My personal nightmare with wood!

[begreen]

It's hard to compare numbers. Blaze King is one of the few companies that has tested their stoves for HHV efficiency. I'm not sure how that it equates to Woodstock's EPA (LHV?) efficiency, but the 40,000btus need to be multiplied times the efficiency percent for real numbers. A guess would be 75%. or 30KBTUs per hour. I think BK tests their stoves with Doug Fir for cordwood, but it would be better to ask BKVP that question.

 

[rideau]

8600 BTU's per pound x 72% efficiency= 6200 BTU's. I believe that, when burning dry wood, the heat lost to combusting water reduces the usable heat to 5000 BTU's per hour. I believe burning wet wood reduces usable BTU output to more like 3000 BTU per hour. That's from memory, but I'm not about to look it up at this hour.

The basic point is that it is very easy to load over 1 1/2 cubic feet of dense hardwood into the (I stand corrected) 2.2 cu ft fireview, which at about 40-45 pounds per cubic foot equates to 60 - 67.5 pounds, and IN FACT, the stove produces a lot of heat when burned in an 8 hour cycle, very even heat, with significant coals left in a stove that is still at cat temp after the 8 hours.

 

[begreen]

Without a doubt it produces a lot of heat. So does the larger capacity 30NC run pedal to the metal. The question is, is this enough to meet the heat loss of the house?

 

[Michael6268]

I am leaning to think the wood is not right. The OP states to burn about 6 cords of oak/maple mix from October to early February. Wood tested to have 12% moisture. First, getting wood in NH to 12% even with 3 years of seasoning would be an accomplishment. I have 3 year seasoned ash and maple but never got below 15%. (Sure not a big difference and the MM could be just a little off but on the other hand it's not oak either.) 6 cords of that wood would also be almost twice as many BTUs than he burned in coal before suggesting it is not just bad house insulation. I would like to see a picture of a split of that oak on a scale. 1 cu ft of dry oak should be ~45 lb. Maybe it was not oak, maybe part of it has become punky, but no one can tell me they burn 3 cu ft of dry oak down to few coals in 4 hours without the stove melting away or the flue showing more than 200 F. The energy has to go somewhere or it was not there to begin with.

im sure mm is accurate. Wood is stored in old ventilated greenhouse. but for conversation sake lets say its wetter than 12 %. Are you saying drier wood would last longer? I think not. Maybe hotter but not longer. My big complaint is the length of time, not the btus. When burning it heated pretty good. 600 stove temps etc. The problem was after a few hours the fire would die out and need refueling. I tried 2 bunbles of supermarket wood for the fun of it and lasted a max of 45 mins near 600 fully dampered.

 

[Grisu]

im sure mm is accurate. Wood is stored in old ventilated greenhouse. but for conversation sake lets say its wetter than 12 %. Are you saying drier wood would last longer? I think not. Maybe hotter but not longer. My big complaint is the length of time, not the btus. When burning it heated pretty good. 600 stove temps etc. The problem was after a few hours the fire would die out and need refueling. I tried 2 bunbles of supermarket wood for the fun of it and lasted a max of 45 mins near 600 fully dampered.

Oak is notoriously slow to dry and getting it to 12% in our NE climate would be surprising. Thus, I was wondering whether you have really oak or some faster drying species. However, what you describe is more like a solar kiln, so 12% in 3 years is a possibility.

One problem in figuring out what is going on with your stove are the bits and pieces of info that you are supplying. Maybe you are just overestimating burn times but it is hard to figure out. Let me describe one of my typical burns:

From a cold stove, I will start a small fire with some softwood, kindling and newspaper. I leave the air about 1/4 open. Stove will get to ~500F. After an hour, fire will be mostly down to hot coals, stove temp maybe ~400 F. I rake the coals forward and add as much dry hardwood as I can only leaving maybe 1" gap to the baffle. I wait until the wood has caught fire, then close the door. Stepwise I will close the air down over the next 15 to 20 min. Flames will shift from the wood to the top; very strong secondaries, usually looking like little gas burners. Stove will reach peak temp in the 700 F to 750 F range about 1 hour after reloading. At that time wood will have settled a bit but still fill most of the firebox. Over the next 3 hours, few flames in the wood, lots of flames in the top. After about 3.5 hours, secondaries will be mostly down to a few flare-ups. Maybe a little flame from the wood. Wood down to orange/white coals, will fill about 1/3 of firebox. Stovetemp still 500 F to 550 F but starts dropping now. After 6 hours, few hot coals left, stovetemp 350 F to 400 F; time for reload, rinse, repeat.

