Can you get secondary too fast?

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ADK_XJ

ADK_XJ

Feeling the Heat
Nov 18, 2014
325
Saratoga Springs, NY
Been very fortunate (well, it took planning and effort) to be burning very nicely seasoned wood this year. I also did a modified block-off install. Thanks to that combo, I'm able to reach secondary burn much faster than last season and, therefore, close down the air much quicker.

My question is, is there any reason not to do this as quickly as possible?

For example, last year it was more like an hour long process of painstakingly reducing the air control down and could never really shut it all the way. Now, on a restart for example, I immediately close to halfway when full flame occurs and then I take it down to 1/8th and kick on the fan when the stove top hits 300. This has been taking 15-20 mins in comparison and then top temp slowly but steadily climbs to 450-500 before leveling out after I close down the rest of the way. I have a load of 4-5 pieces in a modified NS/EW arrangement and I am maintaining healthy flames. Am I possibly throttling my heat output at the expense of burn time?

My take is that it's working quite well but it's so fast it makes me wonder...
 
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Agreeing with Edyit . . . sounds like better fuel = faster times. Unless you're using something crazy like gasoline to achieve rocket like (and incredibly dangerous) times I think you're doing well . . . I typically take anywhere from 20-45 minutes before I can walk away from my stove. A lot depends on the wood and whether it's a cold start or a reload.
 
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Now, as a follow-up...is closing the air completely too little air for an overnight burn? What if I'm still getting strong secondaries with it closed?

Experimenting with this tonight, stove is currently climbing into the high 500s on the final load of the night and I just closed the air. The burn tubes are glowing in the center...
 
I don't know of any stove but a cat that burns right overnight with the primary air shut all the way down. It seems to be some kind of goal for folks here but I burn with about a quarter of the primary open all night long. When the gases that make that nice secondary burn work are gone there needs to be some primary air coming in into the load to burn the rest of the wood and keep the coaling stage hot. And since primary air is the airwash over the glass in EPA stoves it also keeps the glass from crapping up all through the burn cycle.
 
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BrotherBart said:
I don't know of any stove but a cat that burns right overnight with the primary air shut all the way down. It seems to be some kind of goal for folks here but I burn with about a quarter of the primary open all night long. When the gases that make that nice secondary burn work are gone there needs to be some primary air coming in into the load to burn the rest of the wood and keep the coaling stage hot. And since primary air is the airwash over the glass in EPA stoves it also keeps the glass from crapping up all through the burn cycle.
Click to expand...
Interesting and logical take. I just checked back on my stove and it still is in "light show" mode with heavy swirling secondaries. Is it possible "closed" on my air control rod still allows some primary air through for that very reason?

Or there's enough captured gasses in that closed system to do this for some time...
 
It depends on the stove and draft. Our air control can go to the stop and burn fine with a load of softwood. The primary control does not close all the way. It still admits air for the airwash and the secondary air is unregulated. This is typical of most stoves. Some PE stoves (not our older T6) have regulated secondary supply as well.
 
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They all do let some in even when closed. That is how they pass the EPA test of not being dirty burning when shut all the way down. But the EPA test uses nice clean perfectly dried wood with a specific chimney etc, And doesn't care about heating your house.

Give it a try shut down all night. But keep an eye on that chimney.
 
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Great feedback, I will do just that - test tonight and see how we fare come early AM. For right now, it's burning excellent but I've been running it for 3 nights straight so it should be fairly easy to compare the overnight performance and coaling.
 
BrotherBart said:
When the gases that make that nice secondary burn work are gone there needs to be some primary air coming in into the load to burn the rest of the wood and keep the coaling stage hot.
Click to expand...
I came to this conclusion as well. And I want a decent amount of warm air making it's way up the chimney while burning down.
 
Yeah it is why most folks seem to be able to just load it up and be in bed in 20 minutes. But it always takes me an hour to have it settled in for the night. Every load is different and takes different tweaks before I a can walk away from it.
 
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This weekend I loaded up with 4 year old yellow birch and ended up with a fantastic secondary show, had to shut primary right off to bring the flue down to steady 600 deg. Sometimes i hit on some perfect splits that almost ignite before they hit the coals. But after a while I cracked it back open just a bit. I do like to leave the air @ 1/8 open typically for the long burn. Like BB, I will take some time getting it there before I lay down for the night.
 
