Secondary burn tubes, glow or not?

[Rhone]

I was able to remove the sound from my videos. In a previous post we were talking about if the secondary burn tubes need to be glowing to burn secondary gasses since, to burn them it has to be 1100F+. I wanted to show the difference between my burn tubes glowing red with secondary burn, and when they're not. Here's the video's and, I don't know how the sound got converted to Congo drums but it's more enjoyable than my wife yelling at me as they were originally.


Here's my secondary burn when the tubes are red (notice short blue flames on them)
Here’s the link when they’re not (no blue flames anymore)

As you can see, when they're glowing red I get blue waves of flame against the secondary burn tubes. When I turn my air down a little, as you can see by the speed of the flames they're not much different (I've mastered at what position the air handle needs to be). In about 5 minutes the tubes stop glowing and I slowly start losing those blue flames on the tubes until it looks like a normal fire. Your thoughts if the one with the blue is secondary burn going on and tubes should be glowing?

 

[Roospike]

Thanks but ..................I wanted to hear your wife yelling at you in the back ground!

Rhonemas , can you start a thread on that!?!? PLEASE ! ;-P

 

[citizanken]

Mine does the same thing Rhon, but I figured it was just the damper effect of closing the air off some. Kinda like a huricane to a breeze.

 

[jqgs214]

I've been thinking the same thing. Can secondary burn be going on without the presence of flames around the tubes???

 

[Todd]

Any difference in what comes out the chimney between the two burns?

 

[Rhone]

The best answer is, that whether the burn tubes are glowing or not there usually isn't smoke out the chimney unless I turn it as low as it will go which usually smothers the fire. So the blue flames at the burn tubes aren't a role in smoke out the chimney.

They are a HUGE impact on heat output and how quickly the unit heats up. Last night, I got the tubes glowing red in just 30 minutes from a cold start and in 45 minutes the unit was throwing out TONS of heat. That's a new speed warm up record for me. Without those blue type flames at the burn tubes takes me 1.5 - 3 hours before the unit warms up. There isn't a big difference in the air setting, and as you can see the flames aren't going very fast. That's about a 6 hour burn there with the blue flames, and close to a 7 hour burn the one without. I can set it as low as 10 hours, but it smothers that low.

I've found my house is consistenly warmer if I get the blue flames on the burn tubes. For example, having the blue flames and burning for 6 hours my house will be 2F warmer in the morning consistently than when I set it to a 7 hour burn and don't have them. I'm curious if others have seen them and experienced similar results, and those little blue flames are what secondary burn actually is. I originally thought, it's when you get that burning floating cloud at the top and kinda spooky looking but, I'm having second thoughts now as to what it really is.

 

[Gunner]

I have a burn chamber instead of tubes but I don't think they have ever been glowing red, and I've gone as high as 800 deg stove top. I will have to check for sure next time it is really crankin.
I think as long as you have combustion of gases above/independant of the load, you are in secondary burn territory. The spooky- floating- rolling cloud qualifies IMO. I set my air as low as it will go while still maintaining continuous secondary, and sometimes get a second opinion by confirming no visible smoke from the chimney.

 

[citizanken]

Brother bart had a good explanation of the secondary burn somewhere in this post I read a while back.

https://www.hearth.com/talk/threads/5564/

I hope this is helpful Rhon. I think the secondary is still going on, but it is at the log level, not at the tube level.

 

[Gooserider]

My understanding is that when you have the blue flames off the tubes like a gas burner, it means your firebox is full of hot combustion gasses, and the ignition is mostly occurring right as the oxygen is coming out the tubes into the box.

When you don't have the blue flames, you might still have secondary combustion, but it is occuring lower down in the firebox because you don't have quite as much combustion gas, and the oxygen travels further into the box before it meets up with enough gas to burn.

This is consistent with the notion of getting more heat faster when you have the blue flames, along with a shorter burn. It means you are charring and gasifying the logs faster, producing more combustion gasses, but the faster burn won't last as long.

Gooserider

 

[NFreiermuth]

My Hampton almost always, has red, glowing, secondary burn tubes.

I have rarely seen it secondary burn without the tubes slightly glowing, or fully glowing. At least in my situation, the gases burn immediately after the secondary tubes. Since the tubes cascade from the rear to the front (five of them), the previous one heats the one in front of it. The flames almost look like a bluish orange colored flowing river towards the door. Then, the air wash pushes them down towards the coal bed. The wood looks like it's evaporating until it finally turns into a red coal itself. When this happens, the secondary burn dies out, and then it's time to feed it again.

Sounds like what Rhonemas was describing. Once it looks like a regular pre-EPA woodstove fire, I don't think the internal temps are hot enough to combust the gasses in the fire box. At least, from what I'm used to seeing.

 

[Gunner]

Maybey the thickness of steel used in the tubes has to do with it.

 

[the_guad]

Forgive my ignorance, but everyone has told me to make sure that the stove ISN'T glowing red. What's the difference between an overfire and your secondary tubes glowing red?

 

[Rhone]

The main difference is that your secondary tubes are designed to get/be over 900F without damage and it's pretty common to have your secondary burn tubes glowing red but having the your stove surface be only 500F. The tubes are made out of stainless steel to ensure they can take the heat and have insulation above them to get them as hot as possible so they do end up frequently glowing and that's normal. I guess it's like the difference in seeing a burner on your kitchen stove glowing red, vs. seeing your entire kitchen stove glowing red. Maybe that's not a good example but you get the point.

 

[Harley]

I guess it's like the difference in seeing a burner on your kitchen stove glowing red, that's perfectly normal vs. seeing your entire kitchen oven is glowing red.

Uh, Oh... the whole oven's not supposed to glow red??? That could explain that overdone meat loaf the other day!!

 

[citizanken]

I think Todd had a point, look to the chimney output. If it is the same, with the glowing tubes, and without, then either there is no gasses to burn off, or secondary burn is indeed occuring, but at log level.

 

[the_guad]

Thanks for the clarification. I didn't realize that the secondary tubes would be made out of a different material. Guess I should have figured that one out on my own. I think I would freak out if my whole insert were glowing red.

 

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My VC Aspen gets the Blue Flame at the tubes but thy never glow red