Draft setting for most efficient heat

Highbeam.. I am sure your BK is a beautiful option.. king came in close 2nd on my choices.. I do not know what my temp is at cap.. it's 27 plus feet up.. but I cleaned my chimney this year.. less than 2 cups.. mostly light brown not crunchy.. then before dark today.. 1.25 cord since cleaning.. I popped cap and looked half cup of fly ash looking on bOttom cover it's clean . so it's whatever I'm doing is working ..

I would be interested in Brian input as he is an efficiency guru on his stoveand setup BDF ..

 

Well, potential fire prevention (too low and you get creosote forming) and wood savings (you'll be able to dial in the highest stove temp related to lowest flue temp). I would think this would be your ideal range. Totally in line with Highbeam's train of thought.

 

If I don't regulate my draughts, I usually fall asleep and the stove goes out.

 

Must have been years ago. At this point I must rely on the instruments. The Condar meters haven't let me down yet. I recall the feeling that very high flue temperature readings weren't accurate but since getting rid of the hearthstone I haven't seen high flue temps.

 

Yep, it was a number of years ago. Time heals all wounds, or something like that.

 

Makes me want to puke thinking about it, spent about 3 grand on a stove that drove me crazy, high flue temps and low stove top temps make for a headache, bought a 700 Drolet and works like a charm.

 

Today I received the new stovetop gauge I ordered. The flue gauge will be in next week.

I have a low-medium burn going right now, STT about 485 with the infrared. The STT indicates as shown below:


(Ignore the rusty look, the stove is new, I took the photo in dark conditions and enhanced it so it was readable, and that is what I got.)

The gauge doesn't have numbers, just ranges. I chose that intentionally; when I want a number, I will point the infrared at it. The outer ring of the guage is for STT, so it is indicating a little less than mid-scale in the target zone. At first glance that looks reasonable, it is not a huge/hot fire, the draft is half closed, and it is burning clean.

When I have the chance I will try to establish what the top end and bottom end temps are for the target zone. I missed it coming up, as I was at the dinner table. And it is too warm in the house to bump it to the top end.

 

Simple; it lets you know how hot or cold the flue is so that you don't have to worry about creosote buildup and a chimney fire.

 

I'm curious about this as well but pretty sure the efficiency goes up the lower you can run. Assuming you're not burning below the minimum burn rate for complete combustion, which will vary with each stove and tube vs cat, etc. So it's basically a heat exchanger question right, and if someone knows the formulas better I'd like to know. The heat exchanger is fixed - your stove, so the main variables are temperature differential and dwell time. The lower you burn and the slower the exhaust passes through the stove and pipes the longer it is in contact with the heat exchanger. Now on the other hand a higher rate of burn increased the temperature differential which increases transfer, but I think it is offset by the contact time being to short, and more heat is carried away.

 

Well, to add to the fire here... I have my NC-30 stove cranking for the 3rd year here now. It has an OAK. Got it in a deal from HD for cheap delivered from VA though a post on Hearth before I and others were banned over there. Things I have learned burning this and other stoves and boilers several have posted about above, but I will post them here:

One is that if you open the draft too much you will overfire pretty much any stove or boiler in a hurry. The NC-30 is no different. I run it at most with the draft open between 1/8th and 1/2 an inch. I leave the door open a crack to start until the wood burns nice and hot and the secondaries kick in, and then I seal the door and ease the damper in more to slow the flame and just until the secondaries start to sputter, and I leave it there. If the house is cold I will run the stove hotter with the secondaries cranking more and run the fan on the stove as well as a box fan at the side (which is always running) to put more heat into the house faster. That burns wood faster though. Once the house is up to temp, I lower the damper to 1/8 an inch open and let the stove run at a lower temp. Then I feed it at a steady rate, keeping it half full at most, unless it is below 20F outside or really windy, when I start to fill the beast 3/4 full.

In all stoves and boilers I have run, a smaller fire burning hotter is always more efficient. If you always stuff stoves and boilers full, you wind up making charcoal, and that is a waste of energy. So I usually burn 2 or 3 medium size splits after starting with more smaller splits half filling the stove and keeping it half full (unless it is really cold or windy). I ran my OWB the same way, as well as my earlier Earth Stove here that the NC-30 replaced.

One thing about these EPA stoves is that they are designed to pass EPA tests, and not designed to run at best efficiency the way that most people run them. And most people run them dirty, damped down to the max so that they create a lot of smoke and creosote. In reality, this is the way that you will usually get the most heat out of them for the longest time though. I found that out pretty fast with this stove. I get more heat for longer in my house if I damp it down to 1/8 an inch overnight... but the window blacks up and the flue gets more creosote that way. So I try to set the damper out a tad more which seems to be the best compromise. Again, it depends on the temp outside. If it is in the 40s, 2-3 splits will keep the house warm with the damper almost all the way in (1/8th an inch out). In the 30s, I need more heat and add more wood, and set the damper out maybe 1/4 an inch. In the 20s I start to crank the stove up hotter and feed it a lot more wood. My rule of thumb is 30 degrees will require 2x the wood as 40 degrees. And 20 degrees will require 3-4x the wood as 40 degrees. Wind also greatly affects heat loss and heat needed. When I cannot keep the house warm enough with medium density woods, I reach for my stash of oak and locust hardwoods. Otherwise I burn mainly softwoods and lighter hardwoods like lodgepole pine, Doug fir, cedar, hemlock, bigleaf maple, and larch. Wood type affects burning as well, and old growth and knotwood will burn hotter and longer than younger growth and straight wood will. Dry wood will burn better than wet wood as well. Most of my wood is 15-20% moisture, and dried for at least 2 season here before I burn it.

Many variables affect the wood type that I burn, the damper setting, and the amount of wood that I keep in the stove. Generally it comes down to outdoor and indoor temp, and wind. Also an advantage of burning softwoods is that they generate far less ash, so it is easier to burn them and not have to clean out the ashes all the time.

 

Dex, you are my F'ing hero! That air wash plate on yours has melted and sagged. Mine did too! I'm not alone! Mine happened when I was watching it, under 700 but the key was that I was warming it up at full throttle. I now only use full throttle as little as possible.

I run the NC30 hard. 700 as long as possible with an upgraded blower and deck but I always see that sagged baffle as a failure. I'm happy to have company.

I did my best to straighten it out but it is still sagged. Does your airwash still work okay?

 

My brother got a 100# bag of anthracite coal one year when we were living in California. We were at a friend's who insisted on trying to burn the coal in his wood burning stove. So we tossed in a few rocks with some wood splits and overnight they melted through the wood grate in the firebox. If there were no firebricks on the floor of that stove it would have melted through the bottom plate of steel!

Coals from hardwoods also get really freaki'n hot. I have to remind myself when I flip to hardwoods here in cold spells like we are having here now (13F here last night) that I have to change my wood burning practices. Maple tends to spark a lot and results in a lot of ash, and the coals last forever in the ash. Those coals radiate an enormous amount of heat when you stir the ashes, like I did this morning. Yeowsah! That is not Doug fir in there, dude! One reason that conifers do not coal up like hardwood is that they create little ash, so they burn off faster. Conifer wood and resulting coals are also a lot less dense than hardwoods and store less energy per unit volume, so they are not as radiant hot when exposed to air.

 

That's getting into "a soft glow" territory when the lights are turned out...