Why Are Draft Specs Not Listed By All Manufacturers?

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.

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.

BurnIt13 said:

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.

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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.

branchburner said:

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).

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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 said:

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.

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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.