Reasonable/Acceptable GPH boil rate on a 2 x 5.5 with a steam hood?

[Old County Road]

This past weekend I was finally able to fire up my used Lapierre/Waterloo/Small 2' x 5.5' evaporator. The back pan is 2' x 4' and is a drop flue design. The front pan is 1.5' deep by 2'. The stack is 10" and runs up through the roof with a total height of probably 15'. The evaporator has a 2' x 6' steam hood with a 10" stack that also has a total height of probably 15'. I have a squirrel cage blower installed under the arch doors.

I boiled this past weekend for 23 hours total and averaged about 13gph which seems low to me but wanted to check with others on that. My wood is a mix of split up hemlock slab wood that is mostly dry and fist size hardwood that is very dry.

I expected to be boiling in the upper 20s low 30s vs the low teens. Any thoughts on what I shoud be getting for gph evaporation?

Thanks!

[fisheatingbagel]

I have a Smoky Lake 2x5 hybrid, also a 5" drop flue design. I average 25 gph with small dry wood. I have a blower, but it's too small to make much difference. No hood or preheater. I have an 8" stack. I think you should be able to get 30 gph with a blower.

How does the boil look in the flue pan? It should be boiling "vigorously". What is your sap level in the flue pan? How often are you firing?

I wonder about your Hemlock that is "mostly" dry. Have you tried boiling with just the dry hardwood?

[Mead Maple]

I borrowed a neighbors 2x4 divided mason flat pan last year. With my 275 oil barrel arch and a blower I could cook that at 13gph but never a drop more


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[Old County Road]

Hey Dave - the boil in the back pan was pretty vigorous but I don't have much to compare it to as this was my first boil on the rig. I will try your suggestion of just burning hardwood for a coupe hours and see if that makes a difference. I am pretty sure the previous owner told me he could get low to mid thirties out of the rig.

In terms of firing times I was trying different times between 10 and 20 plus minutes. I found that if I kept the firing times closer to 10 minutes the front pan wasn't boiling well as it cooled off quickly when I opened the doors to load wood. When I went 20 minutes or so the front pan boiled much better but the back pan died off toward the end.

I ordered a stack thermometer so I am going to keep an eye on that and see if I can find the sweet spot on when to fire.

[maple flats]

When I use some hemlock (I have a sawmill) slab wood my boil rate drops a little. You say the hemlock is "mostly dry", that might be part of the issue too. I would think you should be able to get over 20 gph, maybe 25, not likely 30 unless the wood is dry, and split "wrist size" not fist size. Also, if the hemlock still has the bark on, surprisingly that can slow it some too. Hemlock like most evergreens actually have a natural fire retardent in the bark, to help them survive a forest fire.

[gbeneke]

Your evaporator has about 30 maybe 35 square foot of surface with those flues. With the steam hood and stack heights you should be getting at least twice your rates or better. Use your hard wood and keep it stoked more often. Your pants should get hot after 15 seconds when the door is open.

[Old County Road]

Thanks Paul - I used to boil on a 2 x 4 flat pan for years and usually averaged 10 gph - so only getting 13 gph on the 2 x 5.5 is a bummer. I am going to tweak a few things and hopefully make a better showing. I am assuming the hood helps - but I was also wondering if in some ways it could hurt. The steam seemed to be pretty good though when it was going.

[Old County Road]

Thanks for the input and advice Dave K and Wood Loader. I did not know that evergreens bark has a natural fire resistance - good to know! My slab wood (from my Wood Mizer) was really dry - but then got snowed on in an early storm before I could cut it to size and get it under cover. Some pieces are fine and some not so much so I am trying to mix them up when I load, but I plan on trying to boil with just dry & split small hardwood this coming weekend. I knew my wood situation was going to be the weak link this season as I didn't put the time in last summer and fall when I should have! On the plus side my 3/16" tubing is working great and I was finally able to get back to maple sugaring after a 5 year break.

I have attached a screen shot of steam exiting my stack - seems like a pretty good plume to me but I don't have much to compare it to.

[Pdiamond]

You might be better off installing the blower on the back side of the arch firebox blowing towards the front. this would improve the boil on your syrup pan and fire. Then it would follow the ramp thru the flues and out the stack. That is how my SL 2 x 4 raised flue evaporator is set up, and I boiled off 325 gallons last Sunday in 6.5 hrs, straight sap no RO. Made 6 gallons of syrup. Used wrist size hardwood, beech, ash, and maple. We fired every 6 to 8 minutes.

