Enough Draft? Wood quality vs draft?

[avc8130]

How does one know if their setup has enough draft?

ac

 

[begreen]

If it sucks the pants off of ya, it has plenty of draft. :lol:

 

[shawneyboy]

Give the details on your setup and some of the resident experts will give you their thoughts. There is a meter that can be used, but .......

 

[avc8130]

Give the details on your setup and some of the resident experts will give you their thoughts. There is a meter that can be used, but .......

I like this meter idea...I already have both a manometer and a wind meter. Are there some values I can compare to?

My setup (I was trying to avoid this because I want the general answer, and NOT the specific answer):

Jotul Oslo
8" single wall pipe up 3' into a 90 elbow. 6-8" increaser into a masonry thimble into an 8x8 terracotta liner. Chimney is all masonry interior to the house. Single story house, chimney goes up through attic to peak of roof. Chimney extends 3' above roof peak.

I am not having any particular issues, I am mostly CURIOUS. Hence why I am looking for quantitative answer.
ac

 

[avc8130]

How about this one:

Is there a correlation to draft necessary and wood quality? In other words, if you have less seasoned wood does more draft help burn it?

In my setup, I can burn pallet wood and get the stove up to 575 pretty easily with the air set around 1/2. I actually have to turn the air down to reach max temps because at full the fire just rages and the temps don't go up.

With wood that tests to around 20-25% on a fresh split with the moisture meter I was struggling last night to get temps above 400. No futzing with the air was helping.

So...which one is it? Wood or draft?

BTW: I KNOW the answer is going to be "wood"

ac

 

[Battenkiller]

If I peek in the little secondary air hole, a good draft will pull the contact lens off my eye. :ahhh:

 

[LLigetfa]

BTW: I KNOW the answer is going to be "wood"

I guess that's what you call a rhetorical question.

Dry wood is a good cure for poor draft, but more draft is a poor substitute for marginal wood.

 

[branchburner]

Size matters. Small wood burns hotter/faster than big wood, assuming the same MC. So even if your splits were as dry as the pallet wood, it would take longer to get to temp.

The factors of draft and wood (size/dryness) of course have to be balanced with air supply, as you noted. That's the biggie for me in determining temps, as my wood and draft are relatively (!) constant. Tweaking the air, say from 1/2 to 1/4 open, can bring my flue temp from 600F to 300F in a hurry.

 

[branchburner]

Dry wood is a good cure for poor draft, but more draft is a poor substitute for marginal wood.

Well said!

 

[branchburner]

If I peek in the little secondary air hole, a good draft will pull the contact lens off my eye. :ahhh:

And then you won't be able to see the burn mark on your nose.

 

[avc8130]

Size matters. Small wood burns hotter/faster than big wood, assuming the same MC. So even if your splits were as dry as the pallet wood, it would take longer to get to temp.

The factors of draft and wood (size/dryness) of course have to be balanced with air supply, as you noted. That's the biggie for me in determining temps, as my wood and draft are relatively (!) constant. Tweaking the air, say from 1/2 to 1/4 open, can bring my flue temp from 600F to 300F in a hurry.

So maybe I will grab the splits I have and split them again into 2-3" rather than 5-6" across the back bone. That should help?

What moisture am I looking for? I THOUGHT 20-25% was ok.
ac

 

[begreen]

15-20% moisture content is preferable.

 

[branchburner]

I THOUGHT 20-25% was ok.
ac

I never measure, but it seems a 20% range is roughly the turning point for a good burn with some stoves. Going up to 25% may make a big diff.
Forgetting %, how long has your wood been cut/split/stacked, and what species?

I also find that burning a mix, small along with large, helps my stove run best. All big splits and sometimes it won't coal well for my burn chamber. I have some big oak about 24 mos cut and 12 mos split - decided I'm going to give it another year!

 

[avc8130]

I can't get honest answers about how long split/stacked since I did not do the work myself. The wood I have now is a sample from a local supplier to see if his wood would burn well enough for me. I am starting on my personal supply NOW for next winter. I am just looking for something to get me through this winter.

Anyone know a supplier in North NJ selling GOOD, READY TO BURN wood?
ac

 

[LLigetfa]

My chimney height is less than RSF spec's and so my draft marginal. I can very easily tell the difference between one year and two year seasoned wood because one year seasoned is a real PITA to burn. Two year is good and three year is WOWZERS!

I don't own a MM or a digital temp probe, and have no stovetop or flue temp gauges either, just a sense for what is what. In my unreformed years, I would heap the wood for the first year before moving it to the shed and could tell just by picking up a split whether it was a burn it now, later, or much later split and would stack accordingly. The baseball bat sound only takes you so far, the weight being the better clue, but the best clue is how it burns.

 

[Battenkiller]

I already have both a manometer and a wind meter.

Well, since you already have a manometer, might as well put it to good use.

For most wood stoves, you should have a measured draft of between 0.04" and 0.08" of water when the stove is at operating temps. Obviously, there is some room for variance, but not too many stoves can handle a draft as high as 0.12" without tending toward overfire, or below 0.02" without tending to smolder and burn inefficiently.*

As far as moisture content, 19-25% MC (as measured with an electrical resistance type moisture meter) is the moisture range EPA stoves are tested at, so you can't go wrong with that as a starting point. That is the exactly equivalent to 16-20% water by weight, which is what BG suggested.

Besides split size and moisture, you must take into consideration wood density. Dense woods or large splits burn better at lower moisture contents. Small splits or low-density woods burn better at higher moisture contents.

