Help getting higher evaporation rate

[gatzow]

I bought my first wood burning evaporator this year. Moved away from propane turkey fryers. This is what I bought.

http://www.rothsugarbush.com/product/wood-evaporator-the-classic/

Advertised as 10-15 gallons per hour burn rate. I used it for my first time yesterday and averaged about 7 gallons per hour once I got it up, hot and boiling. I thought early on that I simply had too much sap in the pan, but as it dropped to an inch or two, the evaporation rate didn't really change. Still was around 7.5 gallons.

I am only in my 3rd year at this, I am still learning lots. Anyone have any ideas as to how I get closer to that 10 gallons per hour mark? That 2.5 gallons per hour means a lot to me base on the 60 taps that I have this year.

Thanks for thoughts.

[psparr]

Dry wood cut to wrist size and fire every 6-7 mins. Keep the air vents wide open and fire it hard and you should be ok.

[RileySugarbush]

Does it have a grate? It's critical that combustion air comes in low and goes up through the fuel.

If it is one big firebox, that is a limitation as well. About half way back the firebox should end and the exhaust moved up and concentrated to flow right under the rest of the pan.

[Woodsrover]

....but as it dropped to an inch or two, the evaporation rate didn't really change.....

How much sap are you running in the pan? I try to keep mine not much more than 1/2" deep.

Small, dry wood added often.

[psparr]

Your a brave man woodsrover. I run down to a 1/4" or less when I shut down to drain the evaporator but it's 3/4" for me.

[littleTapper]

Looking at the bricking instructions, there's no ash pan/grate and no ramp. Looks like you could build a brick ramp in it to help a bit. Add some kind of cast iron grate if you can and find a way to get more air in. Otherwise, you're probably getting about as good as you can get with that design.

[gatzow]

Thanks all. Ill start by splitting wood smaller. More work, but if it helps get it hot, great. I was also thinking of adding a grate, if nothing else to get the wood higher to start. It took a long time to get enough heat in that giant box to get a solid boil.

Summary of all - smaller wood, think about air flow, get as hot as possible... Keep liquid low. That means that I really need to build a drip system as well. I do not have that yet....

[psparr]

Probably your biggest issue is no grate. I would keep the sap at at an inch till you get used to it.

[RileySugarbush]

I agree 100%. You don't want a campfire on a breeze day, you want a forge! Easiest thing to do, go get a cast iron fireplace grate and throw some bricks behind it so the air has to go up through. A welded grate will soften and collapse. That will be a huge improvement.

For a second step, put anything in to build a shelf and force the flow up and along the bottom of the pan behind the grate. It doesn't need to be a slope. Half pints are bricked that way. I don't know what they were thinking with that bricking instruction. It doesnt need to be perfect. You can even sacrifice some concrete blocks. They will be destroyed by the end of the season, but they will work for now.

Third step. Add even the smallest of blowers on your air inlet ( under the grate) and stand back and watch the steam! Prove it to yourself with a little hair dryer on air only, or a shop vac output. (not permanent, just a convincer!)

If you do all three steps, you can probably double your rate.

And don't go below 1" this season. Next season, don't do it either.


Probably your biggest issue is no grate. I would keep the sap at at an inch till you get used to it.

[Ghs57]

The biggest thing that helped my ghp rate was probably adding air under fire/air over fire (AUF/AOF). Much hotter fire, even if you can only do air under fire (under a grate of course).

Second biggest thing was timing my firing. You don't want to see any diminution in the boil rate. For me, it's every 6 1/2 minutes. If you don't have a timer, and have a smartphone, download a free interval timer or equivalent app. You must be regular with the wood size and firing. I didn't think this mattered so much until I started doing it. Good dry wood can make a huge difference also.

These, and tweaking your evap as mentioned above, should help.

[O3C]

I agree with Riley sugarbush, I had 3 different friends stop in yesterday and they all said the exact same thing, This thing is like a forge ! Ron

[gatzow]

Thanks for all the advice. I will be starting a fire tomorrow. I got a grate that fits perfectly in the evaporator. I re-split wood and have the splitter next to the shack to keep working tomorrow. My Menards was out of firebrick, so I am put a couple cement blocks in for a wall and will get firebricks to replace. I'm ok with ruining a couple of cement blocks....

Looking forward to seeing how this changes things tomorrow. I am burning mostly dead elm trees, which I am hoping will burn hot. I'll probably keep the pan at 1.5 inches until I really get experienced with it since this is only my second boil.

Appreciate all the help.

[Ranger_Andy]

The Triangle of Fire is your answer, Fuel, Oxygen and Heat... Address the 1st 2 to get your boil rate up. Dry hard wood, we split ours palm size...small firings, crisscross your wood to create more air and burn area and force some air in somehow...

If you really want an instant idea on whats happening in the fire box, add a chimney thermometer...You will get almost instant feedback to anything you do...We use an Auber http://www.auberins.com/index.php?main_page=product_info&products_id=292 ...The Auber will give you nearly instant feedback...We use to fire by time, but we set up the Auber and do it by temperature now...every load of wood is slightly different and the stack temp tells us exactly what is going on. With the alarms set up, you can walk away and do other things...We have it set up so that when the stack temp drops to a certain temp, its time to fire...

