Raised flue vs drop flue

[Brent]

Call for help from a "flat panner" who is looking to become a flue boiler.

What are the pros and cons of raised flue vs. drop flue?

Without having used either one it seems a drop would be harder to empty for cleaning but may be a bit more efficient.

Any comments would be appreciated.

[the old guy]

Brent

I Was A Flat Panner For Years And Happened On A Good Used Drop Flue 2 X 6. The Best I Could Do In A Flat Pan Was About 10-12 Gph. The Drop Flue Is Now Running Between 30 & 35 Gph. As Far As Cleaning Goes The Drop Flue Has A Flue Drain Pipe Making It Really Easy To Drain And If You Buy A Flue Brush, Cleaning Between The Flues Is Pretty Easy. Royal Maple Did A Great Job Of Explaining How To Operate And Clean This Rig For Me. I Am Pleased With It!

The Old Guy

[Dave Y]

Brent,
I have always boiled on a raised flue. I like it because I never used anything else. My biggest concern with a dropflue is whackin the flues wit the wood when you are firing. I boil a 120gph with my 3x12 and feel i could do better.

[jemsklein]

if i were to buy new that would be my biggest concern aswell but if i were to get a set cheap then i would learn to make it work but im sure they boil the same if you have them set up right

[brookledge]

I have boiled with both. I presently have a raised flue and the biggest reason for me was cost. When I bought my current evaporator in 2002 the same size drop flue was considerable more money than the raised flue. As far as boiling rates mine is 3 feet wide and both styles have the same amount of flues. I have been told that usually when you get to the wider like 5' and 6' pans the drop flue style has more flues than a raised does and there fore more boiling capacity.
I had a 2X6 and a 3X8 drop flue and never had a problem of hitting the flues with wood. The drop flue requires only one float whereas the raised needs two.
The drop flues are easier to clean (soot) in between boils with a flue brush. And are very easy to look in with a flash light to inspect for leaks.
Do a search as this topic has come up before but for alot it is just preference and what you are comfortable with.
Keith

[OGDENS SUGAR BUSH]

raised flue is easier to drain between boils during freeze up

RICH

[brookledge]

Rich
Why do you say that?
My Drop flue had drain valve just like my raised does.
I could understand if the drop flue pan didn't have a drain valve
Keith

[WESTVIRGINIAMAPLER]

I would think the drop flue would be easier to drain because it has a LOT less liquid in the flue pan vs a raise flue.

[Brent]

all the pictures I have seen of drop flue pans that were taken from the bottom view, ie through the firebox doors, did not show any interconnecting pipes or channels between the flues. So I am thinking you have to suck out the last sap or tip up the whole pan. Is this the case or do some makers interconnect them with a drain ??

[brookledge]

Brent
I can only speak for the two previous drop flue pans I had and that was that they have a manifold (not sure on the name) that connects all of the flues together near the base stack and you screw in a pipe with a valve that comes out the side of the arch. I boiled with drop flue from 1979 to 2001 and never had a problem with them
Keith

[gmcooper]

On a drop flue the stack end of the flues are all plumbed together and there is a drain connected that is piped right thru the sidewall of the arch. Very easy to clean and drain. We are on our 3rd drop flue. We got bigger each time. Never damaged a flue yet with wood. Maybe drop flues are a little tricker to run as you have only one float but then again with raised you have 2 floats to watch out for. If anything drop flue is lower to ground and easier to see in. . When we ordered our newest we talked quite a while with Leader to get what would work best for us. When they knew we had a drop flue that we liked, they didn't hesitate to recommend another one.
Personal preference i guess

[Father & Son]

I just went from a drop flue to a raised flue. The drop flue I had was old and did not have the flue drain. I had to siphon each flue with a piece of tubing to drain the pan before freezes. No specific reason for going to a raised flue other than availability. At the end of this season I will be able to compare, but at this point raised flue is brand new to me.

Jim

[OGDENS SUGAR BUSH]

BROOKLEDGE
my pan doesnt have a drain in it and the flues arent tied together to drain it so i have to use a drill with a pump or build a fire every day to warm everything up. but i do like the part of it being lower and easier to see in

RICH

[Valley View Sugarhouse]

If you can not decide what to get then get the new Leader Max this is a drop flue/ raised flew combination. 6" dropped and 5 1/2" raised they claim this will do about 240 gal an hour on a 4x12 with a 7' flue pan versus 160 gal an hour on a drop flue rig of the same size..

