If you have a float box, can your pre heat the sap?

[Swingpure]

Later this year, my new pan and float box will arrive. I will set something up to have my head tank, at least 2 feet above the float box.

Is there a way to preheat the sap for a float box if you do not have a raised pre heat pan that feeds it?

I debated adding two bulkheads, with fittings, to a pot, one on top side of a pot and one near the bottom side of the pot, and have the feed pipe coiled in the pot. I would boil water in the pot on an induction stove.

Thanks

[Swingpure]

Bump

I am still interested in what others do to preheat their sap prior to entering the float box, if you do not have a raised preheat pan?

[DRoseum]

Gary - many people use a coil around the stack to preheat sap going from the head tank to the float box. Words of caution...
make sure it is sized appropriately to keep up with feed flow needed and that you don't overheat it and turn it to steam and choke the flow to your evap. Also, I know many people use copper tubing, but would recommend stainless for multiple reasons (cleanliness, corrosion resistance, non leaching etc).

I used to use this approach and it worked well.

Last year I changed to a head tank that sits elevated on my arch behind my flue pan and on the way to the exhaust stack which is immediately behind this tank. I feed from my RO into that tank and it preheats there before moving to float box. I run my RO into the tank at approximately the same rate I am boiling off at and try to keep it at about 6 inches of depth for consistency to heat, but it holds 13.8 gallons so I have plenty of margin.

I am on nat gas so I can shut down quickly when that tank is nearly empty (and have a level sensor that automates this shutoff). For wood, you would need to monitor that type of setup closely and have a bucket of water handy of necessary. You can't run this setup with that tank empty....ever.

[Swingpure]

Gary - many people use a coil around the stack to preheat sap going from the head tank to the float box. Words of caution...
make sure it is sized appropriately to keep up with feed flow needed and that you don't overheat it and turn it to steam and choke the flow to your evap. Also, I know many people use copper tubing, but would recommend stainless for multiple reasons (cleanliness, corrosion resistance, non leaching etc).

I used to use this approach and it worked well.

Last year I changed to a head tank that sits elevated on my arch behind my flue pan and on the way to the exhaust stack which is immediately behind this tank. I feed from my RO into that tank and it preheats there before moving to float box. I run my RO into the tank at approximately the same rate I am boiling off at and try to keep it at about 6 inches of depth for consistency to heat, but it holds 13.8 gallons so I have plenty of margin.

I am on nat gas so I can shut down quickly when that tank is nearly empty (and have a level sensor that automates this shutoff). For wood, you would need to monitor that type of setup closely and have a bucket of water handy of necessary. You can't run this setup with that tank empty....ever.

I was originally thinking about wrapping a pipe around the stack, but was worried that the sap might stall there, if the float box did not allow it to pass, thereby scorching the sap in the tubes.

I will have to see how I could do an elevated pan behind my divided pan, on a cinder block arch.

I still think my boiling water idea has merit, as I could get the sap pretty hot without boiling it. I would have to keep adding water to the pot.

[Swingpure]

Is something like this, with the preheat pan above the divided pan and dripping into the divided pan, better than having the feed tank feeding a float box?

https://share.icloud.com/photos/048vYHghzDj_GlByXatRZLNKg
https://share.icloud.com/photos/013zk606iZnZM2vIJ7--Gm8aw

Thanks

[DRoseum]

Many people use this approach and it works pretty well.. however I'd still use a float because it actually keeps the right feed flow going for you automatically. The trickle approach is gauged by sight and that can be tough to get just right due to impaired visuals in all the steam and the limitations of matching the flow thru a valve to what your evaporation rate is (and as it fluctuates).

The pan above with trickle will preheat your sap a little and you could always feed from that into a float box. Lots of options.

[Swingpure]

Many people use this approach and it works pretty well.. however I'd still use a float because it actually keeps the right feed flow going for you automatically. The trickle approach is gauged by sight and that can be tough to get just right due to impaired visuals in all the steam and the limitations of matching the flow thru a valve to what your evaporation rate is (and as it fluctuates).

The pan above with trickle will preheat your sap a little and you could always feed from that into a float box. Lots of options.

