Increase ventilation for wet wood??

[LauraLL]

Hello! I have recently moved to a place heated with an ATMOS DC 30 GD Wood Gasification Boiler. My partner and I are almost totally new to wood burning and are really feeling our inexperience here... After weeks of struggles and being unsure of whether our issues (a lot of tar and soot being produced) were down to issues with the boiler (before we fired up, it was serviced and the guy was surprised the previous owners had kept it running, as it obviously hadn't been cleaned in a loooong time), or to our wood being too wet, or a mixture.

The wood has been drying outside for 1.5 years and cut about a month ago (kicking ourselves for not doing that as soon as we moved in 3 months ago). We bought a moisture meter and while some of our smaller pieces are down to the recommended 15%, we're probably at an average of 20%. The chimney sweep has since been by and confirmed that this is the cause of our problems - he also said he's been coming to this boiler for 15 years and (politely) said he has never seen it in such a state.... We're feeling very foolish and although we suspected that, we didn't want to believe it.... Because here is the issue.
This is the only wood we have. The price of dry wood is astronomical right now. We can get a little bit from family who are no longer burning wood and have a leftover stack, but we really can't afford to buy much. So we're intending to mix this dry wood with our 'wet' wood to hopefully ease the effect. BUT. Is there some way we can also 'hack' the boiler to provide more air? I ask, since we are using the same wood in our indoor wood stove, which presumably?? has a greater airflow indicated by the tiny fraction of soot production compared to the furnace.
Is it a very very bad idea to tamper with the draught regulator e.g artificially prop open the air regulating flap? Any other suggestions? Are we totally screwed?
Thanks in advance from a slightly desperate person!

 

[Tonty]

First off, how do you check the moisture on your wood? The correct method is to split a piece and test it on the freshly split surface. You do not get an accurate reading testing on the end of a piece, or on a piece that is not freshly split.
I’m guessing your moisture is above 20%. It shouldn’t cause too many issues at 20% or below, I wouldn’t think. I don’t know that boiler, so I’m not sure if there is anything you can do. More air would therotically make a cleaner burn, but I don’t think I’d recommend it in practice. There’s just not a lot you can safely do with a gasifier boiler when you have wet wood.
You may just have to try to heat the best you can with your stove this winter. Stoves are more forgiving with wet wood than a gasifier boiler.
I’m sure you’ll get some more advice here. Good luck, and stay warm.

 

[Ashful]

The wood has been drying outside for 1.5 years and cut about a month ago...

The unfortunate reality is that your wood has been drying for about a month. Wood doesn't dry much at all in 1.5 years in log form. But you didn't mention the wood species, as the drying behavior can vary quite a bit by species (by more than 3:1 or 4:1 on time).

Tonty already gave good advice on how to measure MC%. It must be on a freshly split face, and at some reasonable temperature (eg. 10° to 30°C). Best practice is to grab one split each from three different places in your stack, bring them indoors for a few hours, then split and test three places on the freshly-exposed face. Then average these several numbers to get an average for your stacked supply.

You're on a good path with trying to get some dry wood to mix with the wet. Some like to get pallet wood or compressed sawdust manufactured logs, for this purpose.

If you want to dry some wood fast, the two ways most often used are:

1. solar kiln. Maybe not too practical approaching December in Denmark, but we have members in Alaska who use this method, with excellent results. @Poindexter has his variant, and @Woodsplitter67 has another. Check them both out.

2. Move some wood indoors, near the stove. This is not preferred, due to mold, bugs, everything else. But if managed sensibly, can help a little. Mind your minimum safety clearances, and stack such that it cannot fall onto / near stove.

 

[LauraLL]

Thanks for the responses!

@Tonty Yes we are measuring on freshly cut pieces. The larger ones are significantly more than 20%, but we have avoided using those since we bought the meter. It is a cheap one though so I suppose it could be that it isn't properly calibrated.
Yes, I think we'll have to heavily on the stove!

@Ashful Oops forgot to write that. It is spruce. Very unfortunate! We bought it from the same estate that we rent our house from - they knew what we needed it for and gave us the impression it would be fine. Little did we know.
Everything burnable including sawdust blocks etc are outrageously expensive, but I'll look out for a deal. Thanks for the drying tips. Solar kiln could be good in the future, but you're quite right, we're not getting much sunlight these days in DK! And yes already moving wood inside (with the considerations you mention).

