Rules of thumb for the progress hybrid air inlet and bypass damper

I'll take a crack at this, but others may correct me. I've ran my PH last spring and the start of this year. So some experience.

Regarding the screen, I don't worry about it glowing at all. I was running last night about 400 degrees stovetop and it had a slight glow.

I also wait until the thermometer is in the white before engaging the CAT by closing the damper. If it keeps smoking, open her back up for a while. But learn the difference between smoke and vapor. In the right circumstances I've seen white "smoke" that was vapor..... Like seeing your breath on a cold day. Vapor is very white and will dissipate quickly.

I have been playing with closing the air down quicker, before engaging the CAT. That keeps more heat in the stove and seems to heat it up quicker. This, of course, is after the wood is good and lit. It's counter intuitive to me, but more air lets the heat escape up the flu. Less air will keep it in the firebox longer.

That's my take. Others will chim in I'm sure.

georgepds said:

I'm working out some rules of thumb from my woodstock progress hybrid. I spent ~30 years with a smoke dragon, and I need to get the hang of the multiple damper bypass setup. The stove is connected to a insulated steel chimney that goes straight up the inside of the house with about 25 feet between firebox and top

My big "worry" is over firing the stove.. and so far I've never even got close ( judging by the surface thermometers) I have a surface thermometer on both the stovepipe and the wood stove top.

First rule of thumb.. wait until the temperature on the stove pipe moves from the black to the white area ( I think it is 350 F) before closing the bypass damper to engage the cat ( usually takes about 30 minutes from a cold start)

Second rule of thumb.. if after engaging the cat, you see/smell smoke coming out the chimney outside, disengage the cat and let the fire burn hotter for a while

Third rule of thumb.. no matter if cat engaged .. if the little metal screen above the fire box starts to glow red.. turn down the main air damper

I wonder what others use as their clues ?

The smoke out the chimney was a big clue to me that the cat was not working.. best guess ..it just was not cold enough outside to draw enough air through the cat.. could be wrong here

I'm not sure if it's OK for that metal screen to glow red, so I avoid it. If it's ok let me know

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In my experience, this is generally correct. I believe the thermometer changes color at 250 degrees, not 350. There have been several changes to the PH design since I got mine initally in 2011, so the "cat engagment" temperature has chnaged several times for me. I generally find that if I engage the cat as soon as the thermometer reaches the white area, it is too soon. But generally I engage it somewhere between 275 and 325 if possible. It obvioulsy also depends on where you place your thermometer--mine is on the top of the cast iron of the back part of the stove. If you wait too long and the stove gets too hot, the secondaries will light off prematurely and you will get shorter burn times. Ideally when the cat lights off you want to be staring at a black box that is really hot with no or few flames.

The screen glows sometimes--it is steel and it is desingned to take the heat--no issue there that I am aware of.

I generally start the air at 1/2, then close it in stages to 1/4, 1/8 (engage cat), wait a few minutes, then fully close the air. I'm generally like you--it usually takes me about 30 minutes to get the cat up to temp.

You don't need to "worry" about how hot the stove is getting as long as it is not over 600. As far as my peak termperature, my PH generally stays in the 400-550 range.

The screen is made of Iconel and is supposed to behave like a "pre-cat" which helps to incinerate some of the particles before reaching the cat. Mine glows very often during the burn cycle.

georgepds said:

My big "worry" is over firing the stove.. and so far I've never even got close ( judging by the surface thermometers) I have a surface thermometer on both the stovepipe and the wood stove top.

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As stated above, over firing is not something you should be over-worried about as this stove can handle stovetop temps of 650* (and likely a bit higher too - I expect they have a margin of error in the specification).

georgepds said:

First rule of thumb.. wait until the temperature on the stove pipe moves from the black to the white area ( I think it is 350 F) before closing the bypass damper to engage the cat ( usually takes about 30 minutes from a cold start)

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That sounds about right. Now, what I have been playing with here is not letting the stove heat up as fast - i.e. aiming for closer to 45-60 minutes after lighting a cold stove. My working theory is that this allows more of the stove to get up to temp (i.e. end up with the whole stove heated up rather than just the fire's primary path with the bypass open).

georgepds said:

Second rule of thumb.. if after engaging the cat, you see/smell smoke coming out the chimney outside, disengage the cat and let the fire burn hotter for a while

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How quickly do you check? I'd give it a few minutes before opening it up. I also have found that if I reduced the air right after engaging the cat sometimes just giving a bit more air can help with this initial smoke. My theory on this one is that if I have a very hot fire going and engage the cat while reducing air too much then all flame leaves the box resulting in "too much" smoke being fed into the cat to burn effectively. Opening up a bit of air lets secondaries in the stove burn some of this.

georgepds said:

Third rule of thumb.. no matter if cat engaged .. if the little metal screen above the fire box starts to glow red.. turn down the main air damper

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Glowing screen is normal and a non-issue in my opinion - call WS if you have doubts and share with us if they advise against it.

georgepds said:

I wonder what others use as their clues ?

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I've gone by temperature (measured there on the cast next to my top exit flue). I won't engage below 250 (the line) and would prefer to engage at 300. IF I see smoke I re-evaluate the situation with air being the first thing to adjust. I've not had issues with temp falling and fire cooling too much if I wait until top temp is 300. I"m sure lots of things are related to what wood (size of splits etc) I am using.

How you operate your air control may contribute significantly to how well the stove performs for you. I used to be rather quick about it - full open to light, about 1/2-2/3 open to cruise up to cat engagement, then 1/4 or so once cat engaged and then move down to fully closed in 10 minutes or so. This year I'm still roughly following this but making more fine adjustments as I lower the air. It has not been all that cold out yet here so draft isn't as strong as I expect it to be later in the year; thus more air required.

I've had mine just shy of a year now, for about 4 total months of winter burning. So, still a pretty new stove. I'm burning seasoned white spruce and Alaska birch.

From a cold start, it takes about 20-30 mins to reach the 250-degree temp. I engage the cat at that point, then play with the air knob depending on whether I'm in the room and want some light, or out of it and want a slow burn. Burning four splits or so, I get a couple hrs of burn time, a couple more hrs of coals, and the stove temp usually hovers at 325-375 on the surface at the rear.

The other day I loaded four birch splits onto a hot bed of coals, engaged the cat and shut the air tight. Got about four hrs of burn and two hrs of coals, and the stove temp went up to about 450 - 500. That's the hottest I've gotten the stove. Pipe temps 12 inches away (horizontal exit) are usually 50-75% of the stove.

siddfynch - How large are those splits? I imagine we have quite some variety in sizes (some consider 16" splits that are 3" on a side a split, others consider this kindling eh?). It would help me to understand your experience better if I can relate to the loads you are using.

Thanks.

Slow1 said:

siddfynch - How large are those splits? I imagine we have quite some variety in sizes (some consider 16" splits that are 3" on a side a split, others consider this kindling eh?). It would help me to understand your experience better if I can relate to the loads you are using.

Thanks.

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Slow, each split is about 1/4 of a 10" x 18" round.

siddfynch said:

Slow, each split is about 1/4 of a 10" x 18" round.

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Your burn times don't sound too bad. I mean, if you put four of those splits in you only had the equivalent of a 10" round in the stove. That's not much fuel. Try loading her up a bit!

hijack alert! Siddfynch... how's that fastball?

johnstra said:

hijack alert! Siddfynch... how's that fastball?

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I'm down to changeups now, but thanks for asking!