Thanks, I am discussing some options with my pan maker.

[Kbrooks80]

Are you planning on having a steam hood? I put a 25ft copper coil in my steam hood then feed that into my float box. This has worked great for me. I did have the pipe on the stack before the hood but was always worried about the scorching. now I don't have to worry and my sap usually runs about 110 deg.

[maple flats]

With a steam hood on my back pan I made 3 different pre-heaters over the years, all before the float box. My last one had slightly over 40' of copper tubing under the hood. As it flowed into the float box I had a thermometer. This was on a 3x8 evaporator, the incoming sap ran about 170F unless my auto draw was open, drawing syrup. In that case the temperature dropped to between 110-120F because the flow thru the copper was too fast to get the full heat.
On earlier ones I had no thermometer to see how effective it was.

[BoerBoel]

...40' of copper tubing under the hood. As it flowed into the float box...
What size copper pipe did you use? What size was the inlet of your float box?
If the copper pipe was smaller than your float box inlet, was there any concern of not being able to supply sap to the float box quick enough especially when your auto draw was open?

[Swingpure]

Are you planning on having a steam hood? I put a 25ft copper coil in my steam hood then feed that into my float box. This has worked great for me. I did have the pipe on the stack before the hood but was always worried about the scorching. now I don't have to worry and my sap usually runs about 110 deg.

I don’t have a steam hood and likely will not get one for the foreseeable future. Could I suspend the pipe just above the pan and get heat from the steam coming off the pan?

I know I could wrap it around the stack, but I am not sure how that works with a float box and if I would get scorching.

I know also I could have a preheat pan sitting on top of my divided pan at the back, but my pan builder is not a big fan of those, although he said he would build it if I asked for it.

[berkshires]

I don’t have a steam hood and likely will not get one for the foreseeable future. Could I suspend the pipe just above the pan and get heat from the steam coming off the pan?

Yes, though you would get less efficiency for two reasons:
1 - Without the steam captured in a hood the temperature would be lower, so you'd get less heat to the pipe.
2 - A hood has channels running under all the pipes that capture the steam condensing on the pipe so it doesn't just rain back into your evaporator. Without these channels you'd have water dripping off your pipes back into the pan.

GO

[maple flats]

I used 4 copper manifolds, each was !" copper with 6 @1/2" take offs. The sap entered the hood at the rear of the, on the long side. Once inside it had a cap on the other end and each 1/2" take off got a 52" long copper pipe. That rose 1.5" above the entrance, then #2 manifold. At the opposite end from where it entered, I had an elbow and then a tee (1x1/4 threaded x 1). Then #3 manifold, ell on for end, then a 1x1/4 threaded reducer) The 6 5tubes then rose another 1.5" as they proceeded to over the first manifold. Then a 6" length of 1" copper got it out from under the hood. I used a 1.25" Greenlee punch to make those holes for into and out of the hood. My hood was 60" long. Once out from under the hood I had a length of 1" copper and an ell, so it extended about 3-4" post the float box entrance, then a 1x3/4" threaded x 1" tee, pointed down to a 1" tee, and ento feed the float box valve. The last tee had a 1" copper feed teed off the 1" infeed from the head tank, with a ball v. Doing that, if I ever needed to bypass the heater I could, the tubing into the heater also had a ball valve. In the 1/4" threaded fittings I put coin vents (used for venting hydronic baseboards or radiators) and the 3/4 " threaded was where I mounted my thermometer, with the 6"? probe surrounded with the heated sap. I also on the inlet, directly above the float box had a Tee, pointed down with a 1/2" ball vale for draining the preheater when the boil was done for the day. While I had the coin vents I never needed to vent any air in over 10 years of using the set up. My head tank bottom was 20" above the float box sap level and 10" above the inlet to the hood.
I bought the 4 manifolds from Ebay, the rest was locally sourced. Where the preheater lines entered and exited the hood I used a 1.25" Greenlee punch and the whole pre-heater sat on a drip tray, higher at the front, lower in the rear and the low end rested on the edge of the hood drain channel so condensation ran out the hood drain and not back into the flue pan.
Good luck!