put more wood in the stove without concerns of logs rolling into the glass.

 

[NickW]

Just a wonderful thread and I am reading the whole thing "little by little"...I am assuming most wood stove burners like the NS burn because of being able to put more wood in the box in the winter time...Does everyone who lights a fire have to keep the door to the stove ajar?. I am going to get just the temperature gauge that you put on the piping --is this adequate? Great information here and I am getting my feet wet here to learn about "wood burning"..thanks clancey

I only need to keep the door open a crack on cold starts or low coals when I lose my draft. Hot reloads the bottom logs are lit before I'm done reloading and it still has draft with the door closed and air open. Cold starts for me are door fully open 5-10 minutes, 1" for 5 minutes, 1/4" for 5 minutes (or so...). As @bholler said, there are a lot of variables.

 

[bigealta]

I only need to keep the door open a crack on cold starts or low coals when I lose my draft. Hot reloads the bottom logs are lit before I'm done reloading and it still has draft with the door closed and air open. Cold starts for me are door fully open 5-10 minutes, 1" for 5 minutes, 1/4" for 5 minutes (or so...). As @bholler said, there are a lot of variables.s

You should try Top Down on Cold Starts. With old style bottom up i used to also need to crack the door for a while. With top down, The door gets closed immediately and the secondary flames start firing within 3-4 minutes.

 

[Split]

This is good info in here. Thanks. So it's generally OK on starts to have flue Temps go up to around 1200? Mine spikes then heads down to stay at 900-1000 for a while then goes down slowly. I'm thinking this year, now that I have properly seasoned wood that I might be able to shut down the air intakes sooner so I don't get such high spikes. Also I'm hoping by shutting it down a bit earlier I'm able to put more energy into heating the stove/room.

 

[NickW]

This is good info in here. Thanks. So it's generally OK on starts to have flue Temps go up to around 1200? Mine spikes then heads down to stay at 900-1000 for a while then goes down slowly. I'm thinking this year, now that I have properly seasoned wood that I might be able to shut down the air intakes sooner so I don't get such high spikes. Also I'm hoping by shutting it down a bit earlier I'm able to put more energy into heating the stove/room.

I set the alarm on my flue probe at 900 and try to not set it off. I believe it is best to stay under 1000F to prolong the life of the flue.

Yes, the whole burning experience is soooo much better with properly seasoned wood. My first year with "OK, but not great" wood was better than the old smoke dragon. The second season was drastically improved in all ways from the first from start up to length of time for effective heat to coaling.

 

[jfhull71]

Questions about starting a fire and avoiding a runaway stove come up so frequently I decided to document starting our stove. This is a Pacific Energy Alderlea T6 with about a 3 cu ft firebox. The stove is connected to a straight-up, 20' interior flue. The outside ambient temperature is 34ºF. The blower was off all the time for these shots. The firewood is douglas fir at about 17% moisture content. This is a N/S loading. An E/W loading start will follow.

NOTE: as testing will show, the older Condar flue thermometer is reading low. It's due for replacement.

There are 3 instruments shown.

1. A Condar probe thermometer on the double-wall stove pipe.
2. The stovetop temperature on a Sandhill thermometer
3. A digital probe readout for the flue using an Auber AT100

View attachment 255400
Here is the stove loaded with a gap in the middle for a top-down start. 3 balls of newspaper and a few flakes of kindling on top.

View attachment 255401
Fire started, flue temp and stove top temp is <100ºF. Door left open about 1/2".

View attachment 255402
Time to insert a split into the gap then close the door, with the air control wide open. This picture is showing the stove, the Condar, the stove top, and the Auber.

View attachment 255403
Dry doug fir takes off quickly. This is about 5 minutes later, time to reduce the air to 50%. There will be no creosote worry here even though the stove top temperature is low.

View attachment 255404
Just a few minutes later and secondary burn is getting robust. Reduce air to about 70% closed. Note how stove top temp is still low and the probe flue thermometer is lagging far behind the digital probe. The digital probe reacts almost instantly.

