New guy with new stove...in a bit of a quandry, perhaps

[GrantC]

Hello!

I recently "upgraded" my 25-year-old Solar Key stove to a new Lopi Endeavor - hoping to reduce significantly the amount of wood I have to split and stack!

It was installed a few days ago, and after burning it I have some questions...maybe concerns, I'm not sure!

We're burning some broadleaf (Oregon) maple, which admittedly isn't the best hardwood in the world. In the old stove, flue temps during a normal sustained burn would be 400-450 degrees, but would flare to 600 deg when starting up. This new stove is significantly cooler, at least in terms of the flue temp - it tends to burn in the 275-325 range, though I was able to get it up to 400 deg one time.

What's more, it doesn't burn this maple completely like the old stove did. For instance, after 6 hours of burning the old stove would have a small pile of red coals and a lot of ash. The Lopi instead will have a 4" deep pile of charcoal, the top layer being red but underneath those it is "cold" black. It just never seems to burn to pure ash, even when left overnight. (This is with the secondary burn "on" and the air control "full".) It certainly has enough coals left overnight to start a new fire, though!

Finally, closing the air control even a bit causes the flue temps to drop below 250 deg, meaning I can't close it for a slower burn without getting into creosote formation territory.

Is there something wrong with the stove or its installation, or do I need to adjust my techniques/expectations with this new technology?

-=[ Grant ]=-

 

[jtp10181]

How long has your wood been split and stacked? How large are the splits you are burning?

 

[BrotherBart]

First thing is are you talking about internal flue temps or is that what they are showing on a magnetic surface mount thermo on the pipe?

 

[GrantC]

1) Split & stacked last March (though there is some moisture under the bark - the tarp blew off the pile a couple of months ago, before I moved it into the dry barn.)
2) Most of them would stay in a 5" circle.

Keep in mind that we just took the old stove out, and so the wood quality is a constant.

-=[ Grant ]=-

 

[begreen]

Hmm, you shouldn't need or be able to run the stove with the air control wide open without it getting very hot. Usually this means an issue with the wood or the flue.

However, I see similar temps burning the same wood on my flue probe thermometer. My first morning burn is always a hot one. When reloading the the stove I also let her burn hot for about the first 10-15 minutes. That usually gets the stack temps up to about 400. The stove top will be at 500-550 depending. Then I reduce primary air by ~50%. You too should be able to reduce the air control to about 50% after the wood is charring on the outside and good secondary burn is occurring. The new stove is burning much cleaner than you are used to, so creosote will be less of an issue as long as you burn dry wood. It's not uncommon for me to see 275 stack temps after an hour or two burning soft maple. But by then secondary burning is starting to wane.

There are many recent threads talking about coals left over in the stove. The question is, how dry is the wood you are burning? how thick are the splits? Also, can you describe the flue system on the stove?

If all the above are as good as they should be -(dry wood, nice flue system, no oversized splits,) then one technique is to rake the coals to the front of the stove, put a small split or two behind them and open the air fully. Let them burn down and enjoy the heat. Another technique is to create two north/south mounds with a valley in between in the center of the stove for the air to travel through. Place a couple medium splits on them and one diagonally crosswise on top. That should take off quickly and will burn hot down to ashes. I tried this yesterday and it worked quite well. (Thanks for the tip Precaud.)

 

[GrantC]

First thing is are you talking about internal flue temps or is that what they are showing on a magnetic surface mount thermo on the pipe?

One of those magnetic thing-a-ma-bobs. (It's the same thermo that I used on the old stove, so the RELATIVE readings are accurate. As to absolute, I don't know.)

-=[ Grant ]=-

 

[jtp10181]

Just because the wood remained constant doesn't mean its good. The modern stoves are much more sensitive to having quality wood.

Are you getting a lot of black on the glass and on the upper sections of the bricks inside?

 

[GrantC]

The new stove is burning much cleaner than you are used to, so creosote will be less of an issue as long as you burn dry wood. It's not uncommon for me to see 275 stack temps after an hour or two burning soft maple.

How low can one go in terms of flue temp without creosote problems with these new stoves?

There are many recent threads talking about coals left over in the stove. The question is, how dry is the wood you are burning? how thick are the splits? Also, can you describe the flue system on the stove?

I've answered the first two above; the flue system consists of 6" pipe from the stove; at 20", it goes through a 45 deg elbow, then a 4" length of pipe, then another 45 angle into an adaptor that takes it up to the 8" Metalbestos pipe. (The angles were necessary because of the differences between the new and old stoves, in terms of where the flue exits.) The Metalbestos pipe is approximately 8-9' long, capped with a rotating ("wind sock") type of cap. Total flue length would be in the 13' neighborhood.

If all the above are as good as they should be -(dry wood, nice flue system, no oversized splits,)

What size splits should I be using? What I've got is what experience showed me was good with the old stove.

then one technique is to rake the coals to the front of the stove, put a small split or two behind them and open the air fully. Let them burn down and enjoy the heat. Another technique is to create two north/south mounds with a valley in between in the center of the stove for the air to travel through. Place a couple medium splits on them and one diagonally crosswise on top. That should take off quickly and will burn hot down to ashes. I tried this yesterday and it worked quite well. (Thanks for the tip Precaud.)

Thanks - I'll try those tips.

-=[ Grant ]=-

 

[GrantC]

Just because the wood remained constant doesn't mean its good. The modern stoves are much more sensitive to having quality wood.

That would certainly explain the problem!

