Too much secondary air flow

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E

ewlsey

Member
Dec 5, 2014
86
Peoria, IL
I have a small Avalon Pendleton insert. As far as I can tell, there is no air control for the secondaries tube (it only has one).

What happens is the secondary seems to blow like crazy when the primary air is fully closed. This makes sense, since all the draft is now pulling on the secondary tube since it is the only thing open. If the secondaries are really going, it will actually burn holes right through the wood where the holes in the tube are located.

Has anyone put a control on the secondary tube? I think it might increase my burn times.
 
I've done it. It makes the stove top get hotter and coals last longer but no real gains as far as output. I don't know if you want to mess with what has been engineered and tested. Your draft may be on the strong side.
 
ewlsey said:
As far as I can tell, there is no air control for the secondaries tube (it only has one).

Has anyone put a control on the secondary tube? I think it might increase my burn times.
Click to expand...

A few people have modified their stoves, with generally good results, but bear in mind: a modification will void your warranty, and/or may give you worse performance rather than better.

When temps get around zero outside, draft increases. I find I'm getting shorter burn times and substantially higher flue temps in this weather. I have been thinking about modifying my secondary inputs, but have not yet.

The other approach some have taken is to install a pipe damper in the rare event they need to reduce draft. Worst case scenario is you never use the damper, so it makes sense to have one if you are prone to excessive draft.
 
Unless the wood is actually right up next to the secondary air tubes you aren't burning wood, you're burning the gas coming from the wood. I don't see any reason to really modify this, it's doing exactly what it should.
 
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I had the same issue with my Drolet 1.9 . one control ( air intake ) & 28 ft stove to top plate. over draft. nothing to set the secondary air so, I found out where the intake for the secondary air was located on the stove ( lower rear corners ) and used some heavy duty foil tape left over from chimney liner insulation kit and partialy covered both holes 75%. it made a very nice difference . also before that I put a flu damper just above the stove . now I can control the draft and the secondary air . my stove burns very nicely and I get longer burn times without running it to cold. it runs *450 to *600 I am pleased with the changes.
 
thedriver said:
I had the same issue with my Drolet 1.9 . one control ( air intake ) & 28 ft stove to top plate. over draft. nothing to set the secondary air so, I found out where the intake for the secondary air was located on the stove ( lower rear corners ) and used some heavy duty foil tape left over from chimney liner insulation kit and partialy covered both holes 75%. it made a very nice difference . also before that I put a flu damper just above the stove . now I can control the draft and the secondary air . my stove burns very nicely and I get longer burn times without running it to cold. it runs *450 to *600 I am pleased with the changes.
Click to expand...

By doing that you change the way the stove was intended to be used, and also how well it reduces emissions. You're essentially turning an EPA stove into a "smoke dragon". Do you get smoke from your stack when the secondaries are firing?
 
This is not u
ewlsey said:
IWhat happens is the secondary seems to blow like crazy when the primary air is fully closed. This makes sense, since all the draft is now pulling on the secondary tube since it is the only thing open. If the secondaries are really going, it will actually burn holes right through the wood where the holes in the tube are located.
Has anyone put a control on the secondary tube? I think it might increase my burn times.
Click to expand...

This is not uncommon, especially if the firebox is packed full up near the secondaries. I wouldn't mess with it. If you are getting large secondary bloom it's because the wood is outgassing rapidly and the secondary burn is both cleaning up the flue gases but also delivery more heat. Thicker splits will help slow down the burn and outgassing speed a bit.

How tall is the flue on this stove?
 
claydogg84 said:
By doing that you change the way the stove was intended to be used, and also how well it reduces emissions. You're essentially turning an EPA stove into a "smoke dragon". Do you get smoke from your stack when the secondaries are firing?
Click to expand...
no , not a bit. only on reload till it's up to temp. there is a balance to everything. also, checked the chimney liner after about 2 cords and nice and clean. very little build up. secondaries are lit enough to burn off what they need to. I am very pleased with the results.
 
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I used to think my nc30 was burning too hot the first year. This year it burns much better mostly due to my improved operation of the stove. If you do modification, do it with magnets so that you can change it as your knowledge and skills of operating your stove grows.
 
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Other stoves will also shut down on the secondary air when the primary is turned down. I've been looking at some Pacific Energy inserts that work this way.

I can't really have a stove pipe damper since this is a insert.
 
mol1jb said:
I used to think my nc30 was burning too hot the first year. This year it burns much better mostly due to my improved operation of the stove. If you do modification, do it with magnets so that you can change it as your knowledge and skills of operating your stove grows.
Click to expand...
I am far from an expert but, my knowledge and skill of operation is what helped me figure out how to make the stove work better for me with no stove adjustment for the secondary air as well a an over draft from a warm inside and tall chimney. the magnets is a great idea thanks.
 
BrotherBart said:
Well, it is that time of the season...

http://www.gulland.ca/florida_bungalow_syndrome.htm
Click to expand...

Always worth re-reading... thanks.

In summary:
"The real problem is that some EPA certified non-cats don’t provide enough control over the firing rate because their manufacturers must optimize stove performance to pass the emissions tests, the conditions of which duplicate ... a very short chimney and very high outdoor temperature."
 
I thought they were tested with a 15 ft chimney. That doesn't seem very short.
 
I know of no other fuel burning device that does not provide for optimizing performance. Yeah, you have to knock off the limit caps on carburetors but even then a shop is authorized to do that. Not so a stove shop being allowed to modify the unrestricted intakes on a wood stove.

Said it before, the EPA does not care if your house burns down. Just that the stove wasn't smoking when it happened.
 
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begreen said:
I thought they were tested with a 15 ft chimney. That doesn't seem very short.
Click to expand...

I think when JG says "very short" he means relative to chimneys of those experiencing high burn rates in cold temps, many who probably have chimneys in the 20-30 ft range. And if a stove manufacturer suggests a chimney of at least 15' then that would certainly be considered very short by their standards, since that's basically the zero limit... if you used that as a starting point, then you couldn't get ANY shorter and still qualify it as a viable chimney, pretty much making 15' "very short" by definition!
 
ewlsey said:
Other stoves will also shut down on the secondary air when the primary is turned down. I've been looking at some Pacific Energy inserts that work this way.

I can't really have a stove pipe damper since this is a insert.
Click to expand...

Only the pe does that, afaik, and only on the t5 sized box. By design almost all noncat stoves offer very little control.
 
The larger Summit and T6 has secondary control also, though not directly linked. It has a barometric damper on the secondary that only opens up when draft is at its strongest, during the peak of the burn. During the coaling stage the secondary is more restricted.
 
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