Bi-metallic controlled air intake for the cat.. It's on their blog, pretty interesting read. As the stove gets hotter it keeps the draft from increasing, thus keeping more heat in the stove and less going up the pipe.. Coil spring controlled..
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Huntindog1
Minister of Fire
http://blog.woodstove.com/
The way I take it is at high burn rates the cat is starved for oxygen thus the cat needs more oxygen from fresh air so the bi-metalic coil opens at high burn rates allowing the cat to get some more fresh oxygenated air.
Thus the improvement of cat performance from the extra oxygen improves emissions thus improves the efficiency.
So its actually allowing more air in at higher burn rates. (maybe not read on)
This is a little tricky but I think it has to do with the location they are allowing the air in with the automated control.
Since the automated control air is let in after the cat this changes the balance in the stove. So now with this control opening at high burn rates yes you are allowing more air in after the cat but your fixed draft is not going to now be pulling as much air in thru the primary air down in the main firebox level so your main fuel load down below will be getting less air so your main fuel load is now burning slower increasing your burn time.
Ahhhhhhhhhhhhh this could be the secret to 40 hour cat burns.
The way I take it is at high burn rates the cat is starved for oxygen thus the cat needs more oxygen from fresh air so the bi-metalic coil opens at high burn rates allowing the cat to get some more fresh oxygenated air.
Thus the improvement of cat performance from the extra oxygen improves emissions thus improves the efficiency.
So its actually allowing more air in at higher burn rates. (maybe not read on)
This is a little tricky but I think it has to do with the location they are allowing the air in with the automated control.
Since the automated control air is let in after the cat this changes the balance in the stove. So now with this control opening at high burn rates yes you are allowing more air in after the cat but your fixed draft is not going to now be pulling as much air in thru the primary air down in the main firebox level so your main fuel load down below will be getting less air so your main fuel load is now burning slower increasing your burn time.
Ahhhhhhhhhhhhh this could be the secret to 40 hour cat burns.
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...with this control opening at high burn rates yes you are allowing more air in after the cat but your fixed draft is not going to now be pulling as much air in thru the primary air down in the main firebox level so your main fuel load down below will be getting less air so your main fuel load is now burning slower increasing your burn time.
Ahhhhhhhhhhhhh this could be the secret to 40 hour cat burns.
That sounds about right. Lets hope that's the case.
ridemgis
Feeling the Heat
I read "upstream of the catalyst" in their post to mean that they're providing more air to the cat burn, not after the cat.
aansorge
Minister of Fire
I don't think they would want more air after the cat....must be before. Air to the cat but not to the load?
Tenn Dave
Minister of Fire
Quote from the blog: The intake point for the catalyst air is downstream (after) of the firebox and upstream (before) of the catalyst. As the stove heats up and catalyst air is increased, the flow of primary and secondary air is stabilized, and at high temperatures it is actually reduced, improving emissions, efficiency and burn times.
Kind a sounds like PE's EBT. My take is they are trying to reduce the higher emissions at high burn rate EPA tests thus lowering the overall average emissions.
Interseting, if true this is the exact opposite of the way the Vermont Castings secondary air intake operates. They use a bimettalic coil to control the secondary opening that feeds into the cat inlet hood- but it is configured to be open when cold, and close down (but not completely) as the cat heats up. They use it to feed extra air to help the cat light off.
Huntindog1
Minister of Fire
I think you guys are right the air most likely comes in right before the cat but above the fire box main load.
DevilsBrew
Minister of Fire
- Apr 21, 2013
- 687
In general, where is the secondary air intake added to a wood stove? I am curious because when I was playing with fire I noticed a difference when I added it to the top and back of the fire.
Oldhippie
Minister of Fire
- Dec 18, 2011
- 570
.This isn't a new idea, my 1988 CDW had a secondary air intake to feed the cat too. I never notices that it did much good, but maybe.
Huntindog1
Minister of Fire
There could be lots of new twists to old ideas that were used in the past. The end result will show up when they get the test results back.
In Engineering its really hard once you reach a point to squeeze out a few more percent improvement. A little tweak here or there or a little different twist on an old idea. Its like that cake recipe if you add a little this or that the cake turns out better.
In this situation with the new Steal Hybrid stove. Its a hybrid technology. Having the secondary air manifold thats a fixed air supply it has to provide air up in the top of the stove over a wide range of conditions. So they most likely tune it in the middle so it covers a wide range of fire box conditions like a low burn or a high burn. But like they said at high burn conditions the cat is starved a little for Oxygen. Most likely not much but they are wanting to squeeze out a cleaner burn over the entire burn cycle. So they must have found that during high burns that adding in a little air to the cat cleaned things up more. They most likely have data loggers that record the entire burn cycle and tells them what part of the burn gets a little dirtier.
If the EPA emission numbers weren't averaged over a low, med and high burn I'm sure they wouldn't be doing this. A cat stove burns well below 1 GPH emissions at low burn rates, it's the higher burn rates where the cat stoves get dirtier, probably because lack of combustion air for the cat and the speed of the exhaust through the cat. This tweak should lower and make the EPA number look better but not many people burn their stoves at high burn rates anyways.
When I burn mine high I usually have the bypass open anyway, usually at the start of a fire. I wonder if this stove will be able to cruise at higher temps than the past ones if they are doing all this work for the high burn.
Ashful
Minister of Fire
Leave it to a sailor to know the difference between upstream and downstream.
Huntindog1
Minister of Fire
Todd , I wonder if its more for the high parts of the burn cycle not just burning it, set on a high setting. I think its got do with balance in the stove which makes the main wood load last longer. As even set at a low over night burn setting the stove has a peak it reaches during that cycle. That auto control tones down that peak and spreads out the length of the burn while at the same time giving more oxygen for a cleaner exhaust. In my previous post I was a little mis leading inthat the setup was for when the stove is in a high burn rate setting.
Meh, 3.2 CF is not something I would want to call King. My princess is 2.85. Maybe the Progress Queen? Let's leave some room for improvement to a 4+CF stove worthy of the king label.
I am not concerned with such small improvements to emissions but if all of these imrpovements to emissions result in improvements to efficiency, output, and burn time then it is a worthy pursuit. Be careful of the tradeoffs though, cat stoves are already complicated enough to run.
That makes sense but would it take away from a higher heat output? Not that you really need a 100,000 BTU output stove, I'd rather see those BTU's stretched out over a longer burn.
I think the Blaze Kings are throttled down something like this to achieve their long burns. Compared to similar sized non cats the max BTU ratings are much smaller. I bet if you rigged the t-stat so it could run wide open it may come closer to non cat outputs but may not pass EPA.
I found just the opposite with my Fireview.. I'd get my stove up to temp, close the by pass and set my draft to .75.. Walk away until it needed another load . I found that very uncomplicated and was amazed at how nice the stove was to run.. I'm sure other Fireview owners would express the same views.. Simplicity! I think this is what has created such a big following, the people run the stove, not the other way around..
Highbeam knows, he's just trying to reel in Dennis. They've been having a fued for years over this.
Ok. Now some things make more sense on these Woodstock threads.
Better delete my post before Dennis comes in from splitting wood 
teutonicking
Feeling the Heat
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