[maple flats]

It can also help to add another length of stack, even if it is 24 ga. galvanized. The extra height can help create more draft and that makes it boil harder. Give it lots of air and wrist size wood and you will be fine.

[gatzow]

Boiled today with the modifications suggested. The first 4 or 5 hours were awesome. Boil came very quick, and I started at about 10 gallons per hour. Then the problem came when I started to accumulate coals that took over the grate and started to build up over time. Are you guys constantly shoveling hot coals out to keep room for airflow? I did not today, and I could tell that as it continued to build up, I went from 10 gallons per hour down to about 5 or 6 at the end. Without cleaning it out, I think it would fill up within about 12-15 hours - like the whole thing to the point you cannot add wood....

Thoughts?? I am burning mostly Elm if it matters.

[Sugarbush Ridge]

Boiled today with the modifications suggested. The first 4 or 5 hours were awesome. Boil came very quick, and I started at about 10 gallons per hour. Then the problem came when I started to accumulate coals that took over the grate and started to build up over time. Are you guys constantly shoveling hot coals out to keep room for airflow? I did not today, and I could tell that as it continued to build up, I went from 10 gallons per hour down to about 5 or 6 at the end. Without cleaning it out, I think it would fill up within about 12-15 hours - like the whole thing to the point you cannot add wood....

Thoughts?? I am burning mostly Elm if it matters.

gatzow,,,,, somehow you need to get more air under your grates, blower, or get a rod,bar and poke open grates for more air to come up I used to fire on the ground and as you say a mound of coals. My first AUF I done with a pipe in the bottom of pipe and end sticking out a couple feet from fire. Flatten the end,,,, I took a side grinder and cut slots in pipe. Actually my first blower I used the house vacuum and taped the discharge hose to the pipe. Any kind of a blower,,, Fire burned like a blacksmith forge and boiled over in less than a minute. I'm single so I didn't have to worry about some lady of the house saying I couldn't do that

[Super Sapper]

You are adding too much wood too fast. You need to let it burn down a little farther before adding more or add less each time.

[RileySugarbush]

I saw that too when on a block arch. Key is to get as much air as you can up through the grates and stop other air as best you can. Plugging leaks in the blocks and adding a panel to stop air flowing in and over the fire. This is one of the toughest parts of a block arch. You need what is essentially a steel arch front and door for loading wood.

Or stop and shovel out coals. Or get a blower, but even that won't work completely if you have too much air flowing over the top.

Here is the sad/happy truth: You will get tired of fighting this and end up with a true arch! Just a matter of time!

[gatzow]

Just wanted to say thanks to all that replied to this thread. Boiled again today and all the improvements made have been great. Still need to think about a blower, but I used a lot less wood today and kept a solid boil while not piling up coals inside the box. Big improvement for a longer boil.

I'm certain that I will be asking for more ideas - next up is a drip system or warmer as I am losing too much time slowly putting cold sap into the pan. If anyone has pics of their drip systems, id love to see them at gatzowc@hotmail.com I'll also be searching this site for ideas.

Appreciate the help.

Chris

[billyinvt]

As I recall, elm makes for pretty poor firewood unless it is exceptionally dry. It might be a good idea to start looking for sawmill slab scraps to mix in there. Check craigslist. Sometimes they're giving them away.

[Bill@mysticmaple]

Get some air blowing in under the grates. I have an arch that I welded from two oil drums under a 2x5 Smokey Lake Hybrid, could not get a consistent boil rate thru the day, started out fine but as the ash built up we fought with too much heat in the box in the form of coals. Once I put a small blower under the grates, the ash does not build up! At the end of the day the fire box is as clean as the start.


2017; 100 taps on gravity, 20 on buckets, home built RO
2016; 60 taps on gravity, 2x5 Smokey Lake Hybrid
2015; 35 taps on buckets, 2 16"x20" flat pans

[RollinsOrchards]

We use a mix of half hardwood and half softwood to keep the coals from building up too much. Forced air under the grates makes a big difference in keeping the coals burning.

[Helicopter Seeds]

I was having same issue of coal build up on my brick arch, and note that the coals smouldered for two days so I was concerned about burning after shutdown. I dropped about an inch at night after the boiling and steam had stopped. So I just ordered a vogelzang grate that is designed for a barrel stove, and I will put it on top of a row of bricks. got it online from northern tool. This will make a higher amount of air space below the grate so longer before ash clog, plus the peak fire will be closer to the pan.
On the other hand, slower boiling in the evening gives more time to relax and pace yourself. When I am tired at 9 or 10 PM, an hour of slow steady boil may be better than 45 minutes of frenzy, busy busy busy fire tending.

[stoweski]

Love that blower! Went from a 50 cfm on a 2x6 up to a 274 cfm this year. I was worried about ashes spewing out of the seams in the ash door on the front. No issues so far. Just a roaring boil in the flue pan. Well worth the time and small investment!