Until it has dried out some more/we get some drier things to mix in though, should we avoid using the furnace at all? So far we're lucky that the weather has been very mild...

 

[Ashful]

Just remember, your 20% target MC is averaged for a load, by weight. Worst case, framing lumber is 8%, and some quick and dirty math will tell you the by-weight ratio to mix that with your existing wood supply, to get near 20% average per load. Not the cheapest solution on earth, but possibly still cheaper than alternatives.

I have a friend in Germany who was updating me on energy costs there, about a month ago. I assume the situation is similar in Denmark? Our energy is so cheap by comparison, it's really tough for Americans to even relate to the situation you are in, especially recently.

 

[EbS-P]

You are going to have do do the math and see what is the cheapest path. I did have some success by bringing wood inside and using a dehumidifier to blow dry air over through and around a stack of wood. I would try to find space for 2 cubic meters of wood inside. The more air that can circulate around the wood the better. The dehumidifier doesn’t need to run all the time but have a small fan would be good. My guess is that it would take 60-70 kWh a month to operate. It will generate some heat too!

Burning wet wood is just frustrating. Maybe mixing in some bio/sawdust bricks will help. 1 brick per load?

 

[sloeffle]

I ran a PSG Caddy wood furnace for 12 years that would fall on its face if the wood was >20% moisture so I'm very familiar with your sitaution. I keep my wood in totes and one year the squirrels decided to make the insides of my totes home and tore all of the plastic wrap off the top. As others have stated I brought wood into the basement to dry out and I mixed some bio-bricks in with my loads.

I looked for a manual for your boiler online but couldn't find one. If your boiler uses a o2 sensor you could up the % of oxygen. I would also see if there's a setting to open the dampers more. The manual for my OWB gives your various setting based off of the moisture of the wood. The setting for higher moisture wood have the three settings I talked about at higher amounts vs wood with lower moisture.

 

[salecker]

go scrounging for pallets or framing lumber scraps
Do you have a company the builds roof trusses in your town.They will have lots of scraps of milled wood which you could mix in each load.
Company's building houses have waste to get rid of,Maybe a section in your dump for wood.I know that there is enough dry wood tossed into the dump in my town to heat a home.

 

[Tonty]

I would do some experimenting, especially with fuel prices tbe way they are. Try scrounge up some really dry wood, as mentioned, and mix it in, taking note of a mixture that works well to be used in the future.
It could be your boiler has some settings built in that you could change, as mentioned earlier, that would allow wetter wood. That should be safe.
If you feel comfortable with finagling the boiler controls/dampers a little, go ahead, but do it very carefully.

 

[Poindexter]

I cannot endorse modifying your boiler to increase airflow.

I think your best option is going to be to muddle through this winter somehow, and have your spruce wood fuel for winter of 23/24 split, stacked and top covered by mid March of 2023. Spruce will dry quickly, if you can stack it up off the ground a few inches (maybe 200mm or more) and cover it on top to keep the rain off. Spruce split stacked and top covered in March will (should) be ready to burn in October of the same year.

For muddling through, mixing kiln dried wood (like construction scraps) with the damp cord wood you have is probably the way to go this year. There was some discussion here among mostly Yanks and Canadians about what Europe could do this year with natural gas supply being what it is, back in April and May 2022. Besides having softwoods like spruce, pine and fir split and stacked a couple months ago, the other good ideas were to buy another blanket and find someone to share your bed, get a dog to share your bed, look at air leaks in each house, and look at upgrading insulation.

The importance of sealing air leaks cannot be overstated. No matter how thick your insulation is, if you have big air leaks you are wasting money trying to heat the back garden instead of keeping the heat in the home. It doesn't matter what fuel you are using for heat, air leaks are bad. Can you get some kind of plastic that will shrink down around your window frames when you apply a hairdryer?

We have been waiting for you to stop by. Outside of renting airBNB within Ukraine that I am not taking my wife to this year, I am glad to help and will go back to read this thread a little more closely. I imagine your climate is a bit more severe than the UK since you aren't benefiting from the Gulf Stream ocean current and probably pretty similar to Helsinki.

 

[Poindexter]

Ok. So for Copenhagen you got worry about plumbing pipes freezing in Dec, Jan and Feb. For Helisinki, add Nov, March and April.