Are you getting a lot of black on the glass and on the upper sections of the bricks inside?

No, none at all.

-=[ Grant ]=-

 

[begreen]

The flue is a bit on the short side. Lopi lists 15 ft minimum. The pair of 45's is also creating a reduction in draft. Sounds like it could use more pipe.

Splits will vary with the stove, but if you want to keep coaling down, maybe no more than 4-6" thick?

The temp of the flue vs creosote production has a few variables. Mostly you want the exiting flue gas temp to be above ~250 when in the early stages of the burn. Once the wood has stopped outgassing, there is little to condense.

 

[GrantC]

The flue is a bit on the short side. Lopi lists 15 ft minimum. The pair of 45's is also creating a reduction in draft. Sounds like it could use more pipe.

I just looked at the installation guide (it was dealer installed, which my insurance company required.) Lopi measures from the floor to the chimney cap, and using that measurement my system is between 15' and 16', with the draft-inducing cap.

I could add another section of Metalbestos pipe, but that presents 2 problems: 1) I'd need to add a roof brace (which, according to the company that makes the stuff I should have anyhow), and 2) it'll making cleaning the chimney more difficult (because the top of the pipe will be well above my head when I'm standing on that section of the roof!)

If it'll help, though, I'll do it...

-=[ Grant ]=-

 

[jtp10181]

Sounds to me like the wood is good enough, no causing black soot on glass and bricks. Problem is more likely to be the flue setup. The combo of 45's plus going into an oversized (8") flue, AND its not very tall. You probably have minimal draft which is why if you choke the air down the fire wants to go out.

What is going on up on the roof?
How steep? How much chimney pipe sticks out of the roof?

 

[begreen]

The cheapest way to find out if it's the flue is to temporarily add a 4 ft. piece of galvanized duct pipe to the flue. If the stove starts behaving like a different animal, you'll have your answer. If it works, you'll need to make it permanent with the metalbestos and bracing. One brace for every 5'+ of pipe.

 

[GrantC]

Question: since adding 3' or 4' of pipe will make it impossible for me to reach the top of the pipe (I may not even be able to reach the cap at that point), do you have any tips? Can the top portion of pipe be removed at cleaning time, or is that a no-no?

-=[ Grant ]=-

 

[GrantC]

Sounds to me like the wood is good enough, no causing black soot on glass and bricks. Problem is more likely to be the flue setup. The combo of 45's plus going into an oversized (8") flue, AND its not very tall. You probably have minimal draft which is why if you choke the air down the fire wants to go out.

What is going on up on the roof?
How steep? How much chimney pipe sticks out of the roof?

Not very steep (I haven't measured it), and the top of the pipe is 6' above where it comes out of the roof.

-=[ Grant ]=-

 

[jtp10181]

I would definitely try BeGreens idea about extending it temporarily. I don't see why you couldn't take off the last pipe section to clean it. You can also clean it from the bottom up.

 

[Todd]

I wouldn't do anything yet til you get more familiar with your new stove. You only had it a few days and there is a big difference in burning between an old pre EPA stove and a new one. You need a couple weeks of trial and error. What are your stove top temps? On EPA stove the stack temps usually run lower than the stove top temps. For example, if your stove top is cruising at 500-600 your stack temps could be 300-400 external.

 

[jtp10181]

I wouldn't do anything yet til you get more familiar with your new stove. You only had it a few days and there is a big difference in burning between an old pre EPA stove and a new one. You need a couple weeks of trial and error. What are your stove top temps? On EPA stove the stack temps usually run lower than the stove top temps. For example, if your stove top is cruising at 500-600 your stack temps could be 300-400 external.

Good point, I did read that he only had it a few days but overlooked that when suggesting things.

 

[swestall]

One question is what was the old stove? Many of the older stoves were designed with looser draft tolerances and would suck air in, produce a fair draft and burn hot in larger or marginal chimneys. The newer stoves are designed to closer tolerances and need a better draft with a flue matched to the stove. This gives rise to the questions of wood because the same wood will produce different results in different stoves; esp a Classic vs modern EPA type stove.
Then there is the learning curve. Some of the new stoves will take a bit longer to get ripping and you have to leave them open to get there.

 

[GrantC]

Thanks for all the replies, and from today's experience Pyro may have "nailed it." Taking what I've learned here, and playing with it a bit, has resulted in really hot burns.

BeGreen's tip about making a "valley" in the coals turned out to solve the coaling problem - we're getting good, clean burns now. (So clean, in fact, that I haven't had to scoop the ash out yet, and this while burning 16 hours a day!) This lead me to realize that this stove is far more picky in terms of airspace between wood pieces than the old stove. Cutting smaller splits and stacking them loosely, criss-cross style with the valley underneath, results in far better burn times and much better output.

This stove is much different than our old one, and definitely takes getting used to!

-=[ Grant ]=-

 

[DriftWood]

What's more, it doesn't burn this maple completely like the old stove did. For instance, after 6 hours of burning the old stove would have a small pile of red coals and a lot of ash. The Lopi instead will have a 4" deep pile of charcoal, the top layer being red but underneath those it is "cold" black. It just never seems to burn to pure ash, even when left overnight. (This is with the secondary burn "on" and the air control "full".) It certainly has enough coals left overnight to start a new fire, though!

To really get a modern stove going it is going to take some learning. This video will set you straight on the handling of a secondary burn tube stove.

This video helps kick the heat out.

http://www.ec.gc.ca/cleanair-airpur/default.asp?lang=En&n=8011CD70-1