Efficiency Tradeoffs of burning w/ max primary air

[Highbeam]

My experience has been the same as cClydeburner and Begreen. Once established my air is turned down to closed or nearly closed for most burns. If I require more heat I'll bump the air open a bit more but temps would skyrocket if I ran wide open. I let my stove get a little to hot on a reload last night and it took hours and hours to come down from 750 stove top to 500 with the air right closed. Also before I 'remembered' actually smelled that I'd left the air wide open to long I was reading 660 exterior single wall stove pipe about 12"s above stove collar(digital auberins) and at about 18"s up my condor magnetic thermometer was nearly buried. So I had flue temps heading into the danger zone but my stove top was still in the 700-800 range. Wasting fuel and creating a potentially dangerous situation.

Yes, most folks aren't trying to get high output from their non-cats as the title of this thread inquires. When you want the 700-800 range you need to use a high throttle setting but not so high that you overtemp the flue. When you only want that nice 500 degree efficient cruise temp then you can use low throttle settings.

 

[begreen]

Remember most folks here are burning hardwood. Burning locust I can close the air down completely and have a 750F stove top with 650F flue temp if I want. If I tweak it open a little bit the stove top would be 800F. That's plenty hot enough. I'm not trying to find the limits of the stove nor the limits of the flue system.

 

[Clydeburner]

With a modern non-cat you can only run hot or hotter. There is no low temperature option as can be shown when you all get full 500-600 temps with the air closed.

I would agree that non cats love to be in the 500°-600° range for the best burn (firebox temps close to 1100° to burn the smoke) and the only "low" burn we have is a small, still hot, fire.
I would rather cruise at 500° or 600° for a prolonged time, getting a few less initial btus, then blazing the house down for an extra 100° stove top. So it takes an extra 20 mins to heat up, I'm good with this

 

[Highbeam]

Remember most folks here are burning hardwood. Burning locust I can close the air down completely and have a 750F stove top with 650F flue temp. if I tweak it open a little bit the stove top would be 800F. That's plenty hot enough. I am not trying to find the limits of the stove nor the limits of the flue system.

Those are some low flue temps. Internal temps right? Corresponds to an also low 325 on the surface with a 750 stove which would be very efficient. The normal burn range for the surface of the flue is 275-475 as I recall. When running my non-cat hot, on purpose, as this thread is about, I watch both thermometers. If either approaches the red zone then I back off the throttle. Very intuitive but also very different than somebody trying to run a non-cat cooler and with high efficiency.

My redline for stove top temps is well below 800! I don't want to melt this thing. I am also burning straight hardwood now but not as many btu per lb as locust.

Probably more than most posters on this forum I actually run my non-cat at 700+ on purpose whenever it is running. I know what it takes to keep a non-cat stove hot hot and low air is not it. For those that don't know I intermittently heat my 1800SF shop with 14 foot ceilings by running the NC30 hard with an aftermarket blower and convection deck. The goal is to raise this space and all the contents from 50-70 quickly so yes, I am the posterchild of this thread.

 

[begreen]

Yes, internal temps are all I report here. We haven't had a single wall flue since '05 with the F3CB.

But... if you want to dump heat into your home quickly do you get the same efficiency (total BTUs given off), albeit shorter burn duration, from the same load of wood if you run primary air 100% open?

The OP started off the thread asking about opening the air 100% for more heat. That wouldn't work for our stoves. Max heat, depending on the wood burned, would be with the air somewhere around 25% open. More than that is just going to heat the flue up to a dangerous temperature.

 

[Blowndiffuser]

This could be due to different emissions standards. Where does one find the emissions for UK stove models? I'm curious about how they are tested and what the testing results for emissions are. In Dovre and Stovax stove literature I am only finding %CO listed.

Emissions are tested against BS 3841 and PD 6434 for DEFRA approval stoves. Unfortunately the standard is not free but I've found a few sites with a little info on them.

https://www.bsria.co.uk/services/test/product-testing/solid-fuel-stoves/
http://www.hetas.co.uk/professionals/standards/

And yes most of our stoves are multi-fuel (including both of mine), but I think the only real difference between a multi-fuel and a dedicated woodburning stove is the addition of a grate to ensure free flowing air under the coal. I just make sure that have a good inch or two of compressed ash from the previous burns to create a good base for the next burn and keep the grate covered.

 

[begreen]

Thanks!

 

[Ash]

With a modern non-cat you can only run hot or hotter. There is no low temperature option as can be shown when you all get full 500-600 temps with the air closed.