My first strategy would be to accumulate all the dry wood scraps you can lay hands on, but save them for the times when your temperatures will be below freezing so your water pipes don't freeze. You will need to cocktail, or mix, your dry scraps with your damp cordwood so each load in the gasification boiler is 'dry enough' during freezing weather.

Your small splits are under 20% and work good in your indoor wood stove, so you are not screwed. You are inconvenienced.

Your top four priorities I see, from post #1:

1. Bring in 8-10 cubic meters of green freshly felled still juicy and sticky spruce/ pine/ fir (about 4-5 north american cords) right way, and get those split, stacked and top covered before March 2023. Sooner is better. You don't need to build passive solar kilns, just get it split and etcetera right away. That will save you from going through this again next winter.

2. Accumulate all the dry wood (no paint, no glue) that you can get your hands on for when you need to run the boiler in below freezing weather to keep your water pipes from freezing.

3. Go find your air leaks - usually windows and doors - and get them plugged.

4. Resplit your big moist splits to smaller pieces and bring them indoors as best you can.

I am not the only Alaskan who reads international news. Right now all of Europe is my brother from a different mother, or, as required, my sister from a different mister.

 

[Poindexter]

regarding post 4, you do not need an expensive tool to measure the moisture content of cordwood. Something in the US$30 to US$50 range is perfectly adequate. The US$400 meters are for the folks about to build heirloom furniture from tropical hardwoods than have been seasoning in a climate controlled space for 10 years.

Split open a split, put your pins in parallel to the grain on the freshly exposed face with the wood at or near room temperature and you are close enough for rock and roll.

@Ashful and I hardly ever disagree about anything that actually matters. Logs don't season, they don't dry out, but they do rot. Birch is probably the worst for this. Birch I like to split at least once the day I drop the tree to minimize rot. Spruce is a LOT more forgiving on rot, but spruce, at least the White and Black spruce ( Picea glauca and Picea mariana) that grow in Alaska, don't really start to season or dry out until they are split at least once. I burn spruce exclusively at my home and split round logs at least once down to 3-4 inches ( 90-120mm) in diameter so they dry better. Under 3" diameter (~90mm diamter) but cut to stove length my local spruces will season in one summer.

You probably can season birch down to <20%MC in one summer without a kiln. If your birch splits are less than about 120x120mm, split, stacked off the ground and covered on top by mid March 2023 they should be ready to go in October 2023 at 15-18%MC. The bark will start falling off your birch splits when they get down to 12-14%MC, don't look for that in one summer without a kiln.

A splash of peppermint schnapps in a mug of hot chocolate at bedtime can be quite lovely and warming.

If you can get hold of any shipping pallets, the current hand saws (Made in China) where the induction hardened teeth each have three facets work pretty good even though they are disposable. These would run US$8-15 at home stores, just pick the one with the most comfortable handle. If you can find some pallets, just leave the nails in, cut the wood down to size and beware the nails in your ash bucket - unless your boiler has a catalytic combustor in it with a coating of noble metals like platinum or palladium.

If your stove (or boiler) has a catalytic combustor in it you will want to cut the nails out of the pallets and beware of nails in the ash bed of your outdoor firepit.

 

[Poindexter]

@LauraLL , I will try to keep an eye on this thread, but I do have to go back to work tomorrow after 15 days off. Everyone on this site is encouraged to tag me back to this thread if there is anything I might have to offer.

 

[maple1]

Don't mod your boiler.

Re. your existing wood. Resplit it small, stack inside somewhere in your boiler room (don't know how much room you have) and set up a box fan blowing air on it. ASAP. The dry indoor air movement should make it more burnable as the weeks go by. That won't be immediate. But it will pay off in a month or 2.

 

[LauraLL]

Wow this place is great. So glad I found this site! Really appreciate all of your advice. I'll see what I can scrounge and move as much as I can inside - will look into a dehumidifier too. I'll also split our larger pieces again. I won't go messing with the boiler.
We haven't properly moved in as we have been renovating, but this week we can finally move into the part of the house with the wood stove so we can be less reliant on the furnace for a while. Maybe even until we need to worry about pipes freezing. Which with the warmest October and November (so far) in a couple of hundred years, could well be later than usual.

@sloeffle no option to adjust O2 unfortunately. We can adjust a pin for secondary air, which is currently on the setting for our wood type. It is my understanding that it is a bit difficult to adjust properly without a way to measure O2? Just in case you are interested, I have attached the manual. No pressure to read it of course!