We close our stove completely at night, and at most other times. A 28 ft chimney combined with the high winds we get can lead to a runaway stove. We usually are burning wood that is around 20%, and it usually takes me about an hour to get everything where I want it for the night.
 
Similar experience here - we have a catalytic fireplace insert and even when turning down the primary "all the way" plenty of air is still getting in. The secondary air enters the firebox near the bottom in the front, and does not have a direct lever control. However, there is a metal restrictor plate thaT can be moved by loosening some screws to adjust the size of the opening for the secondary air (what PE and Regency - among others - call 'boost air'). I have experimented with various amounts of boost air and found that leaving a smaller opening for the boost/secondary air is the best balance. Even with the boost air closed completely and the primary air turned all the way down there is still enough air to maintain some yellow flame - no smoke from the chimney. It does take longer to light and warm up with decreased secondary air - it's a slower burn. The cat temp will cruise at 1000-1250 with full boost air, and about 700-900 with no boost. I have been able to re-light after 24 hours on hot coals, but normally I do a 10-12 hour cycle at night at 6-8 during the day. And this is with a non-insulated chimney liner in an external masonry chimney. Somehow we are just lucky with our draft - never get any smoke puffing into the house.
 
ADK_XJ said:
Now, as a follow-up...is closing the air completely too little air for an overnight burn? What if I'm still getting strong secondaries with it closed?

Experimenting with this tonight, stove is currently climbing into the high 500s on the final load of the night and I just closed the air. The burn tubes are glowing in the center...
Click to expand...

It depends . . . largely on the fuel and draft.

This time of year I cannot close the air control all the way without sooting up my glass, but in a month or so with wells seasoned wood I can do just that . . . of course closing the air all the way still leaves some air coming in.

I do recommend waiting a bit once you close the air all the way -- if you do so -- sometimes I have closed it off too soon and it chokes down the fire too much.
 
Mine has the doghouse air that feeds the coals when primary control is closed 100%... but I notice with the blower on (low) the firebox cools too fast to leave the primary closed indefinitely. Stovetop temps will steadily drop from mid-500's down to mid-300's over 30min or so. I typically push (open) the damper back in 3mm or so to cruise with the blower on.
 
firefighterjake said:
It depends . . . largely on the fuel and draft.

This time of year I cannot close the air control all the way without sooting up my glass, but in a month or so with wells seasoned wood I can do just that . . . of course closing the air all the way still leaves some air coming in.

I do recommend waiting a bit once you close the air all the way -- if you do so -- sometimes I have closed it off too soon and it chokes down the fire too much.
Click to expand...
Yes, I waited to make sure I hadn't closed down too far, too fast but it seems ever since I did the block-off plate that the stove produces consistent secondary combustion at a much lower temperature / quicker timeframe.
 
ADK_XJ said:
Yes, I waited to make sure I hadn't closed down too far, too fast but it seems ever since I did the block-off plate that the stove produces consistent secondary combustion at a much lower temperature / quicker timeframe.
Click to expand...

yeah that should give you an idea of how much heat you were losing up the chimney without it. between getting warmer faster with the block off plate and burning better seasoned wood the secondaries should definatley fire sooner
 
Really helpful feedback from all. So, I'd say my test of "closed" air control last night was fairly successful as the house was still in the mid-60s when I woke up (low 20s outside) at 6am and the stove itself was closer to 200 then it had been previous nights when I left the air control open 1/8th.

EDIT: Should point out, these are not full loads of wood but just 4-5 pieces of ash/maple arranged sort of NS/EW "log cabin" style. Have not seemed to need a FULL load overnight just yet.

I think the biggest difference I noticed was in the quality of coals left in the box. It wasn't that there was necessarily more of them but that they were still so hot that they lit off a couple of medium sized splits of ash without even adding kindling. Up until this test, I usually needed to add some small pine kindling to the coal bed to get a load started back up.

So, my conclusion is that closing down all the way (at least on my Regency i2400) does not completely cut off the supply of air and, if done while maintaining good secondary flames, can be beneficial for an overnight burn.

The thing I will need to keep an eye on now is how the chimney looks come January when I'll do my "mid-season" clean-out. I did not see smoke when I had the air down all the way but probably best to keep tabs on this approach.

Again, thanks for all the feedback.
 
velvetfoot said:
I think if your glass starts turning black regularly, that might be a bad sign.
Click to expand...
At least after one overnight test (good 7-8 hour burn with "closed" air), that has not happened. I'll keep an eye on it, good point.
 
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