That is with mixed hardwood. When I burn pine then you can cut those times in half, which makes me think you don't have oak there. I doubt you could even burn 3 cu ft of oak in an open fireplace in less than 1 hour. In addition, 3 cu ft of oak are at least 400,000 BTU. Burn that over 8 hours and you still have 50,0000 BTU/hour. Should be plenty for your needs.

I don't have a flue thermometer but temps on a single wall should be in the 600 F to 700 F range after the reload and over 400 F when the stove is dampered down. 200 F to 300 F would be a recipe for creosote.

 

[TradEddie]

Are you saying drier wood would last longer? I think not. Maybe hotter but not longer.

He might not have been, but I will say exactly that, and doubly so for oak. There must be hundreds of threads on this site explaining the many reasons dry wood is so much better. It's not just the energy lost to boil the water, but dry wood can be burned at lower air settings, wasting less heat up the flue, allows more air to the secondary burn tubes, and my own pet theory that water suppresses the reactions that generate the gases key to good secondary burns.

In an ideal world, burning dry oak with the air set properly, you should have strong secondary flames, usually purple, with little or no flame in the wood itself, just a hot glow underneath to drive smoke and gases to the secondary tubes. This should last for 3+ hours depending on stove and load size, and even when those secondary flames are gone, with oak you should have many more hours of strong heat but little flame as the coals burn down too. In the coaling stage, if it's especially cold, I draw the coals to the front air supply and open the air to get the heat out of the coals faster. For me, the coaling stage is almost as much useful heat as the secondary burning.

Maple, OTOH, is a shoulder season wood for me, short fires, no lasting heat. Maybe you have much less oak in that mix? Can you tell them apart?

TE

 

[Highbeam]

I don't have a flue thermometer but temps on a single wall should be in the 600 F to 700 F range after the reload and over 400 F when the stove is dampered down. 200 F to 300 F would be a recipe for creosote.

I must disagree. The surface temps of single wall correspond with double the internal temps. Chimney materials are only rated to 1000 degrees so a 500 degree surface temp on single wall connector pipe is the "redline". My single wall flue spends a lot of time in the 300-400 range when the stove top temp is in the 600-700 range.

 

[Highbeam]

That seems like a bit of an overstatement for the 2 cu ft Fireview. There are only so many btus one can get out of a 2 cu ft stove in 8-10 hrs. One can never pack the stove fully (no air gaps) and if the stove is say 75% efficient, the math just doesn't seem to prove out. For sure the stove will not be putting out the same btus at hour one that it will at hour 8. Blaze King has lab tested their stoves for output over time. The King has 88% LHV Efficiency (82% HHV) and has a tested result of 51,582 BTU's/h constant output for 12 hours. Kind of hard to see a stove half that size and much lower efficiency achieving similar results, but maybe it's magic. Not knocking them, they are a great company, but let's be realistic with the numbers. For sure visit them and consider the Ideal Steel as an efficient alternative.

This and those that own that fireview and have actually measured have found that woodstock's measuring stick is broken. Woodstock does not make a large stove, they make medium, small, and very small. Comparing anything from their line to a king is apples to oranges.

I own and operate a BK and the NC30 and can easily burn through a full load in 6 hours with the NC30. There are still coals for a relight but the definition of "burn time" is a major factor here. The visible flames go away and coals are held in the belly for a long time.

The OP bought a smaller output stove than he had and with way lower burn times so it is taking more effort for less heat, a recipe for a perceived disaster. The available coal stoves are just so much bigger. It is too bad that there are not more high output wood stoves available.

Like going from a big V8 engine to a 4 banger in the same truck. Often you get similar mpg but the 4 banger is agonizingly slower on the hills.

 

[Ashful]

I must disagree... My single wall flue spends a lot of time in the 300-400 range when the stove top temp is in the 600-700 range.

Ditto. My single-wall runs 250'ish most of the time, in the early part of the burn cycle. Lower toward the end of the burn. No creosote here... the cat eats it all, and farts clean gas.

