2x6 Maple Pro raised flue "test boil", couple of questions

[Mudcat_21]

Hello Everyone,

We did a "test boil" yesterday and noticed a couple things with our cooker. The syrup pan is 2x2 with 2 dividers so there is 3 channels. We noticed that there was a more rapid boil in the center channel (tried to keep the fire as far to the front as we could). This concerns me that the center channel may "make" syrup before the last channel where the draw off is. Is this why a fair amount of people pull off just before you get to syrup and cook it down on another pan? We are not completely new to maple syruping but this is a "new" cooker to us.

Another question I had was in regards to reversing the flow from time to time. With this style pan we will need to disconnect the fittings and physically turn the pan by hand. How is everyone doing this without completely having the pan drain out? Maybe we didn't get all the plugs we should have when we bought it?????

Thanks for the help....

[Mark]

Yes the center will make syrup first, you have to just be aware of that and draw off early. Drain the syrup pan and turn it around before the start each day if building niter.

[Mudcat_21]

Thanks Mark for answering my questions. We have a temp probe at the draw off, So it would make some good sense to figure out how to get another temp probe in that center channel to keep track of whats going on in that channel?

[Lazarus]

We have the same issue on our GBM 2x6. It is frustrating. I have found that closing the draft door to its absolute smallest notch (the least amount open) really helps keep the heat up front and makes it a lot more even. Also making sure your wood comes all the way up front right to the door can help.

Lazarus

300 Taps and growing
GBM 2x6 drop flue with preheater

[killingworthmaple]

To keep the fire and heat foward I have put a couple of fire brick on the ash grate by the door so the air comes in a little farther back and it keeps the front of my pan warmer. I have found that with out the extra bricks the cold air rushes in by the firing door and cools the front pan down to much. This may work for you if after trying it if it doesn't work it's easy to just remove the brick.

Nathan

[Mudcat_21]

All good ideas guys that I will put to work once our sap starts running here in MN! Thanks

[nymapleguy607]

The uneven boil in the syrup pan is most likely caused by the fire not being hot enough. I fought for 2 years to get mine figured out, what worked for me was to close the amount of gap between the stack collar and the filled in area under the flue pan. This cuts down on the amount of draft the stack pulls and keeps more heat under the syrup pan. The amount of gap depnds on a lot of things like stack length, and if you use a blower. Good luck

[Flatlander]

I too have this problem. I put a damper on my flue to help regulate the outflow of gases. I have built up the insulation below the back pan to force a ll flue gasses up into the raised pan and I placed a steel shield in the back of the fire box which forces all the heat and gases up to the bottom of the front. This has helped the most for me. i also keep the wood stacked tightly to the doors. I have a 1/4" gap between the doors so I can see what the flames are doing. As long as I have flames licking up right in front of the doors, I get a good boil on the front pans.

Another idea is to alternate the wood as you stack it in the fire box. This allows the heat/flames to rise straight up instead of being forces to the back of the fire box.

Good luck.

[Yankeeman]

Hello all,
This is my first time with a 2x6 raised flue. I have such a good draft that it pulls all the fire past the syrup pan and it takes forever to get syrup started in the front pan. I believe this is also why I keep making dark syrup. I have tried reducing the draft by closing stack lid just until smoke starts seeping out the bottom, then open it just a bit. This helps the front pan, but kills my overall evaporation rate. The CDL is rated for 40 gal/hr. I get around 38 if I run everything wide open. If it is throttled back, I drop to around 18 gal/hr. After watching it burn will full draft, I had the same thoughts of placing a diverter in the firebox to redirect the gases to the front of the syrup pan before going on to the flue pan. What I don't understand is why it isn't made like that from the factory? Any ideas would be a great help. Thanks.

[chevypower]

Our middle pan always comes to a boil much sooner than the one we draw off from (5x14 oil fired). We have a temperature probe in that pan to keep track of it but as others have said I just draw off some while it is light to get the gradient flowing and once the pan we draw off from is caught up I just slowly add back in the light stuff to finish it off. If I don't do that we end up with a huge first draw that gets real heavy towards the end.

[Big_Eddy]

To the OP - I'm not sure if you have an issue. I like to have my front syrup section a touch cooler than the other sections. (I have 3 syrup sections in my homebuilt) It reduces the risk of disasters. Once the gradient is established and I'm drawing regularly, it doesn't pose a problem. It just means that I am evaporating more in the back syrup section, but that's where the less concentrated sap is coming in from the flue pan anyway.

Similar to what chevypower said - as I get close to the first draw of the day, I will pull a gallon or so out of the last syrup section and pour it back into the first to push the thicker syrup from the middle through. After that initial push everything works well and my front section is less touchy than it might be otherwise.

[mellondome]

I had similar issues when I first started on my 2X6. The 3 biggest helps...

restrict the area directly under your base stack. This doesnt get mentioned enough.. it is the #1 biggest help. I have mine restricted to 1/2 inch using firebrick.