[Brent]

Leader Max ????? hey I only had 80 taps last year .. and I'm dreaming of maybe reaching 200 this year.

Gee with that I'll be back in the house with the wife in no time.

[jemsklein]

now that would be alot more faster to boil with its like double the surface area that would be a nice toy to have

[WESTVIRGINIAMAPLER]

I talked to a guy a couple of years ago that was field testing on of the Max pan systems before they released them to the public and he was running 300gph and sometimes more on a 3x12 with a steamaway and that is with an inferno arch.

[VA maple guy]

OK, y'all have now confused me. I recently bought Jim's (Father & Son) old leader 2x6 drop flue. I think I remember reading some post a year or two ago about most of you guys leaving your pans sweet all season. Now I'm
reading that some of you are siphoning your flue pans empty before a
freeze,what gives? Gerry

[Father & Son]

Gerry,
I tried to always be safe. I may not have needed to drain the pans but I did. You know, Murphy's Law, it's me that something would happen to.
When I drained the pans on that rig I first put both plugs in the flue pan and drained it into one bucket then drained the syrup pan into another bucket. What comes out of the syrup pan may get slushy but won't freeze hard. When you're ready to boil again just dump the contents of the buckets back into the same pan you took it out of and you're back in business.
That rear pan doesn't have a flue drain(too old) so I siphoned each flue with a piece of 5/16 tubing. Only takes maybe 5 minutes.

Jim

[markcasper]

Had to chime in on this. Back in November we had a quite a wind and it blew some of the tin off my sugar shack roof. We then got a couple inches of rain and then froze up good the first of december. Down to below zero for several nights.

I knew the tin blew off, and the pans were below. When I was scrubbing and washing the pans in October, I thought I left the flue drain open, along with the attached hose to drain the water outside. For some reason the valve was shut and the darn flue pan filled up with rain water, just about to the top of every single flue.
I discovered a frozen mass about a week after the cold spell. Boy was I worried. I put a small space heater in the arch and left it overnight. The next day it had thawed out completely and was pleasently relieved to see that nothing ruptured or leaking.
It sure shows how heavy built these pans are and especially after seeing this.

[andrew martin]

Last year was my first year with my 3x8, and after three or four boils at the beginning of the season, it turned really cold for 18 days straight. I did not have time to drain my pans and everything froze solid. When I cranked back up, I warmed it up slowly and never had any leaks. My disclaimer is that I would never do this again, and will take precautions this year to drain my pans if we have an extended cold spell.

Andrew

[Fred Henderson]

I know a guy that has a Leader 3x5 drop flue and he put a light bulb inside his arch. He didn't say if it was a heat lamp or not. But he did say that he buld keeps everything from freezing.

[mountainvan]

For 15 seasons I've had sap freeze in various evaporators, never had a leak. Sure water expands when it freezes, but it will go the way of least resistance, up to the air. Plus ice is less dense than water, and the sweet in the pan, so it floats to the top taking pressure away from the flues. If you've ever taken ice out of the pan there's a layer of sugar between the pans and the ice in the flues. Now if I had an old tin pan, I would drain it.

[ibby458]

I've boiled with both, but like my raised flue better. Two floats are twice as much bother as one, but I get better level control in the front pan and faster response to a drawoff. If you like keeping a minimum depth (like we do), it's an important point.

It is harder to clean the flues (And it sure do make a difference in the boil rate if you don't!), but they make a special offset brush just for that purpose.

[WESTVIRGINIAMAPLER]

Gerry,

Where you are at, I doubt you will have to worry too much about draining the pans. I never drain mine. If it gets extremely cold, I will burn some paper and a few pieces of bark and scrap wood every couple of days to be safe. I am in a little artic zone that is a couple of miles wide and 5 or 6 miles long. Probably not neccessary, but it don't take but a couple of minutes. A light bulb in the arch where the syrup pan ends and the flue pan begins works good too as I have tried that and been happy with the results and uses hardly any electricity.

[VA maple guy]

Thanks guys, you have put my mind back at ease. My pans are older
tin pans so i was kinda worried. I like the idea of building a small
fire or using a light bulb in the arch. Gerry