Lastly, but perhaps most importantly, you need to consider how much heat energy is contained inside the firebox. Temperature and heat are not the same thing. A burning match is a hell of a lot hotter than a bath tub full of warm water, but the tub contains thousands of times as much heat energy. A stove needs to have a full and well developed coal bed to get good ignition and cruising burns, especially when loaded with larger and moister wood. Otherwise, the new charge will drop internal temps substantially, lowering flue temps, and reducing draft to a point that no amount of intake air opening will bring more air into the stove. This problem is further compounded by the physical presence of the fresh charge, which serves to impede the flow of air through the stove even more.

During the EPA test, the first phase is to establish a substantial coal bed before the main load is added. Follow their lead and you should see a vast improvement. After all, your stove is designed to burn cordwood of the proper moisture content. Burning pallets is the pits, and can easily lead to excessive creosote formation in the absence of enough air.


* The above information regarding draft was taken from a recent phone conversation with an engineer at Pacific Energy.

 

[Battenkiller]

That's the biggie for me in determining temps, as my wood and draft are relatively (!) constant.

Huh? How can your draft be relatively constant if your flue temp varies?

 

[branchburner]

That's the biggie for me in determining temps, as my wood and draft are relatively (!) constant.

Huh? How can your draft be relatively constant if your flue temp varies?

My draft is good, meaning how my stove drafts in general, versus the actual draft measurement under different conditions. There are two ways of looking at "your draft": the fixed system of your flue size, height, etc. = "your setup"; and the specific draft of an individual burn as determined by wood moisure/size, flue temps, outdoor temps, etc. = "your fire."

So using marginal wood, you can have a bad-drafting fire with either a good-drafting system or a bad-drafting system.

 

[Battenkiller]

... the specific draft of an individual burn as determined by wood moisure/size, flue temps, outdoor temps, etc. = "your fire."

So using marginal wood, you can have a bad-drafting fire with either a good-drafting system or a bad-drafting system.

Draft occurs inside the chimney, downstream of the actual combustion. It's strength is not dependent upon moisture content or wood size, simply upon chimney height and temperature differential, minus the sum of all the resistances in the system (els, caps, pipe walls, etc.).

Are you saying you can't get a good draft with marginal wood?

 

[Backwoods Savage]

BTW: I KNOW the answer is going to be "wood"

I guess that's what you call a rhetorical question.

Dry wood is a good cure for poor draft, but more draft is a poor substitute for marginal wood.

Whoa, LLigetfa got the big post to start the New Year! And the OP gets a big one too because he already knows the answer to his question!


As I've stated many times, if you have a 2-3 year wood supply and keep that amount on hand, your wood worries will be over and you can forget the MM as one will not be needed. You will then be one happy camper because your stove will operate as it was intended to. You will reap the reward with more heat from less wood burned and you will be comfortable in your home, which is how you should be.

 

[branchburner]

Draft occurs inside the chimney, downstream of the actual combustion. It's strength is not dependent upon moisture content or wood size...

I'll quote you: "Otherwise, the new charge will drop internal temps substantially, lowering flue temps, and reducing draft..."
Aren't you saying the draft strength is dependent upon the moisture content or size of the new charge of wood?

 

[oldspark]

BTW: I KNOW the answer is going to be "wood"

I guess that's what you call a rhetorical question.

Dry wood is a good cure for poor draft, but more draft is a poor substitute for marginal wood.

Whoa, LLigetfa got the big post to start the New Year! And the OP gets a big one too because he already knows the answer to his question!


As I've stated many times, if you have a 2-3 year wood supply and keep that amount on hand, your wood worries will be over and you can forget the MM as one will not be needed. You will then be one happy camper because your stove will operate as it was intended to. You will reap the reward with more heat from less wood burned and you will be comfortable in your home, which is how you should be.

There are other reasons to have a moisture meter even if you are well ahead on wood, some times I cut dead trees on my place and I want to know when I can burn them so not as to let the stuff set around longer than needed. I had a dead elm that fell over last spring and it was nice to know how dry it was. Some times I like to check the moisture content for the discussions on here.

 

[LLigetfa]

Some times I like to check the moisture content for the discussions on here.

Ja, but then FUD sets in. Did he resplit and test on a fresh face? Did he stick the probes in far enough? With the grain or across the grain? On the end grain... that's not how to do it!

It gets to be like the conversations on cord measurement. Real cord, face cord, bush cord, stove cord? Then there's the conversation around thermometers... surface or probe? Where to place? Is mine accurate?

I'm just playing Devil's advocate. There is no perfect answer so we work with what we have/know/assume. Do we fly seat-of-the-pants or by the instruments?

 

[NH_Wood]

BTW: I KNOW the answer is going to be "wood"

I guess that's what you call a rhetorical question.

Dry wood is a good cure for poor draft, but more draft is a poor substitute for marginal wood.

Whoa, LLigetfa got the big post to start the New Year! And the OP gets a big one too because he already knows the answer to his question!


As I've stated many times, if you have a 2-3 year wood supply and keep that amount on hand, your wood worries will be over and you can forget the MM as one will not be needed. You will then be one happy camper because your stove will operate as it was intended to. You will reap the reward with more heat from less wood burned and you will be comfortable in your home, which is how you should be.

And each time you say it, it is just as well said! Happy New Year Dennis! Cheers!

 

[branchburner]

Do we fly seat-of-the-pants or by the instruments?

The ability to do both can be the best way to avoid ending up in the drink.