Small diameter wood.. wrist size..no bigger!

Block off the front 6-8" of your grate . This will make the flame come forward and hit the front of your pans. Only open the doors to add wood.

Also, frequent constant fireing. You wsnt to add every 7-10 min on natural draft... 2-4 pieces at a time. Dont let it burn down to where you need to add an entire layer of wood.. this will kill your boil.

[Mike's Sugar Shack]

When i shut down my evaporator i make sure i draw off some sweet .This helps me when i start back up next time to get the flow going agin.

[Paul VT]

I had similar issues when I first started on my 2X6. The 3 biggest helps...

restrict the area directly under your base stack. This doesnt get mentioned enough.. it is the #1 biggest help. I have mine restricted to 1/2 inch using firebrick.

Small diameter wood.. wrist size..no bigger!


Block off the front 6-8" of your grate . This will make the flame come forward and hit the front of your pans. Only open the doors to add wood.

Also, frequent constant fireing. You wsnt to add every 7-10 min on natural draft... 2-4 pieces at a time. Dont let it burn down to where you need to add an entire layer of wood.. this will kill your boil.
What is your evaporation rate? I have a lightning 2x6 with a preheater and was getting about 30-35 per hour last year.

[maple marc]

Thanks to all posters on this thread for sharing ideas. I have same issues. I have been advised to build up the wood more on the draw side than in the middle. This is easier said than done. I have learned to start drawing early--first hydro cups measure light, then get heavier. All averages out, but I want the day's production to be slightly heavy, so I can adjust density downward before canning.

I have added fire bricks to the sides of my arch along the flue pan, so there is a 1" gap between pan and arch brick. I had not thought to add bricks behind the pan under the stack. Sounds interesting. Mellondome and others....can you provide more detail.....when you say 1/2"....not sure what you mean. Idea of bricks to front of grate also sounds good. So you are adding brick directly on top of the grates?

I get 30 gph, no air, with draft door completely closed. If door is open, rig gets way too hot. 10" stack.

To make life easier when you drain and turn front pan, get a couple of rubber plugs at the hardware store to plug tunnels. Also might as well clean the pan while it is drained. If your rig is like mine, with pan gasket between pans: run a stiff wire (coat hanger) through the gasket like a shishkabob skewer to keep it in good form. Also cover it with aluminum foil to prevent splatter from destroying it.

Thanks,
Marc

[mellondome]

Marc,
My 2x6 only has 8" stack.. and is raised flue.

I built up a flat area under the stack base with brick. Made it a little larger than the stack base and left about 1/2" "head" space for exhaust.

For the space by the door, I just used 2 half bricks and layed them on the grate. Not sure hiw all these work with natural draft, but helped tons with forced draft. I will add some pics later today.

[maple marc]

Mellondome, I keep thinking about the bricks you have added. Up front in your evaporator, do your syrup pan sections run across or fore and back? My 3 sections run fore and back. I'm wondering if adding the bricks up front on the grate would help me. Or....I wonder if adding bricks to the draw off side would make a difference? And thanks for photos or more descriptions of your bricks under your stack. I guess I might have 4" between the back of my rear pan the the stack. And there is maybe 8 or 9" from the floor of the arch there to the bottom of the stack. You say you fill all this in to leave on 1/2" of clearance on top?

Thanks,
Marc

[mellondome]

My dividers run length ways with the arch. I have a drawoff/float box on each side. If you fire consistently, you will have an even boil in all channels. Adding wood only to your drawoff side will actually cause more problems. It will add a cooling effect to that side as you are layering in top of the hot fire with cold wood. Then it will get roaring hot about the time you should fire again. Instead of being nice and even, you get an ip and down boil.

[Clamer33]

Mellondome, I also have a new 2x8 wood fire evap. And when doing the test boil today I had noticed that the sap pan was boiling like crazy in the front 1/3 of the pan and just barely bubbling in the back 2/3. My question is you noted that you have buildup (reduced) the height the space under the stack. Would this also help in retaining more of the heat in the area of the sap pan. I'm assuming i'm losing the boil because a lot of heat is escalating easy into the area under the stack and up the pipe?

[mellondome]

Yes. This controls how fast the heat travels through the arch, keeping the heat in the arch longer. What you currently have happening is flames hitting the flues inthe front of the pan. The residual heat is being drawn up the stack so fast that it is not transfering very much to your pan.

Think of flicking your finger through a candle flame vs holding your finger in the flame.

[Clamer33]

just another question as I talked to a more experienced veteran then me today. Would building the back up and or using my close-able cap on the top of the stack achieve the same results. Or should I try them both.

[mellondome]

Closing the stack will hold the heat inthe stack.. not the evaporator. Before building up under my stack, I tried an in pipe damper.. but it didnt work well.