Raised Flu vs Drop Flu

[HannahL]

I have been a very small operation for several years using a small flat pan and I am looking into a 2x6 of various models and configurations. My question is what would you prefer and why? What is the difference in boiling rate?

Thanks

[MapleMark753]

First, what what I've seen, read and heard, either one of similar size would do you fine. Boiling rates can be similar. I like the raised flue, it just makes sense to me, and cleaning it out is a breeze with the drain at the corner of the flue pan. Some, but not all drop flues have a drain at the bottom of the flues. Just note that BOTH have passionate defenders and proponents, you'll probably come across this as you talk with people and research. I'd just suggest you find one you like, with the features you gotta have, with a competitive price, and get that. This is only a guess, but if you're thinking of buying new for this coming season, you MAY not find what you want now. Normal waits can be in the months long range. Good Luck!

[wiam]

I have seen smaller drop glue pans with no drain. DO NOT GET ONE OF THOSE.

[sap retreiver]

I like my raised flue. Cleaning is easy, seems that operating is easier and very hard to hit with wood. Just my opinion

[maple flats]

I started with a flat pan 2' x 3', then I got a drop flue 2' x 6' and then I got a 3' x 8' raised flue. I like the better control I get with a raised flue. I believe you will find that in any given size a raised flue gets better boiling rate than a drop flue, but the difference is slight.

[SeanD]

I have a drop flu and if I had to choose again, I'd get a raised. I'd like to have the ability to have different levels in the different pans. The other factor not mentioned yet is that raised are usually a bit more expensive.

[wnybassman]

From what I have learned here raised flues can tolerate freezing a little better between boils also. I have a small raised flue unit and don't worry too much with just a light bulb in the firebox during hard freezes.

[VT_K9]

We went from an older raised flue 2X6 to a Leader WSE 2X6 drop flue. Our tin pan was seeping and the trade to a new WSE was very enticing. I think the shiny part was the nicest part as I look back. However I see the discussion points for the drop flue and have to agree the extra surface area can be helpful. The WSE is a single float system...not as much control as two float. This is where I believe I noticed a difference. The WSE is a nice unit for smaller producers.

Our WSE does not have a drain manifold in the drop flues. You see this in the larger or higher end units more often. I am not sure if it is now available in the WSE, but I think it is. This would be a requirement in any drop flue pan for me in the future. Right now we have a 1/2" PVC pipe with the end ground to match the contour at the bottom of the flues. It works, but the manifold and drain would be much nicer and convenient as we are now draining the pans every 10-15 gallons of syrup.

Right now we have 400 taps on vacuum and a RO. The WSE is recommended for 150-200 taps by Leader. I would look at each manufacture and the ratings they show, check the manufacture/model here and on the web for customer satisfaction, and finally are the reasonable range of ratings okay for your goals. Maybe you can find a hood, preheater, blower type option to up your ratings later (GET an insulated arch door up front if you want to upgrade to a blow). Start looking at the signature lines on the site and send IMs. I have not found anybody on the site to be less than helpful.

Most importantly the MB (Maple Bug) will bite and you will probably seek more or bigger. Find something that can be expanded, sold with little loss, or big enough from the get go with expansion for the impending MB. We are expanding this year to about 800 taps with goal of 1-1200 taps later. After this year we are retiring the 2X6 and moving to a 3X10 drop flue, hood, pre heater. The advantage for us is the 2X6 is a very popular size around here and selling it should be pretty easy.

Good Luck,

Mike

[OGDENS SUGAR BUSH]

I have used both drop and raised, I prefer raised, 1 drawback on raised is its hard to brush the flues and do a decent job of it

[maple marc]

Hi Mike,

I have a Leader 2x6 WSE and always appreciate sharing ideas. I'm curious about your comment:

"Right now we have a 1/2" PVC pipe with the end ground to match the contour at the bottom of the flues. It works, but the manifold and drain would be much nicer and convenient as we are now draining the pans every 10-15 gallons of syrup."

