Preheater and hood

[Outdoorsman0490]

I have been looking at past threads for a while and have not found exactly what I was looking for.
I got my 2'/5' smokey lake hybrid pan recently. I want a preheater and hood, but buying one is not in the cards, I am going to make them. I plan on making the preheater to sit over the flue pan, with the hood and keep the syrup pan open. I have found that 3/4" copper is fine for the preheater, but how many feet of it should be used? Is having 6 3' pipes with manifolds on either side enough, or should I use more?
Any other input or pics would be great. And planning on a simple home made plastic/wood hood.

[nymapleguy607]

On my 2x6 I run 8 pipes, 4 wide and stacked together, tied in at the manifolds. The bigger the preheater is the more surface area it will have to catch heat and heat the sap.

[Outdoorsman0490]

And you want to have the inlet be lower than the outlet to the float box, with the vent on the high side right?

[BreezyHill]

My system was a 1.5" double copper that was in a wooden box. The steam from the hood(home made), ducted the stem to the box that was on the sugar house wall about 3' from the evap. The heat exchanger lay raised in the bottom half of the trough and the steam would be drawn up the slight incline to the top return trough that was connect to a 6" stack. 6' of 6" straight up into a 8" that went outside. This transition made a venture that helped pull the steam thru the trough from the hood. Worked great for the last 30 years but two nights ago I found a end plug is corroded and will likely leak. So I am changing the cooper to stainless 1.5" and hoping that the reduced heat transfer will not adversely affect my end temps. The previous unit would dump out 190 degrees to the float box.
Realizing it likely will I am going to insulate the float box and make a cover for it so that I can retain the heat while still allowing steam to escape.
Out of my system I get about 5 gallons an hour of condensate. This is my hesitation to put the preheater over the flue...don't want to have condensate drip in the flue pan.

Good Luck!

[nymapleguy607]

Yes vent the top of the preheater, if not they can vapor lock and cause big problems. My sap comes in in the low end of the preheater but then it returns that way to. It was easier to tie into the float box this way.

[Outdoorsman0490]

If I were to have the low/infeed of the preheater towards the front of the pan and 6" above pan; and had the outlet/high end in the back of the flue pan terminating in the float box, about 9 or 10" above the pan; is there enough angle on the preheater to make the condensation flow down hill towards the front, where I can set up a diverter to a collection location? Or, will the condensation still just drip back into the file pan.

Right now I am thinking 9 3' sectionsof 3/4" copper for the preheater over the flue pan. The evaporator is supposed to do 25-30gph. Do others have the preheater/hood just over the flue pan, or over the syrup pan as well. My evaporator is 39" of flue pan and 21" do syrup pan.

[BreezyHill]

In my flue with the hood closed the bubbles will jump past the top of the pan. So a preheater would need to be above this point...unless the bathing of the heater would heat it to a point that condensation would not occur. I am totally not sure at what angle it would need to be at to keep the condensation from dropping off, but run down the tubing. I would think you could run a trial in the kitchen and find the answer with a section of the tubing filled with cold water over a pot of boiling water. This may help with the designs.

Ben