[Old County Road]

Thanks for the suggestion PDiamond - I will have to explore that option. It would be nice to not have the blower in the front as it is kind of in the way.

I imagine you shut your blower down when you fire so as to avoid a face full of flame?

I boiled for 23 hours on unsweetened pans to make 6 gallons. I would much rather do that in 6.5 hours like you did.

My woods have a nice mix of maple, ash, birch, and beech which is what I burn at home - I will have to put in the extra time this spring to prep the sugar house for next winter.

[Pdiamond]

I do have it switched and marked AUF. Along with it is a string of LED lights that go all around the inside of my 12 x 16 Sugar House. This lets me know when the blower is on and when its off. This was also my first boil of the year, late start. Hoping to squeeze at least another week or two in, praying for the weather to hold for a longer season. Trees are still looking good.

[Super Sapper]

It sounds like you may be adding too much wood at a time. Is there a layer of coals? If so you need to add less wood more often as the coals will slow down your boil.

[pete3046]

I have a 2x4 SL drop flue on an old Leader arch. I was getting around 12gph for the first few boils. I added board insulation and fire brick under the flues, decreasing the air space from around 5” to 1.5” along with adding a few feet of stack, from 8’ to 10’ and increased my boil by about 5gph. I should be able to get 20+gpm.

[sap seeker]

That is how my SL 2 x 4 raised flue evaporator is set up, and I boiled off 325 gallons last Sunday in 6.5 hrs, straight sap no RO. Made 6 gallons of syrup. Used wrist size hardwood, beech, ash, and maple. We fired every 6 to 8 minutes.

That is an insane rate for a 2x4, dropped, raised, or turbocharged!:D

[red/one]

I have a homemade arch with flat pans and AUF. 2'x3' and 2'x33". This year I started out with about 13gph. The wood was hickory and had been slightly wet. I changed to dry fist/wrist sized cherry on the last boil and pulled just over 20gph. The fire box is insulated and bricked, no ramp to the back pan. Its a wall till about 2.5" under the pan, then flat to the stack. The back pan was boiling pretty good. I was firing every 7 minutes and like gbeneke stated my pants got real hot when the door was open. The bricks were glowing.

[Old County Road]

Thanks Super Sapper - I will definitely try adding less wood more frequently - that should help to keep the boil from slowing down in the syrup pan. How many sticks of wood per firing would you recommend? In terms of coals I didn't really have much when I fired and what I did have I was pushing to the back of the arch under the flues.

[Super Sapper]

I try to keep the firebox approx. 1/3 full and do not add based on time. I use stack temp to let me know when I need to add more and if coals start to build up I add a few pieces of soft wood to get the coals down. The fire is hot enough that I can instantly start a piece of hardwood on fire when touching the plate protecting the door insulation when the door is open.

[Old County Road]

I will tinker this weekend based on everyone's suggestions and report back. Unfortunately my sugar house is about 200 miles away so I only get up there on weekends mostly. I am splitting my wood I am bringing from home much smaller, and I should be able to focus more on boiling as I will have help this weekend.

I should have between 400 & 500 gallons to boil by Saturday - so hopefully I can do this in 12 - 16 hours at maybe 30 gph instead of 30 to 40 hours at 13 gph!

[woodguyrob]

We finished up our season here in CT. on my SL Dauntless. Our last two boils using a 20" x 4' flat pan avg.d 11.5 GPH . It took a few boils to dial it in but wood size, timed firing and type of wood made a huge difference. Hoping to get up a little higher next year. I would think you'll be able to jack up your GPH with a little fine tuning. Especially with a drop flue are your flues sooted up?

[Old County Road]

Sorry to hear your season is over in CT. Were you able to make much while you had sap flows? 11.5 gph seems pretty darn good for your pan so you must have gotten your system down pretty nicely.

In terms of my drop flues being sooty - they were/are blackish when I started the season but it wasn't caked on. If cleaning flues is beneficial I will definitely do that for next year.

[Pdiamond]

Sap Seeker
You should see this thing eat wood. I fire every 6 to 8 minutes with wrist size wood. If I happen to get a piece that is a little larger I can extend that to 10 minutes. Even with the high sides on the raised flues you really have to watch when you are checking for foaming so you don't get splashed with the sap as it jumps. It really is quite awesome to watch.

[woodguyrob]

Old County Road; We made about 5.25 gallons so not too bad hoping for more next year. Pretty happy with the Dauntless.

