a flue question

[cheesegenie]

I don't seem to understand the difference between a drop flue and a raised flue pan? Can anyone explain this please? Thank you.

[WESTVIRGINIAMAPLER]

Drop flue pan, the flues go down out of the bottom of the pan 5 to 7.5 inches into the arch where on a raised flue, the flues go up inside the flue pan. I have pics on my weblink of my drop flue and someone else could help you with pics of a raised flue pan. Here's a pic:

http://s203.photobucket.com/albums/aa160/wvmapler/Maple%20Syrup/?action=view&current=9a9f.jpg

[cheesegenie]

OK, thanks, so if I buy new pans for my homemade rig, will need to make sure there is enough clearance between rails and bottom of fire brick. Or to be safe , get a raised flue, i guess?

[RileySugarbush]

I bought the pans then made the arch.

[PerryW]

A raised flue Evaporator has a separate float for each pan; i.e., the liquid level in the back (flue) pan is higher than the liquid level in the front pan.

Also, on a drop flue, the flues hang down into the fire, so you must be careful not to hit them by throwing the wood in too far.

[Grade "A"]

I have read many post on raised vs. drop flue before I bought my pans, there are good reasons for both styles. I don't think you can go wrong with ether one. If you have a drop flue pan now and you want to put a raised flue on the same arch you will have to fill in some of your arch to drive the heat into the raised flue, but this is very easy to do.

[moeh1]

Forgive my ignorance, how do you eventually get all the syrup out of the drop flues?

[michiganfarmer]

there is no syrup in the flues. just raw sap. there is a drain in the bottom of one end of the flue pan, and at that drain all the flues are piped together

[moeh1]

I am looking around here before I plunge into this, appreciate the wisdom!:D

[OGDENS SUGAR BUSH]

not all drop flues have a drain, those that dont have to be pumped out with a siphon device

RICH

[SeanD]

there is no syrup in the flues. just raw sap. there is a drain in the bottom of one end of the flue pan, and at that drain all the flues are piped together

I've really misunderstood the location of drain in a flue pan. Thanks for the clarification. Is it usually placed at the stack end? I didn't realize a plug and joint could withstand the heat of the arch.

Is it mostly used at the end of the season when you move the last of the sap to the front pan for the final boil?

[brookledge]

With either a raised or drop flue the drain is typically located at the stack on one side. The main reason for it is just as it is called to drain the pan so it can be lifted off the arch or as you said to drain out the sap at the end of the season.
I have a raised flue and at the end of the season or during if I decided to clean, I will drain it into a large barrel and then fill the flue pan with water and will boil water in the flue pan while adding the sap to the syrup pan. At the same time it gives me an opportunity to clean the flue pan alittle while the water is heating.
Keith

[Brent]

Eugene

If you get a raised flue you can always add fire bricks, mica, insulation board or whatever under the pan to give you the clearance you want. Pretty easy.

If you get a drop flue, you could be fighting a more difficult problem to get it into the arch, raise the rails etc.

Also the deeper the flues the better. More surface area = more heat transfer to the sap. So number of flues and depth is important. The Pfaneuf rig I got last year has something like 8 or 9 flues that are 8 1/2" deep. The fire box is the same size as the Leader Half-Pint and it burns about the same amount of wood .... but it boils 5 to 6 times as many GPH. Get the most surface area you can.