Starting a fire and running an EPA stove

[begreen]

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 needs recalibration.

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

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.


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


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.


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 still low.


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.


After another 5 minutes the fire is going strong, tme to close down air almost all the way, maybe 85% closed. If it was 10º colder outside I would be closing the air all the way due to increased draft. Note the stove top temperature. It's catching up but not fully warmed up yet. This is why stove top temp is not as 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.


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


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.

 

[weatherguy]

Have to say I was resistant to the top down fire because I've always did it the old way, after trying it once I'm hooked, I will always do top down. Thanks BG, good thread.

 

[begreen]

Woodcutter Tom said:
I thoroughly enjoyed reading your Starting Fire documentation. Very informative.

I had a couple of questions I wanted to ask. I did not want to mess up your thread so I decided to ask you this way.

1. I am a bit confused about the definition of Flue and Stove pipe. I thought they were basically the same. You have your Auber reading the flue temperature and a probe reading your stove pipe. Could you please explain the different locations. Maybe a picture where each is located would help.

2. In your second set of pictures the Auber displays 190 degrees. To me the flame looks so small as you just started the fire. Do you get that much heat with so little flame? I am trying to factor in your 3.0 cubic foot firebox, but still the flame looks small. Even in the next set of pictures where the Auber displays 298, the flame looks small.

3. When your fire settled in at 625, how long does it stay in that area before it starts to drop? Is the drop fairly rapid, or is it a gradual decent?

4. When you have the door open 1/2 inch, do you get a blowtorch effect? By that I mean does the air seem to rush into the firebox and fan the flames excessively.

Once again, great information. I appreciated it and I am sure many other new stove owners will also.

Tom, these are great questions. I wouldn't mind them showing up in the posting at all. I am going to copy this over to the posting so that others can benefit.

When I say flue, I mean the entire flue system from stove to the chimney cap. Stovepipe strictly refers to the in-the-room pipe that connects the stove to the chimney system. The Condar probe is about 21" above the stovetop, the Auber probe is at about 23" above the stovetop.

In a big firebox, the flame does look small, but remember, this firebox is deep so what you don't see is the flame behind. What looks like a 3" x 4" flame is actually also 12-16" deep. Yes, a few balls of newspaper and a little kindling will take the Auber up a couple of hundred degrees pretty quickly. It's quite sensitive. When you think about it, the heat has nowhere else to go but up the flue.

How long the stovetop stays at peak temp depends on the wood. In this case there was some sapwood that burned pretty quickly. It stayed at around 625º for about 30 minutes and then very gradually declined. The fire was reloaded about 8 hrs later with a stovetop temp of around 275º. At 625º there are flames and those will remain, mostly at the top of the wood as secondaries for at least an hour, sometimes longer. It depends on the wood. The flames become wispier as the fire approaches the coaling stage. After all the volatiles have burned off the flames end, but the coals are still glowing and burn down over the remaining few hours.

If the door is open an inch I get the blowtorch effect. This is helpful at times, but most of the time I leave the door open just a tiny bit. Maybe 1/8 to 1/4". If the door is open too much it tends to fan the fire too much to the rear of the stove and can actually snuff out flames in the front.

When I get time I will do this again with an E/W loading.

 

[Woody Stover]

Huh. I figured you had the digital probe closer to the flue exit, since it always read higher, but it's actually a couple inches higher than the condar probe. What gives??

 

[RIMatt]

@begreen I would love to see this done as E/W. I've been getting good results with my Enviro Boston unit but since it is the 1200 model Im limited to E/W. The issue I have been having is that the logs at the back of the firebox are not catching. They char up but that's about it until I rake it forward after the logs that had been in the front are down to coals. Any ideas as to why? Thanks.

 

[begreen]

I'll try to remember doing this with a fire in a day or two. Right now we have been burning 24/7 with relights off of hot coals.

 

[BigJ273]

Has anyone used the Auber digital thermometer with the magnetic probe attachment U attach to the stove? Thinkin bout getting one to keep an eye on stove temp. Not pipe temp.

 

[Kobuk]

I've owned the Alderlea T5 for 5-6 years now at our cabin up here in Alaska. When we show up in the winter it can be pretty cold inside and it takes quite a while to heat up a cold building. I get my fire going pretty good and hot but only use the stovetop temp gauge and visual for adjustment. It seems that I run mine quite a bit hotter than the example above. I burn what is on my property which is a mix of birch and spruce. I have been wanting to install a flue temp probe to go along with my stove top temp gauge. My issue and question is about placement. I have a double wall pipe with the slide adjustment. It sounds like the probe needs to be 18"-24" up from stove and I am only able to put it about 10-12" up because that is where the pipes slide together. Will that work? Why do most install higher? Thank you for all of your help on this. I have enjoyed this forum for quite a few years now.

 

[begreen]

The reading will be a bit high that close to the flue collar. It sounds like you are doing fine. In colder weather I push our stove higher. If it was 15º colder I would have been burning hardwood with a peak stovetop temperature of 700º.

 

[Kobuk]

I can't imagine trying to drill my holes through the adjustable area, slide up to clean out my pipe then get those holes realigned! I've thought about it because I think it would be very helpfull to know the flue temps. I've also wonded if putting it lower would be worth it or just freak me out if it reads higher. Every trip down this year it's been pretty chilly, lows around 10-15 below and highs in low single digits. That stove feels real nice!