@Ashful yeah it's pretty tragic. We're actually just very lucky that we're set up for heating with wood here - if we can manage to figure this out and find some cheap dry stuff, our heating bill will be pretty low this year considering the crisis. The prices of electricity/gas have gone up by insane amounts (electricity around 300% over the last year). The demand for alternatives has ballooned (firewood by comparison has gone up by 100-150% in the last 2 years) and the wait time to order a furnace/wood stove for instance is now minimum 8-14 months. When we moved in we bought 18m3 of wood to process ourselves for 6000,- DKK. Naturally cut and dry is much more expensive, but 1.8m3 of cut, dry wood is around the same price as our big stack... if you can even find it! Sawdust pellets and such are not much cheaper.

@Poindexter Wow really appreciate the detail here and you looking in to regional considerations. We have already ordered our supply hopefully for the next couple of years. This time a mix of spruce and beech. It is being felled soon, so that's really helpful to have an idea of the timeframe we should be looking at.
It's an old drafty house and we already have plenty to do to get comfy before winter really hits - we'll be blocking up some gaps, but blankets it is.... And we'll stock up on snaps!
Good to know about the logs, we could see in our stack that the ones in the bottom weren't doing great... The ones we moved home we raised up on pallets. We didn't cut some of the smallest logs (diameter < 15cm), but I will be doing that now. Hope you had a good first day back at work!

Thanks again all!

 

[sloeffle]

@sloeffle no option to adjust O2 unfortunately. We can adjust a pin for secondary air, which is currently on the setting for our wood type. It is my understanding that it is a bit difficult to adjust properly without a way to measure O2? Just in case you are interested, I have attached the manual. No pressure to read it of course!

I see where they talk about o2 in the manual but I don't' see how the boiler is measuring o2, and the boiler doesn't seem to be a lambda type boiler or have an o2 sensor.

Section 25 - I don't see the issue with adjusting the primary and secondary air. They give you the parameters to stay within. It might be possible the current parameters are incorrect. Have you checked them ? Do you have a manometer measuring your draught, and an temperature gauge on your chimney ?

Section 26 - Wood moisture: 12 - 15 % recommended. I have never seen non-kiln dried wood get to that moisture level. Wood is hydroscopic, moisture content is going to vary based off the season and climate. When I built custom furniture we were happy to see <11% moisture for kiln dried wood during the summer.

 

[Ashful]

will look into a dehumidifier too.

If you're placing that wood in the same space as a heat source, I suspect you may not really need a dehumidifier. Heated spaces (esp. drafty ones) are always going to be too dry in winter, so any moisture that wood is releasing may be to your benefit.

Of course, if this is a basement or other place that doesn't tend toward "too dry", then you may still need dehumidification.

 

[LauraLL]

@sloeffle No, exactly. It isn't the best manual, but it was my understanding that it would be an external sensor?
We have adjusted the primary and secondary air to the max recommended setting for both for softwood. It isn't very clear to me in the manual, but I'm assuming that pulling the pin further out increases the airflow.
There is no/we don't have a manometer or temperature gauge :/
Hmm regarding those %s. Elsewhere in the manual it says 12-20% (Section 6 and a Note in the beginning).

 

[Ashful]

You can make your own manometer for less than $10. All you need is some clear tubing, liquid, and a ruler. You're probably trying to measure with ~0.5mm water column accuracy, so water itself isn't going to work too well, you won't be able to see it accurately enough on a ruler. Get some liquid lighter than water (eg alcohol, meriam red oil, veggie oil, etc.), bend a length of clear plastic tubing in a "U" shape, tape it to a ruler, and you have a manometer more accurate than any magnehelic. Put some food coloring in the liquid if it helps with visibility, and be sure to weigh a known volume so that you can scale it to water (which is 1 g/cc).

Chimney probe thermometers are cheap here, likely in Denmark as well. The most common model here is the Condar FlueGard, which used to sell for about $13, although I just Googled it, and now I'm seeing prices $40+!

 

[maple1]

If you're placing that wood in the same space as a heat source, I suspect you may not really need a dehumidifier. Heated spaces (esp. drafty ones) are always going to be too dry in winter, so any moisture that wood is releasing may be to your benefit.

Of course, if this is a basement or other place that doesn't tend toward "too dry", then you may still need dehumidification.

This. Forget a dehumidifier. Get a box fan. Way cheaper to run and likely just as effective.

