Why Are Draft Specs Not Listed By All Manufacturers?

[jbythesea]

The many posts on over-firing coinciding with the drop of outside temperature into the teens and twenties got me wondering. Why don't all manufacturers list a range and or ideal draft that their stove will run at peak efficiency. Particularly these days where they all have to pass epa standards and make pretty finicky stoves. Instead you'll find minimum chimney heights and some vague descriptions of how "over-firing" and "a stove that is hard to control" may be a sign of too much draft.

Most of my searches here are on Harmans since that's what I have. I find quite a few posts where people are saying that their stove doesn't really start humming until the temp drops below 30F. Again, this is a draft thing. I know that Harman manuals are pretty cryptic, but it doean't seem like people mention it for other stoves either. There is some mention of it in the boiler section.

Am I missing something? Is there a universally accepted draft that modern stoves assume? Are they affraid of something? I have a 36'+ stack that can get up to 0.18 inches of H2O on a calm day. So this is something I'd like to know.

While I'm at it, they should also spec the requirements for wood dryness, species etc.

 

[begreen]

There are major differences in the docs from different stove companies (and many other products). Why do only a few list overfire temps or recommended thermometer locations? FWIW, Hearthstone does include draft specs in their manuals.

PS: your draft is very strong. Do you damper it? Most stoves are going to want to have a draft reading between .06 and .1" wc.

 

[EatenByLimestone]

They could make it so you 'd need a phD to read and understand it, and then we wouldn't read it.

You ask for directions when you're lost, don't you. Don't be that guy!

 

[begreen]

From the Mansfield manual:
In general, you do not need to install a stovepipe damper
with the Mansfield. Some installations, however, could
benefit from a stovepipe damper, such as a tall chimney
which can create a higher than normal draft. In such
cases, a damper can help regulate the draft. The
Mansfield requires a draft between 0.06" wc and 0.1" wc.
For drafts above 0.1" wc, install a stovepipe damper.

The quality of your firewood affects heat output, duration
of burn and performance of your stove. Softwoods
generally burn hotter and faster, while hardwoods burn
longer and produce more coals. Density and moisture
content are two critical factors to consider when
purchasing wood for your stove.
The following is a list of wood species and their relative
BTU (British Thermal Unit) content. The higher the BTU
the longer the burn. Firewood with higher BTUs is
generally considered more ideal for a wood stove.
HIGH: Apple, Black Birch, Hickory, Locust, White Oak,
Black Beech, Mesquite
MEDIUM HIGH: White Ash, Beech, Yellow Birch,
Sugar Maple, Red Oak
MEDIUM LOW: Black Ash, White Birch, Grey Birch,
Elm, Norway Pine, Pitch Pine, Black Cherry, Soft Maple,
Tamarack
LOW: White Pine, White Cedar, Balsam Fir, Spruce,
Aspen, Basswood, Butternut, Hemlock
Moisture content also plays a key role in the performance
of your stove. Wood freshly cut from a living tree (green
wood) contains a great deal of moisture. As you might
expect, green wood has difficulty burning and should be
seasoned before using it in your wood stove. To properly
season green wood, it should be split, stacked and allowed
to air dry for a period of one year.
Stack the firewood on skids or blocks to keep it off the
ground, cover only the top of the stack. Plastic or tarps
that cover the sides of the woodpile trap moisture and
prevent the wood from drying. As for stacking, an old
Vermonter said, "The spaces between the logs should be
large enough for a mouse

 

[Hardrockmaple]

.05-.10wc. may be the norm required. My Drolet manual quotes these numbers as well.

 

[jbythesea]

Good to see that there are companies out there listing them.

Begreen - The draft I stated had a small typo. I meant to type 0.16. Still very strong. I do in fact use a damper. Been using a barometric damper for years and love it (despite the shortcomings discusses here). On top of having strong draft, I live between a field and a lake. On a windy day, that thing can get swinging like the bathroom door at an irish pub on St. Patty's Day. I tried the stove without any damper and with a manual damper. Neither one cut it. On calm days, the manual worked pretty well, but when it got windy things got out of control. The baro gets things to run fairly smoothly.

