Preheater plumbing question

[pobryan]

Hi,
This is my first post and my second year making syrup. I purchased a used Grimm 2x6 with a Small Brothers Lightning Preheater. I plumbed the Preheater up the same way as the previous owner which was with the cold sap flowing into the top pipe of the preheater and out the lower pipe. I have seen other posts that suggest it should be plumbed the other way around (cold sap in lower pipe, hot sap out the top. This seems to make sense except there is the requirement to have a vent to bleed off trapped air. My rig doesn't have and it doesn't appear it ever did. So my question is; should I reverse the flow and add a vent or is the Lightning designed to receive the cold sap in the top pipe?
Also can anyone tell me how to reverse the way the threads read in this forum. It shows up earliest post last for me.
Thanks for any help
Pat

[Paul VT]

Many do plumb cold in the bottom and hot out the top. I built a Preheater for my lightning and the cold goes in the top. Hot out the bottom. It has no vent and the sap is 190 degrees plus going into the float box. Some say it won't work but has worked great for me for the last 3 seasons. If small bros built it that way I'm sure it will be fine.

[WESTMAPLES]

hey pobryan or paul vt could you post some pics of those pre heaters and the size of the tubing i want to biuld one but have seen many in person to get the general idea of things like pipe size and plumbing directions i can build anything i just held back alittle when i see talk about vapor lock, and knowing not much good and lots of headaches come from vapor locking in any situation. ive got a nice steam hood over my 2x4 flue pan now just want to up the evap rate alittle

[Sugar Devil]

Hi Pat


Also can anyone tell me how to reverse the way the threads read in this forum. It shows up earliest post last for me.
Thanks for any help
Pat

You can change the way the posts appear by doing these actions. Choose the link "Forum Actions" which is located right under The "What's New" and The "Calendar" buttons above. Then once you have chosen "Forum Actions", choose "General Settings". Once inside General Settings, scroll down to "Thread Display Mode". That is where you can change the way that the threads appear chronologically for your preference.

[Paul VT]

1127111272
The ends are made from 3/4. The long runs are 1/2. The drip trays were my design but had a fabrication do them from some stainless I had. I don't weld stainless. I get a 5 gallon bucket of water so hot you can't put your hand in it every hour. 11273
I bought the hood used and made it fit the flue pan.
Sorry about the sideways pics

[Russell Lampron]

pobryan if you click on the little blue dot with the arrows in it at the left of the thread title it brings you to the first new post since you last visited. They go down in order from oldest to newest from there.

[pobryan]

Thanks for helping me figure out how to manage how I read these threads.
Univ. of VT has a paper on building and using Preheaters. Lot of good info. My evaporator is a 2x6 with a 2x4 sap pan. The preheater uses about 24' of 3/4" tubing that has 2 loop bundles. I think the easy part of building a preheater would be the tubing. The hard part would be the hood. Mine has a tray to catch condensate off the tubing bundle and a gutter around the inside perimeter to catch condensate that runs down the inside of the hood. All the condensate is then drained off. Hope my photos help. I am going to swap the inlet from the top to bottom to see if it makes a difference11316113171131811319

Pat

[Russell Lampron]

Thanks for helping me figure out how to manage how I read these threads.
Univ. of VT has a paper on building and using Preheaters. Lot of good info. My evaporator is a 2x6 with a 2x4 sap pan. The preheater uses about 24' of 3/4" tubing that has 2 loop bundles. I think the easy part of building a preheater would be the tubing. The hard part would be the hood. Mine has a tray to catch condensate off the tubing bundle and a gutter around the inside perimeter to catch condensate that runs down the inside of the hood. All the condensate is then drained off. Hope my photos help. I am going to swap the inlet from the top to bottom to see if it makes a difference11316113171131811319

Pat

My Algier hood and preheater is basically the same as yours. I have the cold sap go into the bottom and come out of the top. What I did is install a needle valve from a refrigerator ice maker kit to the upper pipe just as it exits the hood for a vent. I attached a piece of 1/4" copper tubing to that and ran it out to my feed tank so that any sap that escapes through the vent goes back into the tank. The only time that I have vapor lock issues is when the feed tank is almost empty.

[pobryan]

I completed my conversion yesterday and today we will see how it works. For a vent I used a 3/4x1/4 T. 1/4" line comes out the top and elbows to horizontal. Then I attached another 1/4x1/4 T. One leg facing up and the other down. The down leg empties into the float box. My hope is that air will vent out the up facing leg while sap will run down into the float box. if it works I'll take a photo, if not it's back to the drawing board. I considered using an air purge for a boiler but I thought it might fail from sugar build up as it has moving parts.
Pat

[pobryan]

11393
Here is a photo of the vent I rigged up for my preheater. The vent is all 1/4 copper with a piece of sap line running down to the float box and another short piece pointed up in the air. The upper piece is to contain any hot sap that venting gas shoots upward. It kind of percolates once in a while but the plastic 5/16 line is enough bigger than the 1/4 to let the water column to break and run back into the float box instead of shooting up in the air.
Now I think I need a secondary float box between the tank and the evaporator to ease the pressure of the flow as my supply tank is about 6' above the evaporator.
Pat

[pobryan]

After running my rig a bit with the preheater vent set up so it dumps into the float box it seemed to add enough sap so the float was trying to shut off the supply line to maintain a proper level in the sap pan. So with the secondary float box in place I simplified the vent to vent into the float box.11550 Now with the head pressure reduced and regulated by the secondary float box (tractor supply pail) and the modified vent the rig just purrs along. No fiddling with the float to maintain a proper level which was a constant concern before and the sap coming out of the preheater is wicked hot. Also making lots and lots of hot water for clean up.
Pat

[rayi]

I have a preheater by Patrick Phanuf. The cold goes in the bottom and the hot (180-200 degrees) comes out the bottom. The large tube has a 1/2 inch fitting that goes straight up. I attached dairy hose to it to above the feed tank. It vents and I also know how nuch is in the tank