 

[Poindexter]

18 cubic meters? That is awesome. After you get your existing large moist splits smaller and are bringing those in to dry further before their night of passion, your next priority is to get your 18 cubic meters of logs cut to stove length and split once. Just leave the halves on the ground in a pretty whopping pile.

American Beech is Fagus grandifolia, European Beech is Fagus silvatica. I have never handled silvatica. grandifolia is going to take two years to season for burning. I last dropped a grandifolia I think in 2007 or maybe 2008. I was hoping to make furniture out of it. I was spraying latex paint on the freshly cut faces as I cut it to length, one at a time, and then splitting to halves after the paint dried, and then covering my 6-8 foot half logs under trees branches with the leaves still on the branches to keep the sun off them, and the whole tree ended up getting burnt in my stove. I expect your silvatica is goign to twist and bow a fair bit in the stacks as it dries out. You will probably have to restack it 3-4 times over the summer of 23 and summer of 24, but it should burn really really nice in September 2024.

Get your green wood split once, then split all the Spruce-Pine-Fir down to stove size and stacked off the ground and top covered. Then go back to the half logs of beech and get those split to roughly 120x120mm and get that stacked off the ground and top covered. Your goal is to get all the cutting to length and splitting and stacking done my March 17, 2023. You won't make it, that is about 9 cords of wood. Also, if you can find pallets it is probably prudent to cut them up to burn this winter and stack your new incoming splits directly on the ground.

Short version anyway, I will be back tomorrow, long before you are done cutting 18 m3 of logs to stove length and split once.

 

[EbS-P]

This. Forget a dehumidifier. Get a box fan. Way cheaper to run and likely just as effective.

If you fill up an entire room with wet wood and are wanting the fastest drying time the dehumidifier will help greatly. It doesn’t need to run the whole time. But keeping the RH below 60% is a good idea.

 

[sloeffle]

@sloeffle No, exactly. It isn't the best manual, but it was my understanding that it would be an external sensor?
We have adjusted the primary and secondary air to the max recommended setting for both for softwood. It isn't very clear to me in the manual, but I'm assuming that pulling the pin further out increases the airflow.
There is no/we don't have a manometer or temperature gauge :/
Hmm regarding those %s. Elsewhere in the manual it says 12-20% (Section 6 and a Note in the beginning).

I don't see anything in the manual about a o2 sensor, just talk about the correct % of o2.

Of the two items I suggested the thermometer is probably the most important. When you start running things as wide open as possible there are ramifications, and one of those could be a fire that burns too hot. Yes, that can even happen with wet wood, been there done that. Not sure if these are available in Europe but a wi-fi type thermostat such as a Inkbird or Fireboard would best IMHO. You can setup alerts on your phone for them. The idea is, the thermometer would let you know if your exhaust temps are getting high. Ideally you want to stay around 300 - 400F ( 150 - 200C via google ).

Section 10 - Do you have a "throttle valve". That's an interesting name. dang Brits. In the U.S. we call that a barometric damper. Does your boiler have that setup ? A manometer would be used to verify that the "throttle valve" is set correctly. If the "throttle valve" that is set too far open would cause your boiler to not draft enough. That would be something I would want to check also. You would want the manometer to measure the draft between the boiler and the "throttle valve".

 

[Poindexter]

@LauraLL , I put your problems in the back of my mind today while I was working.

1. 18 cubic meters is closer to 10 cords than it is to nine cords. Most likely 18 m3 of logs will meet your heating needs for 2 years, with a maybe half of your third winter's supply ready to go. I say this because the temperatures of Copenhagen and Helsinki are roughly similar to the northern half of the USA, and most wood burners in the north half of the lower 48 burn ~about~ 4 cords per year. The trick is we don't know how good your insulation is, we don't know how well your air leaks are sealed, and we don't know how warm you intend to keep your home.

2. If you can get wooden pallets, plan to chop them up or saw them up and use them with your moist cordwood, some of each every time you load the boiler.

3. If you can get some plastic shipping pallets, take them. You can use those to elevate your incoming wet cordwood off the ground, and you can keep the plastic out of the waste stream likely for decades. What I have found is dry cordwood laying in the grass, just dropped on the ground, will absorb water out of the dirt. To get the wood dry again I have to do something to decouple, something to detach, something to separate, the wood I am trying to keep dry from the water in the underlying dirt.