Through trial and error, I've ended up at 0.08 for the Harman. My last stove (an old Noble smoke dragon) liked .06 so I started there and fussed and fussed till the Harman settled down a bit. The Harman is one of the first TL200 Exception stoves. I got it for scrap price at the local scrap yard and rebuilt it. Replaced the AB, AB weldment, damper weldment, all gaskets of which this thing has many. Anyhow, I'd still consider it finicky compared to the Noble or any other stove I've used and proper draft makes a huge difference. That and gaskets. If a gasket leaks, this thing isn't worth the scrap price I paid. The AB will stall, It'll run away etc. Since this thing has more gaskets ready to blow than a losing politician it's always a little hard to walk away from. It has 4 external gaskets (top load door, front door, front door glass, ash pan) and two damper gaskets (one for the weldment and one for the damper itself). These are the really important ones. Then, it's got a gasket around the "shoe", two gaskets on the AB weldment, and two around some other parts that I can't remember the name of. With a real strong draft, any of these that are weak makes problems.

I'm just rambling now. Just wanted to give the background for the post.

 

[branchburner]

Are they afraid of something?

Maybe that potential buyers could be steered towards buying a different stove, based on such specs? Or that potential buyers might see they are getting a stove that is ideal for January/February, but not so much for October/November?

But I would also suggest, more likely and importantly, they do like the option to refuse warranty claims on the basis of overfire. In other words, such specs might complicate their rather simple formula that overfire problems are always user-based, and never manufacturer-based.

It is my belief that the burn technology of a Harman, for example, performs best within a draft range that is a bit on the higher side of what most stoves require. And it is in fact a narrower range, as well, since that range starts closer to the upper limit of what would be acceptable for most stoves. Too low, and the secondary is more apt to stall... too high, and the stove is more likely to overfire.

Trouble is, this downdraft technology tends toward the overfire range in a "normal and "good" hot burn. I have seen the back of my stove in the 800F range, even with primary air shut, as the draft pulls in more secondary air than I would personally offer, if I had any ability to manually control the secondary input (other than stuffing foil in the holes).

You may have noticed a few posts that speak to this overfire problem... though that seems to be more so the case with the Lopi Leyden "Cross-Flow" and VC "Everburn" versions than with the Harman "FireDome".

 

[DanCorcoran]

Most folks don't have a thermometer or moisture meter. I can't imagine that posting draft specs would generate a lot of excitement.

 

[begreen]

Yes, I would expect this number to be in the stove's technical manual, but not in the homeowner version. Still, I do appreciate thorough docs. It's good to know and provides guidance to the homeowner that sometimes is left on their own by the dealer.

 

[BurnIt13]

I've read through a few posts with mixed ideas.....but is draft something the DIY'er can measure? Or is it best to hire a sweep to come do it?

 

[begreen]

If you have the magnehelic tool you can measure it. They sell on eBay.
(broken link removed to http://www.ebay.com/itm/Dwyer-Magnehelic-2001-Gage-Pressure-Gauge-Water-Level-Meter-0-1-00-w-Case-EXC-/141134222840?pt=LH_DefaultDomain_0&hash=item20dc4155f8)

 

[BurnIt13]

Ooooooo. Thats pretty! Now my next question. I know I can find a manual and what not to figure out how to use it, but what is the basic order of operation? Do I need to take apart my stove pipe to install this? Do I have to block off the top of the stove? Do I have to install some sort of port in which to attach this hose?

Thanks.

 

[Hardrockmaple]

Ooooooo. Thats pretty! Now my next question. I know I can find a manual and what not to figure out how to use it, but what is the basic order of operation? Do I need to take apart my stove pipe to install this? Do I have to block off the top of the stove? Do I have to install some sort of port in which to attach this hose?

Thanks.

I had mine checked by a professional (?), all he did was drill 2 holes (to accommodate the rubber hose) for two different test spots,one below the 90 degree elbow and one above it. We started at stove start up and finished at 400 pipe temp. I passed.