Interesting post here, others have mentioned fire more often w/less wood and that's exactly what I did the last two boils. Set timer on phone for 4 minutes then upped it to 4.5 minutes and each time about 7-10 sticks criss crossed... Literally sticks & branches maybe 1' to 1 3/4 inches and up to 18 inches long. Mostly pine and dry.

I've read soot will inhibit heat transfer, not sure how much, someone with a drop flue can probably chime. I know I'll be cleaning the bottom bottom (fireside) of my pan regularly next season. I had a thick layer on the bottom on the last boil.

[Old County Road]

Update on my boiling rate - on Saturday with smaller split and drier but not super dry wood I was averaging 25 gph. I had a good pile of very dry hardwood that I started using Sunday morning - but disaster struck in the form of a massive burn up in the flue pan.

I ended up with a blob of burnt syrup about the size of football above the flues and burnt syrup almost from end to end in the flues. I was doing my first draw off of the day - much later than I should have as the thermometer was reading 3 above boiling and then quickly climbed from there to 10 above boiling and the flow pretty much stopped. Mad dash to pour sap and hold down the float ensued. End result was a burnt and warped syrup pan and burnt flue pan with some warped flues. Lost probably 3 gallons of syrup and I am estimating 30 hours of time between lost boiling, disassembly, cleaning, and reassembly.

My main mistake was being distracted and not drawing off sooner. My new rule is going to be that if a visitor stops by I am throttleing way back. Having a hood on the flue pan was also a factor as I couldn't see what was going on in there - which was one of my fears of using a hood.

I am also going to use info I have read on this site post disaster and start my first draw off at 2 below boiling in order to try to get the gradient set up. I was clearly making syrup in the middle of the pan so I will have to avoid that again.

[pete3046]

I have one thought that might help. Do you a float box setup for your flue pan? If you are boiling at 25gph you really should consider a float to get your pan at 2" plus. A separate float from the flue to the syrup pan would also be helpful so that you could then maintain the depth in both pans separately.

Pete



Update on my boiling rate - on Saturday with smaller split and drier but not super dry wood I was averaging 25 gph. I had a good pile of very dry hardwood that I started using Sunday morning - but disaster struck in the form of a massive burn up in the flue pan.

I ended up with a blob of burnt syrup about the size of football above the flues and burnt syrup almost from end to end in the flues. I was doing my first draw off of the day - much later than I should have as the thermometer was reading 3 above boiling and then quickly climbed from there to 10 above boiling and the flow pretty much stopped. Mad dash to pour sap and hold down the float ensued. End result was a burnt and warped syrup pan and burnt flue pan with some warped flues. Lost probably 3 gallons of syrup and I am estimating 30 hours of time between lost boiling, disassembly, cleaning, and reassembly.

My main mistake was being distracted and not drawing off sooner. My new rule is going to be that if a visitor stops by I am throttleing way back. Having a hood on the flue pan was also a factor as I couldn't see what was going on in there - which was one of my fears of using a hood.

I am also going to use info I have read on this site post disaster and start my first draw off at 2 below boiling in order to try to get the gradient set up. I was clearly making syrup in the middle of the pan so I will have to avoid that again.

[fisheatingbagel]

Update on my boiling rate - on Saturday with smaller split and drier but not super dry wood I was averaging 25 gph. I had a good pile of very dry hardwood that I started using Sunday morning - but disaster struck in the form of a massive burn up in the flue pan.

I ended up with a blob of burnt syrup about the size of football above the flues and burnt syrup almost from end to end in the flues. I was doing my first draw off of the day - much later than I should have as the thermometer was reading 3 above boiling and then quickly climbed from there to 10 above boiling and the flow pretty much stopped. Mad dash to pour sap and hold down the float ensued. End result was a burnt and warped syrup pan and burnt flue pan with some warped flues. Lost probably 3 gallons of syrup and I am estimating 30 hours of time between lost boiling, disassembly, cleaning, and reassembly.

My main mistake was being distracted and not drawing off sooner. My new rule is going to be that if a visitor stops by I am throttleing way back. Having a hood on the flue pan was also a factor as I couldn't see what was going on in there - which was one of my fears of using a hood.

I am also going to use info I have read on this site post disaster and start my first draw off at 2 below boiling in order to try to get the gradient set up. I was clearly making syrup in the middle of the pan so I will have to avoid that again.

Sorry to hear about that. It's hard to keep focused when people stop by asking questions when you're trying to boil. I think it's a good idea to slow things down when you have visitors; less wood, more sap in the pan.