Worst case you can stack the wood you have directly on the ground, knowing the bottom layer or two will not be dry enough to burn anytime soon. Second, you could lay a sheet of plastic on the ground and stack your wood on that; but you would want to trim the plastic fairly close so your drying wood isn't laying in a puddle of rain water with a plastic bottom. Best would be getting the wood pile 4-12 inches off the ground, 10-30 cm above the dirt.

4. If you can get everything cut to stove length, every thing split once (into semicircular halves), then go back through the pile and split the spruce to stove size and get all the split spruce stacked off the ground and top covered before the middle of March 2023 you will do fine next winter, but after you take a couple days away from the wood pile to celebrate the rites of spring you really need to keep going and get all that beech split and stacked ASAP, before June 1, 2023 will probably be OK.

5. If anyone offers you any spruce-pine-fir (SPF), accept it. I am not suggesting you drive to Rome Italy for a quarter of a cubic meter of spruce, that would be foolish; but pretty much all the trees in the SPF group will be ready to burn after seasoning one full summer if you can get them split and stacked by April first or so.

6. What I am seeing online is it pretty much rains in Denmark year round, you are going to need to cover your wood piles on top. It doesn't matter if you use metal or plastic or anything else, you are going to have to be vigilant about keeping rain off the wood you are trying to dry. Dripping or blown water droplets on the sides of your stacks are usually OK in most situations, the main thing (in most areas) is to protect the top. You will know by mid June or so if you can get away with just covering on top or if you need to cover at least the upwind or windward side to keep the blowing raindrops off.

7. How much land, how big an area do you have, to season your 18 cubic meters on after you cut the logs down to size?

 

[LauraLL]

Ok, I am horribly frustrated right now. Sorry for the long message, but here's where we are at.
Yesterday had a full day resplitting large pieces, moving smaller splits into the furnace room (it's pretty big) and splitting whole logs. I was a bit more systematic about measuring splits: freshly cut, parallel to the grain, an average from several places in the split, of around 10 pieces of similar size.
I found that our smallest pieces - which we have almost exclusively been burning with for last couple of weeks - were actually pretty consistently from 14-16%. Larger pieces which we were avoiding (which I have now halved) are average 19%+/-2-3%. Freshly cut logs were surprisingly not so different; small around 17%, large at about 25%. My partner is even insisting that these values are artificially high as he thinks the meter isn't calibrated properly (based on comparisons with wooden furniture and values we got from a previous meter that broke). I can't believe in that though!
The temperature has also suddenly dropped 10 degrees - perfect timing for me deciding to take a break from using the furnace huh! So we fired up about 3 hours ago* - and I honestly just don't understand what is going on. The kettle is refusing to climb higher than 40 °C. Opening up the hopper, the fire seems to be burning really low as it 'wakes up' when we open the door. We have just given the whole furnace (tubes, flue, everything) a thorough scrubbing - there is still creosote that I can't get off, but much less then we have had before. Primary and secondary air are on max recommended values.
We have previously had one semi successful period of about a week, using these small, apparently dry enough, pieces where we were consistently getting the kettle up to the recommended temperatures, but so much tar/creosote/soot and condensate was being produced. As in when I opened the lower section to clean behind the furnace every 2 to 3 days, liquid came gushing out each time... Ours is in an outhouse so the mess isn't an issue, but I know that you are supposed to be able to have these in a home, so something is clearly going very wrong?
Doesn't it sound like something is up with the air supply/draft?? Why though I have no idea. We know that the previous people living here had this darn thing working. I don't know what we're doing wrong! @Ashful thanks for the tips for making a manometer. It would be great to have these pieces of kit and thermometer etc @sloeffle so that I could actually 'see' what is going on. Feels like we just adjusting things blind which doesn't feel good. I'll look into it.
@sloeffle Thanks so much for looking at the manual btw. And yes that's what I meant, that the set up itself has no O2 sensor. I'm one of those dang Brits haha. We do like a strange technical term, it is true. Nope, there isn't a throttle valve. It seems to be a very basic set up? We also know that our tank is too small for the system - so previously when we have had it up to temperature, we have been half filling the hopper - otherwise the fire gets smouldered when the kettle heat has no where to go.

I'm thinking we need to get a pro in to take us back to step 0 because I feel totally lost and so very confused at this point!

*firing up - from small pieces of wood to make a good layer of glowing coals (in Danish they are literally called 'glows' (gløder) which I think is quite nice). Then filling up the hopper.