Another Preheater Question

[SeanD]

I have a preheater pan that drips into the back of my evaporator. This year I kept it pretty shallow with the thought that whatever is in there will absorb heat from the bottom faster if there is less liquid to heat.

It seemed to work out well for the most part, but whenever the boil got away from me and I had to really flood some sap in, the 1-2 inches of the sap that was in the preheater was warm, but the cold stuff was right behind it and seemed to defeat the purpose.

Do people generally keep the drip pan-type of preheater full or close to full or is shallow the way to go?

Sean

[Brent]

I assume you're using something like a Half Pint with a pre-heater sitting on top. We did that last two years and didn't like the amount of dripping. Best idea I've seen was what Uncle Tucker did. Find a post from him and hit the links to his pictures. Last time I looked he had his new evap and pix of his old Half Pint. He hung the pre-heater off the back and used stack heat. I would go a small step further and put some sheet metal of simple foil around the stack to get even more heat. This keeps the drips outside.

The other idea was a custom preheat pan that was a touch wider than the pan it sat over and had a sloping bottom so all the condensate ran off to one side. Sorry, can't recall where I saw that one.

[SeanD]

That's what I ended up doing. Here are some pics of the set up. I'm reconfiguring it for next year, but the preheater will still sit over the last bit of stack heat. How deep did you run your preheater?

Sean

[barrelstove]

my warming pan/feeder pan/preheat pan/whatever you call it still sits over the back of my main pan but i plan on making somthing to hold it over the stack, and actually i want to build some sort of air box to gather the heat from the stack. mabey even extend my arch under it, im still designing that part.

as far as how deep to run it, i keep mine as full as i can. eventually it all gets warmed up. ive had mine as warm as bath water before. what i try to do is add small amounts of cold so i dont get a big temperature drop. thats my approach.

[Harken]

Sean, This was my first year using a pre-heater pan. It sat on top of my pan, right in front of the stack. Temps got as high as 120F. I would fill it to the top, then refill when half empty (a pail full). With this temp, I was able to keep the pan (2x4 - 3 channel) at full boil. There was some condensation dripping back into the pan, not sure if it was a significant amount.

Ken

[Gary R]

Barrelstove,
This is my first year and this is what my preheater looks like. It's a pan sitting on another box I made to transition the flue gasses to the pipe. It works great. A needle valve regulates flow to my pan. My only problem is that it gets in the way when I remove the pan for cleaning.

[barrelstove]

hard to tell from the pic, but does the copper tubing carry the sap down into the pan? mine just drips. i should have gotten a picture when i boiled today.

the pan is a small brothers and was all setup when the set came to me.

do the flue gasses flow through that box or is it just there to keep the hot air from getting away?

[Gary R]

click on the picture and it will be full screen. A SS nipple is welded to the bottom. A needle valve and copper tubing are connected to it and drain the preheated sap to the back corner of the pan. I have seen 180+ with a few inches in the preheat pan. When my rig is running well the valve is all the way open, flowing as much as the 1/4" tubing will handle (10gph). Flue gasses go directly into the lower pan. There is a large hole in the top of the lower pan so gasses come in direct contact with the preheat pan (thanks Jim Brown). I could have just made a longer syrup pan but, this way I can run 1" in the syrup pan and can dump 5gal. in the preheat pan (6") and walk away for 10-15 minutes.

[barrelstove]

my dad and i have tossed ideas back and forth about how to heat the preheat pan. i had though that an extention of the arch with flue gasses running under the pan would work best (like yours). dad thinks that a horizontal extension of the flue with a box around it to hold the hot air coming off the flue would work as well, plus it wont have the soot collection on the bottom of the pan.

I still havent made up my mind which way to jump, but i have all off season to worry about it.