I'm not sure how your pan setup is, but with my Smoky Lake hybrid it's not possible to maintain separate levels in the sap and syrup pan - a big drawback. That's the compromise with a hybrid pan. If I was starting over I would go with separate syrup and sap pans.

[Old County Road]

Thanks gents - nothing I can do now but learn from it. It bums me out out that the previous owner probably boiled on this rig for 10 years with out burning the pans and I managed to do it after about 40 hours of boiling.

My flue pan does have a float box and the flue pan and syrup pan are separate. I possibly could set up a float box between the two pans and if I did I would but a sight level and possibly a thermometer in that box. I am not sure if a float box between the two pans would have helped in this situation though as I think it was more operator error than evaporator error.

I had the float set to keep 2" or so of depth but will most likely raise it to 2.5" for more of a safety margin. I also plan on doing a depth test with cold sap before I put the hood back on where I will open the drawoff into a 5 gallon bucket and then measure through out the flue and syrup pan to see if the float box supply is keeping up. I didn't have any issues (that I knew of) on Saturday when I boiled for 12 hours at roughly 25 gph and I looked in both sides of the flue box every 20 minutes or so to see if I had foaming (which I occasionally did and knocked back with defoamer). I think the main issue was that I boiled hard for about 3 hours Sunday morning before drawing off anything, that I waited to long after I saw the temp was coming up, and that I did not react quickly enough when the s#t hit the fan.

[mainebackswoodssyrup]

Just my $0.02 but I think another float box on a small pan setup is just another thing to monitor that really won't do much for you other than adding one more thing to keep an eye on. Defeating the purpose in my opinion. We run 1.5"-2" deep on our 2x6 and never had an issue. I'll even run it tighter when a long boil is in progress. I know they are a lot of money but one item that takes the operator error out and provides a safety net is an auto drawoff. It would have saved you in this case. We filter, bottle, drink beers and have a good time while boiling. Sure we keep an eye on it but once you know your evaporator and have the setup dialed in for the day they do the work for you. Sorry to hear about your pans, sounds like it was a bad one.

[Old County Road]

I tend to agree on the limited benefit and potential downside of adding a float in between the two pans - it would be one more thing to monitor and something that could also go wrong. An auto draw would be nice gizmo to have. If I had an oil fired rig I would definitely have it - but with the ritual of firing the evaporator I was in the habit of checking the temp routinely to see how much it dropped after firing. I really should have been more focused on the task at hand and not allowed myself to get distracted.

[motowbrowne]

I don't see how adding a float to the syrup pan is optional. If you have a drop flue setup, I don't think you can use a float between the pans. If you have a raised flue setup I don't think you'd want to operate without one.

[MapleMike]

I'm with Mainebackswoods, auto draw off is the single best investment I’ve made in this process. I have a wood fired 2x6 drop flue and the auto draw off takes all the stress away. Wish I bought it years sooner. I think the cold sap test your going to do is smart. Hopefully the pans clean up for you.

[Sugarmaker]

Update on my boiling rate - on Saturday with smaller split and drier but not super dry wood I was averaging 25 gph. I had a good pile of very dry hardwood that I started using Sunday morning - but disaster struck in the form of a massive burn up in the flue pan.

I ended up with a blob of burnt syrup about the size of football above the flues and burnt syrup almost from end to end in the flues. I was doing my first draw off of the day - much later than I should have as the thermometer was reading 3 above boiling and then quickly climbed from there to 10 above boiling and the flow pretty much stopped. Mad dash to pour sap and hold down the float ensued. End result was a burnt and warped syrup pan and burnt flue pan with some warped flues. Lost probably 3 gallons of syrup and I am estimating 30 hours of time between lost boiling, disassembly, cleaning, and reassembly.

My main mistake was being distracted and not drawing off sooner. My new rule is going to be that if a visitor stops by I am throttleing way back. Having a hood on the flue pan was also a factor as I couldn't see what was going on in there - which was one of my fears of using a hood.

I am also going to use info I have read on this site post disaster and start my first draw off at 2 below boiling in order to try to get the gradient set up. I was clearly making syrup in the middle of the pan so I will have to avoid that again.

OCR,
Well I hope you were able to save the pan! And get back in production too. When friends arrive I try to watch things even more as I am easily distracted. A new evaporator may boil much faster than you expect. I check the float box on the rear pan every time I fire. if it has sap flowing in its a good sign. You must have had a lot of syrup in the entire rig. I have never come close to burning the flue pan. as it is usually much lower sugar content.
Good luck in the future and Keep boiling!
Regards,
Chris