View attachment 255405
After 5 minutes the fire is going strong, close down air almost all the way, maybe 85%. If it was 10º colder outside I would be closing the air all the way due to increased draft. Note the stove top temp. This is why it is not helpful in a cold start. It takes time to heat up the mass of the stove, while the flue temp is already very high. Unfortunately, the Condar flue probe is sluggish which is less helpful, but combined with the visual cue from the firebox it's obvious that the air needs to be closed down until the flames slow down.

View attachment 255406
Just a few minutes later the fire settles down. Secondary combustion is now robust. No need to change anything. Stove top temp still coming up.

View attachment 255407
The stove has been cruising for 20 minutes and is almost up to temperature. The stove top settled at 625º. The analog probe thermometer is finally catching up to the digital probe.

Note that this is just one example of a N/S load of softwood in a large stove. There are many variations. This load of wood has a lot of young growth and sapwood in it so it is not as dense as old growth doug fir and it burns quicker with less heat. Every fire will have a somewhat unique character depending on firebox size, how much fuel is loaded, how tightly it is packed, outside temperature, and mostly, the operator. If you don't have thermometers, consider one, at least for the flue temp. And use your eyes for visual cues about the stage of the burn.
Hope that helps.

Don't know how you could runaway an EPA stove (without gasoline and the door open) with the combustion air as restricted as it is

 

[NickW]

You can absolutely have a runaway with an EPA stove. I guarantee I could melt my NC30 where it sits if I tried. I could probably overfire the Stratford II also, but it would take a while...

 

[ericm979]

I can get my EPA Flame Energy stove to run away too.

I think that for the recirculating type EPA stoves, the limitation is on how low you can adjust the air. The air tubes need a certain amount of air to burn the smoke. If they let you cut off the air too far, reburn would stop and the stove would smoke.

My understanding is that this is less of a limitation on a catalyst type EPA stove.

 

[begreen]

Don't know how you could runaway an EPA stove (without gasoline and the door open) with the combustion air as restricted as it is

With decent draft and dry wood it's pretty easy to do. There's plenty of air for a roaring fire. Turning it down in a timely fashion is key to avoiding overfire and wasting a lot of heat up the flue.

 

[bigealta]

Don't know how you could runaway an EPA stove (without gasoline and the door open) with the combustion air as restricted as it is

Ash pan door left open or even cracked will run away faster than usane bolt.

 

[begreen]

Ash pan door left open or even cracked will run away faster than usane bolt.

DDT (Don't do that)

 

[jfhull71]

Drolet 1800 coals heavily and my flue is 13'3" from stove top... Installation manual"recommended" a 1'extender on all installations.... I'm thinking a 18" or 24" may be better for my installation...seeing Eddy current drafting over the roof on hot reloads that smoke for 5 minutes.... problem is I can't find any of these on the Drolet website.... I have found other brands but nothing from SBI, I need to make sure it's compatible with my SBI liner and rain cap before ordering....any suggestions from the group?
Stove never smokes the house, but once secondaries die all I end up with is half a stove of coals... even with air control wide open.

 

[begreen]

When you say SBI liner, was this purchased from the Drolet website?

Heavy coaling can also be a symptom of wood that has more moisture in its core and is not fully seasoned. It takes longer to burn down. Open up the air 50% and put a couple 2" splits on top to help provide heat while burning down the coals.

 

[jfhull71]

No purchased through a US site.... but liner and all components had SBI decals. And it's not moisture....wood across species is all 20% or lower and I don't have time for splits to burn down coals....I work for a living and need to load and go 5 days a week

 

[begreen]

No purchased through a US site.... but liner and all components had SBI decals. And it's not moisture....wood across species is all 20% or lower and I don't have time for splits to burn down coals....I work for a living and need to load and go 5 days a week

This is 6" stainless chimney liner on a Drolet 1800 insert, correct? If so, this should work.
(broken link removed to https://www.chimneylinerkit.com/Chimney-Flue-Extender-p/chimney-flue-extender.htm)

 

[jfhull71]

This is 6" stainless chimney liner on a Drolet 1800 insert, correct? If so, this should work.
(broken link removed to https://www.chimneylinerkit.com/Chimney-Flue-Extender-p/chimney-flue-extender.htm)

Correct and thank you, just Wanted to get the right part that works with my liner system, thanks for the link