Why is my 2x6 going slow

[MKR VT]

I have a leader 2x6 pleasure model from around 1990. I have a preheater running sap in around 185 degrees, and I also have a blower underneath. The doors glow red throughout most of the boil. I run my pans between 3/4 and 1 inch deep. My best boil rate this season was around 28 gph. but for the season I averaged just below 25gph, with a lot of hours spent boiling around 21 gph. This just doesn't make sense. I know two other guys in the area with 2x6's who are running well over 40 gallons per hour. I burn mostly hemlock, good and dry, but tried hardwood also, with no help. What is wrong?

[HanginAround]

How far are the bottoms of your flues from the arch? Maybe you have too much room. Raised or drop flues?

[Fred Henderson]

What is the percentage of sugar in your sap. If you are below 2% it will seem like you are boiling a long time.

[softmaple]

do you clean your flues between each boil?

[John Burton]

how fine do you split your wood? i shoot for nothing larger than 1x2 keep the firebox no more than 1/2 full with plenty of air spaces and only keep the wood over the grates (not against the sides of the arch ) when you fire the wood pile should be shaky ( if it is solid you are feeding to fast collapsed and your to late) remember its a 2x 6 and only rated for 30 gal an hour and if your avg is 28 your not to far awawy from peak. I just got rid of mine after 3 years and i would avg 30 an hour on short stretches i could get 40 but trying to keep that up can be hard if you are not focused

[tapper]

I ran a 2x6 leader pleasure model for 10 years and your averages are just what I would get with mine. Yes you have to be particular how the wood is placed in the firebox and quality of wood is a large factor in its performance. But my boil rates would vary largly through out the season. the conditions of the day make a big difference also. I averaged 75 gph on my new rig for this season but I had one day recently when it hit 104 gph for the day. I am sure the weather was a great factor for the high gph that day.

[MKR VT]

My wood is definately sized small enough, and compares to what I see others firing their 2X6 with. My bricks are within 3/4 inch from the flues. I fire the box about half full, and seem to have very good air movement through the load. Sugar content has nothing to do with my calc of GPH. I went from tank measurements for GPH. I know that the 2X6 is rated at 25-30 gph, but I have the preheater, hood and blower. I would think it would make a significant difference. My average is 25 gallons at best, I have never hit 30 GPH.

Does cleaning the soot from the flues make a big difference?

[MaplePancakeMan]

i feel for you, i was getting bad GPH with my 2x6 for most of the season 23gph as i boil outside with no preheater or blower. I realized i was putting wood too far back in the box. The last two boils i concentrated on keeping it stacked 20" long 3 pieces straight back then across and then straight back leaving a square air gap in the middle and sides i filled the box 1/2 to 2/3 full and the last two boils i was getting 34gph outside. I tried firing every 7 min it also cleared up all my flue problems with sap flying out as the heat wasn't so concentrated back there but still kept a good full pan boil.
Maybe that helps, Or maybe it ends up as a rant. Either way i hope you get things worked out.

[maple flats]

Keep the firing every 7 minutes, filling only half at a time and alternate. Mixing with good dry hardwood will help. I found about 2/3 hard and 1/3 soft works good when I have soft slab to get rid of. The hemlock has fewer BTU's for the heat and I don't know what the firing rate should be if all hemlock but it would likely be less than 7 minutes. I found that firing sooner than 5 minutes was counter productive because the boil rate lost when the doors were open didn't recover soon enough to make up for what was lost during fueling. When you fuel do it as quickly as you can to reduce door open time. Make sure you are catching all condensate from preheater and running it out to a container. If you have a hood which is usually the case with a preheater, be sure you catch condensate from the hood and stack as well. I have a hood over my entire evap (3x8) with the syrup pan part about 16" above the pan and use 2 steam stacks 12" each. During cleanup when i am boiling water I remove my condensate catch for the steam stacks and my rate drops about 15-20% (I also use this when finishing my boil in the evap by draining the flues pan, filling the feed tank with water and then adding flues concentrated sap into the syrup pan, this is actually where I notice the evap rate drop, during cleanup I am not really boiling, just getting things hot and brushing them down) On another note, are you sure the preheater has not airlocked on part if it is a parallel type. You can see this because not all runs have lost of condensate drips during use. If this might be the case make sure you have the inlet lowest and outlet highest with the whole thing sloping up across the parallel runs towards the outlet. Then the outlet should drop as straight as possible to the float valve. These little things can sometimes be hard to find but examine every thing you are doing and the cause or causes will be found. Good luck.
Dave

[WESTVIRGINIAMAPLER]

I think one of the things that hurts you is that you have a 3' syrup pan and a 3' flue pan vs a 4' flue pan and a 2' syrup pan which is what most 2x6's have and would probably give you at least another 5 gph.

[RileySugarbush]

My new rig is a 2x6 arch, with a 33" long half pint syrup pan and 3' sap pan with 7" drop flues and 3' steam hood/ preheater. This year I burned all red oak, split to an average size of about 4". It boiled 30 gph without despite distractions. I do have a 190 CFM blower going full tilt, and a square firebox.

[danno]

MKR VT-

I'm convinced that just the way it is. I can only get 50 GPH out of my 30x8 when others are able to get 80-90 GPH. I've got all the go-fast tricks as well. I'm convinced my water meter is bad, but the sap to syrup ratio does seem about right.

[brookledge]

Brandon hit the nail on the head. There will be a big difference with a foot longer flue pan. Is the rating of 25-30 with 3 foot flue pan or 4 foot flue pan?
Also my experience, I have gotten higher boiling rates by keeping the soot brushed off the pans. Having soot build up is just like having thicker steel used in the pans. Manufactuers use the thinnest stainless they can while maintaining the integrity of the pans. If you made pans with 1/4" they would not boil as fast. So keep the soot down and get the best heat transfer as possible. Think of it this way that thin layer of soot is acting like insulation.
Keith

[softmaple]

i find it also boils faster with the shack door almost closed, with just enough to create a draft out the roof