 

[jbythesea]

Ooooooo. Thats pretty! Now my next question. I know I can find a manual and what not to figure out how to use it, but what is the basic order of operation? Do I need to take apart my stove pipe to install this? Do I have to block off the top of the stove? Do I have to install some sort of port in which to attach this hose?

Thanks.

I have a Dwyer Mark II mounted to the wall near to the stove. It required drilling a small hole about 3/16" in the side of the stove pipe (single wall). I just stick the hose into the hole and check it when I feel like knowing. At first this was constantly. Now I do it once in a while to make sure that the baro is still functioning ok. If you have a baro, you don't even need to drill a hole. Just stick it in the draft control an inch or so - assuming it's being pulled open by the draft. If you do this, just avoid touching the draft control or you'll throw off the reading.

 

[jbythesea]

It is my belief that the burn technology of a Harman, for example, performs best within a draft range that is a bit on the higher side of what most stoves require. And it is in fact a narrower range, as well, since that range starts closer to the upper limit of what would be acceptable for most stoves. Too low, and the secondary is more apt to stall... too high, and the stove is more likely to overfire.

Trouble is, this downdraft technology tends toward the overfire range in a "normal and "good" hot burn. I have seen the back of my stove in the 800F range, even with primary air shut, as the draft pulls in more secondary air than I would personally offer, if I had any ability to manually control the secondary input (other than stuffing foil in the holes).

Good to know. When I ran it without a damper, It ate wood faster than anything and I got very little heat out of it. It would also stall unless it had a very deep coal bed. I suspect the rush of air somehow cooled it down or that air was getting pulled in somewhere where it wasn't supposed to.

 

[Boiler74]

This is probably a stupid question, but what do you do with the two test holes when not measuring draft? Cap them some way? I know that air should be drawn in, but that's not ideal as it can cool the flow of air up the chimney. I have a manometer and would be interested to know my draft number. And I know I could put a couple barbed taps on the flue, but capping them was my quandary.

 

[jdonna]

I think you guys are pretty on par with most in the range of .06" to .10" for draft. Seems like .08" is the magic number. I have a manometer installed on my stack due to the high winds and tall stack on my big stack. I use it to tune the turn key damper but rarely needed on the fireview anymore after switching to a better chimney cap.

I did try a baro as an experiment, but was unhappy with the amount of air that was drawn in and the increase in soot in the black pipe. Others will suggest on here the chance of a chimney fire and the possibility of the baro flap swinging wide open feeding the stack unlimited air to the chimney fire.

 

[Hardrockmaple]

This is probably a stupid question, but what do you do with the two test holes when not measuring draft? Cap them some way? I know that air should be drawn in, but that's not ideal as it can cool the flow of air up the chimney. I have a manometer and would be interested to know my draft number. And I know I could put a couple barbed taps on the flue, but capping them was my quandary.

Sheet metal screws.

 

[jbythesea]

This is probably a stupid question, but what do you do with the two test holes when not measuring draft? Cap them some way? I know that air should be drawn in, but that's not ideal as it can cool the flow of air up the chimney. I have a manometer and would be interested to know my draft number. And I know I could put a couple barbed taps on the flue, but capping them was my quandary.

The hole is so small that you can probably ignore it. Like Hardrock said, you can stick screws in them. If you have one, an internal temp gauge would make double duty of the hole.

 

[begreen]

I use it to tune the turn key damper but rarely needed on the fireview anymore after switching to a better chimney cap.

What chimney cap did you switch to?

 

[jdonna]

I saved the box, it was on a close out rack at Menards. I will post again when I dig out the box, long story short, I have a smoother, more even draft and can turn the air down a lot lower without worry of whoofing or back puffing. I confirmed it with the manometer, not such wild wind related draft surges that I used to have. (.08"-.26")

 

[DTrain]

If you have the magnehelic tool you can measure it. They sell on eBay.
(broken link removed to http://www.ebay.com/itm/Dwyer-Magnehelic-2001-Gage-Pressure-Gauge-Water-Level-Meter-0-1-00-w-Case-EXC-/141134222840?pt=LH_DefaultDomain_0&hash=item20dc4155f8)

I like data.