@begreen , what US stove(s) can you think of with a peak output around 17k btu/hr, epa cert non cat with a reasonably sophisticated secondary burn chamber? I have given up on trying to find the firebox size for the Broseley Evo5 multifuel. I am gonna guess pretty close to the Englander NC13, maybe a touch bigger but significantly smaller than the NC30. The OP paid $1838 for his...80.5% efficient burning wood.
@Hesslemount , I love puzzles like this. Really. I could be in the garage banging on my toes with a torque wrench right now, but figuring this out is intriguing.
My personal (catalytic) stove, this one: (broken link removed to https://www.blazeking.com/EN/wood-ashford30.html) , when I turn it down to low will do 3.75 kw for 30 hours straight on one load of cordwood. It will run at 11.2 kw when I need it to. Clearly a much bigger stove than you need.
According to gov.uk, here: (broken link removed to https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/497436/Application_Pack_Ricardo_EE_Issue_v4_Final.pdf) (page 5) my stove would have to emit 8.7 grams per hour, or less, to be certified in the UK. On the US test cycle my stove came in at a tenth of that.
But you are a demographic of one within the UK that we know of here. We usually get one or two new members from the UK annually, You have unusually dry wood, and a lot of it, compared to our limited experience with UK burners. We do have some Ozzies that keep the place active in the American summer actually.
The application fee for an appliance exemption if you wanted to import something similar but smaller is GBP 1695, about USD2300. Plus shipping from North America, plus VAT. Even if you are in your early 20s, it probably makes economic sense for you to learn to deal with ecocoal, because your break even point on all that up front to get a state of the art wood stove would be decades. You would still be working as a tree surgeon 40 years form now, and processing 15-20 cubic meters of cordwood annually the whole time, to break even compared to figuring out how to burn eco-coal in the stove you have.
The good news is I am an expert BBQ cooker and know a thing or two about burning charcoal chunks ;-)
I don't think you have a draft issue. This is confirmed by your 14% cord wood burning down hot and fast, but a modern good quality insulated chimney liner, given a high fire, should measure 12-16 Pascals easy measured at the stove collar, 10cm up, 20 cm up, 70cm up from the collar. You didn't mention the flue height in your original post, but if you have the recommended 5 meters (16'4") you are golden on draft, have nothing to worry about.
The CO emissions of eco-coal relative to cord wood, page 5 of your burner's manual,
http://www.broseleyfires.com/uploads/files/guides/Evo5 Multifuel Issue 1 21-07-2015.pdf
are pretty impressive. I think the "at 13% O2" means the exhaust gas contains 13% oxygen, so your stove is only consuming about 1/3 of the oxygen that comes through the air intake. That should be, given the sophistication of the secondary burn system, a pretty clean burning stove with good efficiency, and indeed the specifications bear this out. For a non-catalytic stove you have a good unit with good efficiency and pretty good emissions, but it won't run overnight on cordwood, as you already know.
My guess is your usable firebox space is something like 2.0 to 2.2 cubic feet, something like 55-60 liters.
Getting a good consistent burn out of charcoal is all about chunk size. For an all night burn you are looking to load up 2.0cubic feet, 50 odd liters of charcoal, and looking for a consistent 8-12 hour burn. Probably a bit of inconsistency you won't notice while you are sleeping, the tipping point would be if your burn is inconsistent enough that you wake up cold and have to open the door of the stove to poke at the coal bed and go back to bed. This is an expert level charcoal burn in the US.
Pork shoulder will put up with a lot of swing in the average temp during a 10 hour cook and come out really good. A 12 hour charcoal burn with minimal temperature swing is for beef brisket. For this you need to be from Texas, or a BBQ fanatic, or apparently any old homeowner in the UK.
Chunk size. Any pieces of ecocoal you got that measure 3cm max, by like 1cm minimum with the third dimension falling in between are chavel. Gravel sized charcoal. Chavel is useless for cooking brisket. The pieces lay together too tight for good airflow, they don't burn good, they don't burn hot, save the chavel for pork shoulder or sprinkle chavel on regular sized, already lit coals when slow cooking meatloaf.
I can't believe I am giving away brisket cooking knowledge on the internet for any old schmo to find by accident, but here you go. You want all your chunks between golf ball sized and fist sized, say 3cm to 10cm in diameter. I truly have a sieve for this, but I am kinda fanatical about my brisket cooks.
What I would probably do, if I win a Rhodes scholarship tomorrow or etc.. first thing home from work I would stuff that burner with cord wood and burn it down. Getting close to bed time I would load up eco-coal 3-10cm pieces on the hot wood coals, let that get started real good and then turn it down right before bed. In the morning, I would stuff it with cord wood again, let it run while I was doing my morning routine and turn it down as I was leaving home for the day.
If you save your eco-coal pieces under 3cm to use on your BBQ cooker will they mess up the taste of your food?
You are probably looking at starting with a cold burner every afternoon when you get home from your work day, but with cord wood at 14% this won't be a huge challenge. Could it be that 9:10 burns you had a bunch of chavel in your eco-coal bags?
Sucks that a state of the art stove is probably not economical for you. Really. I have been on this site for a number of years now and you are the first burner from the home islands I can think of who probably really could use a catalytic stove as it was designed to be used without having to make drastic changes in your daily routine.
Best wishes.