That's bogus.
It's a fairly nice day here so I lit a smaller fire about 4 hours ago that peaked at 450 degrees and the stove is at about 390 now. Perhaps you need some lessons on how to burn in a non cat or need to get a different stove if all you can burn is hot or hotter.

 

[Squisher]

The way I burn at lower temps in my non-cat stove is to just build smaller fires. Of course I'll never see the extended burn times of a cat stove, I don't expect to. But just building a smaller fire and doing smaller reloads seems to keep things more reasonable in warmer times. Big loads to get the extended burn times out of my non-cat will generally see my stove cruise between 400-600 stove top, with it falling off near the end. It works well for my house.

 

[Highbeam]

That's bogus.
It's a fairly nice day here so I lit a smaller fire about 4 hours ago that peaked at 450 degrees and the stove is at about 390 now. Perhaps you need some lessons on how to burn in a non cat or need to get a different stove if all you can burn is hot or hotter.

Load that thing full and try it again. Bogus. Sheesh.

If you only light a match and throw it into an empty stove then I suppose you think you just burned a room temperature fire too?

 

[Squisher]

Ash I believe he meant in comparison to a cat stove. Which I would accept. From reading on here seems cat technology would be the way to go if burning low and slow quite often.

I burn hot and heavy most of the time hearing my entire home from one stove in the basement so my non-cat works well for me.

 

[Ash]

Fully loaded my stove burns nice and hot no doubt. I burn like that whenever it's cold and it heats a house built in 1904 in northern Minnesota just fine. However I can build smaller fires on nice days and my non cat cruises along just fine at lower temperatures. I don't get the extended burn times of a cat stove but I don't expect to either. For highbeam to say that a non cat stove can only be ran at hot and hotter temps is ridiculous. I burn smaller fires in the shoulder season also to heat up the stove and the cast iron will hold that heat most of the day when its mild out.

 

[Squisher]

But to burn cooler in a non-cat you really have to watch that you're not running to cool and gumming up your flue. I believe in a cat stove that's a non-issue. I think it was Begreen that I saw post something recommending shorter hot fires in a non-cat vs just burning cooler(my apologies if it wasn't him that posted that but I've read that on here somewhere).

 

[Ash]

But to burn cooler in a non-cat you really have to watch that you're not running to cool and gumming up your flue. I believe in a cat stove that's a non-issue. I think it was Begreen that I saw post something recommending shorter hot fires in a non-cat vs just burning cooler(my apologies if it wasn't him that posted that but I've read that on here somewhere).

Agreed. A smoldering fire is no good for sure but you don't need to have a raging fire all the time either to keep the chimney clean. I burn dry hardwoods and clean my chimney every spring and most years it barely needs it.

 

[Squisher]

For sure, I find it quite easy to control my house temperature compared with the 25+? Year old stove it replaced. I just thought it was worth mentioning that burning cooler with a non-cat takes some vigilance to ensure you're not fouling the chimney. Obviously like you've states an experienced burner can do it with no issue.

 

[Ash]

Good advice squisher.

 

[begreen]

But to burn cooler in a non-cat you really have to watch that you're not running to cool and gumming up your flue. I believe in a cat stove that's a non-issue. I think it was Begreen that I saw post something recommending shorter hot fires in a non-cat vs just burning cooler(my apologies if it wasn't him that posted that but I've read that on here somewhere).

I find that in the T6 a partial load (maybe 2/3ds) that is turned down pretty quickly will peak somewhere between 500-600F and burn for about 6-8 hrs. In the Castine I was able to shoot for 400-500F and get it. However, even though I ran it at a lower temp, the Castine was highly radiant and caused a greater room temp swings than we see with the T6. This year I have been loading it full up to about 48F outside with no room overheating. That has lead to delightful 12hr loadings. A lot of this is just me continuing to get educated. Since retiring I have had a lot more time to dial in and learn to run this stove at its best. Subtle things and timing can make a difference.

 

[Squisher]

Heck yah there are endless subtleties. That is one of the things I'm finding fascinating about this new stove now is trying to figure out how to get it to burn more and more efficiently. I feel I'm still very much in the learning stage with it and still end up failing miserably the odd time. But every now and then I really nail a load and am just amazed at how long of a burn with really good heat I'm able to achieve.

 

[Ash]

However, even though I ran it at a lower temp, the Castine was highly radiant and caused a greater room temp swings than we see with the T6.

I find the same to be true with my IR. Even with a smaller fire it can keep throwing out heat and can really make it quite warm in the house

 

[7acres]

A lot of this is just me continuing to get educated.

Wood stove subject matter that begreen doesn't already know? Mind. Blown.

 

[begreen]

Learning new stuff is half the fun of stove ownership and being here.