 

[TradEddie]

That top picture is almost exactly how I do cold starts, I will usually use more kindling, and perhaps one or two pieces of larger kindling. I also throw a split into that gap once everything is burning well. The point about stovetop temperature lagging secondary combustion temperature is especially important in top-down starts with lots of kindling, I get strong secondary flames and no smoke out my chimney long before the stovetop reaches 400F. On hot reloads that lag isn't there, I suspect this is partially because the stove mass is already warmer, but also because hot reloads are a slower ramp of heat to the metal compared with the blast of kindling flames right under the tubes.

TE

 

[MoDoug]

I'm new to wood stoves, I've got about a month under my belt now. Starting fires the old school way with kindling. For my first fire about a month ago, I started the fire then added about 5 splits onto it, in short order my stove top temp was reaching 700 degrees, anxiety set in, with panic a step away... I closed down the air as much as I could, it settled down, then I settled down. Now I'm gun shy, but I've got to say I'm fascinated with your top down burn. I imagine the top down burn can be compared to back burning a field of dry grass. Light it down wind and let it work it's way back, which is true in the stove as well. It will be more controlled and slower, not a run away fire.

My stove is smaller with a 1.8 cubic foot firebox, with E/W orientation. I read somewhere here, I'm pretty sure it was you begreen on an old thread, that with E/W loads you need to be careful with the wood falling against the door/window as it burns down and shifts. Any recommendations to avoid that? I look forward to your E/W burn.

 

[Woody Stover]

I started the fire then added about 5 splits onto it, in short order my stove top temp was reaching 700 degrees, anxiety set in, with panic a step away... I closed down the air as much as I could, it settled down, then I settled down. Now I'm gun shy, but I've got to say I'm fascinated with your top down burn.

If you can slow it down by cutting the air, that's a nice option to have. A top-down start will get less wood gassing at the start of the burn, and burn more slowly as you guessed. You can also cut the air more aggressively at the beginning of the burn. Don't cut it so hard that you lose the secondary burn, though. Larger splits will burn slower as well.

 

[begreen]

I did an E/W start this morning. Will post the details once I get some time in Photoshop to assemble the images and do a write up.

 

[Woody Stover]

I'm fascinated with your top down burn....My stove is smaller with a 1.8 cubic foot firebox, with E/W orientation. I read somewhere here, I'm pretty sure it was you begreen on an old thread, that with E/W loads you need to be careful with the wood falling against the door/window as it burns down and shifts.

You need dry wood for the top-down start to take. With wet wood, the fire will have a hard time working its way down into the load.
Thinking more about the E-W load, you might try putting a big split in the bottom front, and build your top-down on that; The big split should provide a stable base well into the burn, and by the time it burns away, the stuff above that could roll into the glass should be mostly consumed.
My stove is an E-W loader with andirons, so no issue with rolling splits.

 

[MoDoug]

You need dry wood for the top-down start to take. With wet wood, the fire will have a hard time working its way down into the load.
Thinking more about the E-W load, you might try putting a big split in the bottom front, and build your top-down on that; The big split should provide a stable base well into the burn, and by the time it burns away, the stuff above that could roll into the glass should be mostly consumed.
My stove is an E-W loader with andirons, so no issue with rolling splits.

Good info, and suggestion on the big split on the bottom front. All the wood I'm burning was long dead before it was split and covered a year ago, so it's dry. I think I'd turn up the furnace before I ran wet wood through the stove. I googled andirons, and that would be a great addition.

 

[Woody Stover]

All the wood I'm burning was long dead before it was split and covered a year ago, so it's dry...andirons, and that would be a great addition.

Don't try that with Oak. I only harvest dead wood, and Oaks that have been standing dead for five years or more can still be at 30%+ moisture.
I took down a dead White Ash a few months back. It was dead for several years but also metered at 30+ in the trunk. I'm hoping it's some "other" kind of moisture that's not in the cells of the wood and will dry faster, but I have nothing to base that hope on so I'm prepared for the worst. I've already got Plan B and Plan C lined up for that person's wood supply for this fall..

 

[begreen]

Ok, I let the fire die down last night so that I could do an E/W cold start this morning. Note that the T6 has a deep firebox, so I have more wiggle room than some with a shallower firebox, but the general principle is the same. To start with I laid down 2 sleepers about 6" apart on which to lay the E/W splits on. This allows air to get under the wood to assist the fire. Without them, the start would be slower. If there is a hot coal bed then this is not necessary.

Then splits were put on top of the sleepers with one large split in the front to act as a base. The loading needs to be biased toward the rear of the stove so that splits can't roll forward. This means that the wider edge of forward so that the wedge shape of the split is toward the rear. The rear is stacked higher and a pocket has been left to accommodate newspaper balls and kindling to start the fire. Then kindling is stacked on top of the newspaper balls (or starter).



This is a sketch of a hypothetical load set up so that the splits won't roll to the rear of the firebox. There is a trough on top for starting with paper (or starter) and kindling. Once the fire is burning vigorously, another split can be placed on top if needed.
Side View:
front of firebox rear wall of firebox

 

[begreen]

The newspaper is ignited and the kindling starts burning. At this point the door is slightly ajar to admit more air and of course the air control is wide open.

 

[begreen]

The kindling fire is now burning robustly. Time to latch the stove door closed.

 

[begreen]

A split is added on the burning kindling to fill the gap, but not smothering the fire. Note that the fire is now also burning under the logs between and including the sleepers.

 

[begreen]

Time to close the air down to 50%.

 

[begreen]

Secondary burn is good, time to close the air down again to about 25%.

 

[begreen]

Stove is now cruising, air closed a bit more to ~15%

 

[begreen]

Epilog: This is the first E/W fire I've done this year. It was definitely a slower start with more tweaking than my normal N/S fires. The stove needed to be reloaded after 7 hrs. which is shorter than normal, but somewhat expected due to less wood loaded as compared to N/S loading.