 

[Highbeam]

Ditto. My single-wall runs 250'ish most of the time, in the early part of the burn cycle. Lower toward the end of the burn. No creosote here... the cat eats it all, and farts clean gas.

Cat stoves are a different animal since they are not designed to flow such a huge amount of air all the time as Mike from ESW pointed out so well. The cat stove in my experience runs a MUCH cooler flue temp for any given output level.

The non-cats send a lot of heat up the flue, so much that you can easily overfire your chimney system.

 

[Michael6268]

600 to 700 degs on single wall pipe??? And you get long burn times That must be after the stove melts and your framing catches fire! Dont quote me but I would think that would=1200+ internal temps. Even if only for a short time that would devour my wood.

 

[begreen]

Highbeam had unusually high stack temps with his last stove. Not sure why. They are not the general case. I don't usually see over 6-800F peak temps with a probe thermometer unless I space out turning down the stove. Once I have turned down the stove they track about 100F lower than the stove top temp until the coal stage.

 

[bluedogz]

My chimney is 24'. Splits were approx 3-4 inches on average
I am wondering if I am expecting too much. How long do you guys actually have flames in the stove before it goes to coals? Seems I only could keep flames for a couple of hours, then went into coaling stage and at that point it wasnt even close to

I have exactly the same stove, almost the same square footage house, and approx. the same chimney.

Last winter (2012), burning 2-year CSS cherry and hickory, I could hold 500 stovetop with my eyes shut, and keep it for 4-5 hours. Temp measured with a magnetic therm at center of stovetop step. Oh, and using pretty big splits- 5-6" on top of coals.

This past winter, I got the same as I finished off that supply of wood, but then got progressively worse results as I started working my way into less-and-less seasoned stacks. By February, I was burning cherry that has sat in rounds for 2 years, but had only been split for maybe 6 months- winter just would not quit and it was that or break up the furniture.

By the end of February, my not-quite-seasoned cherry would only offer an hour or two of flames, and maybe another hour or two of coals, then nada. I stretched it out by adding Envi-blocks, but that's another thread.

Solely based on this, my $0.02 is that there's something we all don't know about the wood. Michael6268, have we checked more splits with the MM? From 4-6 diff places in the stack? And on fresh-split faces? (I know, that's first-grade-level input, but we'll start there...)

 

[Highbeam]

Highbeam had unusually high stack temps with his last stove. Not sure why. They are not the general case. .

Hearthstones are notorious for extra high flue temps but it is very normal for flue temps on a non-cat to track the stove top temps once everything is up to temp. When trying to heat up a non-cat, with high draft settings, it is normal for flue temps to near the 1000 degree internal temp redline.

So I would disagree, I do believe that it is the general case that a non-cat stove can be run such that the flue temps are too high before the stove top temps reach normal limits.

 

[begreen]

Every setup is unique. IIRC BrowningBar reported lower flue temps than you were seeing with his Hearthstone.

Steel stoves warm up a lot faster than stone stoves. I watched temps closely with this mornings fire. Half load of wood, fir and madrona mix. The flue temp never got over 750 and that was very brief. At the 10 minute mark secondary combustion had kicked in, though stove top temp was still low. At the 15 min. mark I was turning down the air half way. Flue temps started to drop as the stove top started coming up. By 25 minutes I had the air most of the way closed. Flue temps continued to drop as the stove top rose in temp to an eventual 590F with flue temps around 500.

FWIW, the Castine was slightly better with lower flue temps, perhaps because I had it hooked up rear vent and the T6 is straight up?

 

[Kosmik]

Ok sorry my mistake. Splits are definitely not the problem. Guess my estimate was way off. Looked st a ruler today and realized they were at least 6-8 inches. Smaller ones packed on top. Usually up to the burn tubes.

Overfiring will eat wood quick. Perhaps shutting it down earlier is called for. I found I was waiting until 'charred' to turn down, and that was eating my wood up quick, and sending me to overfire land. Started learning when I could start turning air down to get the secondaries going, otherwise flames be going too fast to see it working and by the time stovetop thermo read 450-500 it was too late for me, reading lag.

Perhaps an OAK and some sealing/insulation will get the losses right.

Funny problem you have, haha, everyone coming from electric/propane is always amazed at how much heat is coming out...Not the coal crowd.

