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.
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- A Condar probe thermometer on the double-wall stove pipe.
- The stovetop temperature on a Sandhill thermometer
- 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.
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Fire started, flue temp and stove top temp is <100ºF. Door left open about 1/2".
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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.
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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.
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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.
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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.
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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.
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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.