Not sure what you mean by this. I agree, without a drain plug, draining this pan is a real pain! Are you grinding a "V" in the end of a PVC pipe, then using a pump or siphon? Details? I siphon but it's not easy.

BTW, what is your evaporation rate? When I'm really cooking I get about 30 gph. That's at a stack temp of about 900.

Thanks,
Marc

[VT_K9]

Hi Marc,

We have use about an 18" piece of 1/2" PVC to suction the sap out. The tip is ground to be similar to the shape of the bottom of the flues (mostly a "V" with the bottom slightly rounded). We run that into a PVC glue to male fitting. That runs into the hose ball valve (to control flow when moving from flue to flue and not loose the suction). We use a Wayne pump to remove the fluid. We have several of the Wayne pumps and one we use solely for this purpose. The output will go outside to drain on the ground with water and to a 5 gallon pail with sap. We fill the pump to prime it with sap or water and then keep the prime using the small hose ball valve. It works very well.

As far as evaporation goes we are probably about 25 gph. The stack temps are near 800 degrees for us. We use mostly hemlock with some pine for wood. We made a few "ripples" in the sand last year to create some turbulence under the rear pan last year. Basically keep the higher temps under the pans and not going out hte stack. Our door is likely a weak point since it does not seal very well. We do not use air since the door can already turn red hot without it. It may increase our evaporation rate, but we are not looking to warp the door that much. It would be nice to have a sealed insulated arch. But we are stepping up the game after this season and going to a 3x10 oil fired CDL Deluxe.

Season's almost here.

Mike

[maple marc]

Mike, thanks for the pumping ideas. Which Wayne do you use?

Marc

[Russell Lampron]

I went from a roasting pan on a gas grill to a 2x6 raised flue so the only real experience that I have with a drop flue is from when I ran somebody elses. It didn't take long to see the advantages of a raised flue. I don't have to worry about the sweet from the front pan flowing into the back pan and I don't have to worry about hitting the flues when firing. I just toss the wood into mine, there's nothing there to hit. My recommendation is to get a raised flue.

[WESTVIRGINIAMAPLER]

From anyone that first boiled on a drop and then went to a raised flue, I doubt anyone ever said they wish they could go back to a drop flue.

[1arch]

Hi Marc,

We have use about an 18" piece of 1/2" PVC to suction the sap out. The tip is ground to be similar to the shape of the bottom of the flues (mostly a "V" with the bottom slightly rounded). We run that into a PVC glue to male fitting. That runs into the hose ball valve (to control flow when moving from flue to flue and not loose the suction). We use a Wayne pump to remove the fluid. We have several of the Wayne pumps and one we use solely for this purpose. The output will go outside to drain on the ground with water and to a 5 gallon pail with sap. We fill the pump to prime it with sap or water and then keep the prime using the small hose ball valve.
Mike

I use the air pump on my filter press to suck sap out of the drop flues. Nice thing about the air pump is that it doesn't care about losing a prime when transitioning from flue to flue and it operates much like a vacuum when sucking the last bit of moisture from the bottom of the flues.

[VT_K9]

We use the Wayne WAYNE PC4 1/2 HP Cast Iron Multi-Purpose Pump With Suction Strainer (the title is from Amazon). They work great.

[afretired]

For cleaning my drop flue pan I run the suction line from my shop vac into one bung hole on a 55 gallon barrel and then run another vac hose with one of those small narrow cleaner ends that fits between the flues, into the other bung hole. So the shop vac sucks on the 55 gallon barrel and the other hose sucks the liquid out of the pan. The liquid then goes into the barrel. It’s easier than having to empty the shop vac every few minutes.

[SeanD]

Patrick Phaneuf designs his drop flue pans with a bottom drain. That eliminated that concern from my decision making. It's great to just open a valve to drain the back pan. If I didn't have that, I think it would have been enough to push me to get a raised flue. I highly recommend his work - although it's very likely too late to get an order in for this season.