 

[Seasoned Oak]

I can get 8 hours with pine in my 30, so im sure i could get much more with oak.

 

[Kosmik]

Just for chitsngiggles next time you run it, put the stovetop where people are suggesting...Then give us the breakdown of the stovetop/flue temps. Probably just running her hotter than 600.
And the more heat running up the flue, the more cold air being brought into the house for the stove.

 

[Michael6268]

8 hrs of what? 8hrs of usable heat in sub zero temps or a couple hrs of usable heat and enough coals for relight?

 

[Michael6268]

Just for chitsngiggles next time you run it, put the stovetop where people are suggesting...Then give us the breakdown of the stovetop/flue temps. Probably just running her hotter than 600.
And the more heat running up the flue, the more cold air being brought into the house for the stove.

Will do! Unfortunately you probably havent heard the last of this issue or probably this thread. LOL

 

[Kosmik]

Where were you before with the coal, using three tons 75M btu? Not the same house/location?
The cycle of the fire is generally less output in the coaling stage. Once the secondaries stop firing the heat output goes down, IME. So if it needs to be secondary firing heat output all the time to keep house warm, you need a bigger stove or better insulation/sealing.
Get that roof to R-60 (or close as you can), you're in a cold enough place.
Check those doors/windows for leaks. Heavy cloth blinds or rigid styrofoam inserts can really help with leaky windows at night, I ended up taping plastic around mine this winter. I could see the air leaks really easy then.
Is basement or floor insulated, or is heat being leaked into the surrounding environment.
Make sure that attic hatch is well sealed. Big losses there, straight shot to freedom.
Did the house feel 'drafty' this winter.

There are also methods of preheating the incoming air to the house, trick is house has to be well sealed so you can bring in air at particular spots.

 

[begreen]

8 hrs of what? 8hrs of usable heat in sub zero temps or a couple hrs of usable heat and enough coals for relight?

Required heat and usable heat are not the same. Yesterday our stovetop was still at 400F 8 hrs after starting the fire. It was plenty warm to keep our house toasty. This was on a half load of wood. In other words, plenty of usable heat. But outside it was around 46F. Your issue is not with usable heat, it's just that the stove is unable to meet your required heat without you stoking it like a locomotive. This is because the house's heat loss when it is very cold is near the stove's normal heating capacity. Reduce the heat loss and the stove might easily heat the house for 8 hrs between loads. That is our normal reload cycle at 15F outside with roughly the same sized stove and house. It the temps dropped to below zero (and I hope they never do here) then we would probably be in the same boat because we have an old farmhouse with too much glass area.

 

[Kosmik]

Seasoned Oak, post got misplaced I think.

DId you happen to get a reading of the flue pipe temp on the stove. Id be interested to know what that would be . I have a hot air coal stoker with the flue pipe coming out the bottom and on low fire its darn near room temp. Not losing much heat up the flue on that one.

 

[Grisu]

I must disagree. The surface temps of single wall correspond with double the internal temps. Chimney materials are only rated to 1000 degrees so a 500 degree surface temp on single wall connector pipe is the "redline". My single wall flue spends a lot of time in the 300-400 range when the stove top temp is in the 600-700 range.

You are right. I messed up internal and external temps. My apologies.

 

[Grisu]

600 to 700 degs on single wall pipe??? And you get long burn times That must be after the stove melts and your framing catches fire! Dont quote me but I would think that would=1200+ internal temps. Even if only for a short time that would devour my wood.

I am sorry that I messed up internal and external flue temps but is that really the only comment you have to my post? You are claiming to burn through 400,000 BTU worth of wood in 4 hours and are concerned about me overfiring my stove and flue? You know we are really trying to help you here but as I said it is hard when info are not forthcoming and it somehow feels like not everything is being told. Like that:

8 hrs of what? 8hrs of usable heat in sub zero temps or a couple hrs of usable heat and enough coals for relight?

There was no mentioning before that the NC30 is struggling to heat your home when the outside temps are subzero but instead it sounded like you always have trouble heating with it. Of course, you are asking a lot from a 3 cu ft stove in that scenario. I would side with BeGreen then that the stove is undersized for your heat loss. Maybe keep running the coal burner when the temps are in single digits and below and use the NC30 for anything above that.