Too Much preheater ??

[windyacres]

I am having a preheater built for a 3x10. It consists of 80 feet 3/4 thin wall stainless in parallel. what if any are the dangers of bringing sap up to the boiling point. could I be into vapour lock and end up starving the boiling pan. I hope to get about 75-80 imperial gallons/hour. I ,m thinkin that the preheater is considerably oversized ??

[BreezyHill]

Steam away brings sap to high enough to evaporate off water vapor.

Vapor lock depends on the design and if you have a place for the vapor to relocate and escape rather than going back to the feeder tank.

8' of SS 1.5" dairy milk line brings 40 gallon/ hr to 170-180 on average for me. I have had a bubble go up my tank level tube from time to time. That's why the tubing is sloped back to that point and the tube was extended past the feeder tanks top.

Ben

[steam maker]

The preheater i had the cold sap came in the back and traveled to the front then out the bottom of the front header back to floatbox , in the middle of front header on the top looking towards roof of shack there was a half inch stub stickin up that was the vent we ran that up to rafters then back to feed tank . If u were running hard then float shut it would bubble out and sometimes shoot sap into tank , never had it vapor lock , would rather have that line than be burning back pan

[StayinLowTech]

In my understanding, on any preheater there should be a vent to release any potential vapor lock. This would be a small tube starting at the highest point on the preheater runs where vapor would be trapped. The tube would be open at the end and rise to a level above the highest point of the sap in the feed tank. Good luck in Huntsville (I used to live in Sprucedale).

[maple flats]

I hope it's not too much. I'm in the middle of building a pre-heater. It consists of 4 1" manifolds each with 6 nipples off of 1/2". I am making it 52" long, 2 tiers. It will have 12 lengths of 1/2" copper each 46" long. It is being designed with the inlet low, sap enters the first manifold, slopes up to the other end to the second manifold, then rises to the third manifold and then rises to the forth manifold. From there it exits the hood and rises a little more to the drop into the sap float box. Just before the drop to the float box, I have a tee with an upright leg and a vent. At first that will be a ball valve, but if needed I can extend it up and over to the head tank just outside or I could put an automatic can vent if I can find one in SS. I wouldn't trust a hydronic heating can vent to be lead free. It will have just over 52' of tubing counting the manifolds, nipples and the 46" tubes. The top of the rise to the upper tier also has a coin vent on each end of the manifold.

[wiam]

Agree with make sure there is a vent. Also make sure the vented sap has a place to go. On my 2x6 the vent would blow out small amounts of very hot sap. The top of my vent hose dumped into a 5 gallon jug in the rafters.

[windyacres]

Thanks ; for the prompt replies, it is clear that I need good venting higher than head tank. we are putting a tee with a thermometer on outlet to float to moniter tempsis it possible to get sap out of heater right at the boil ?

[Sugarmaker]

Thanks ; for the prompt replies, it is clear that I need good venting higher than head tank. we are putting a tee with a thermometer on outlet to float to moniter tempsis it possible to get sap out of heater right at the boil ?

I have an opinion on this too.:) We have been running a preheater on a drop flue pan and now have moved it above the steam away.
This is a parallel flow type. sap enters the bottom manifold. Is pushed towards the elevated manifold end as it is heated. T the upper end we have three small vents the type the is used to connect your refrig ice maker to a water line. They puncture the copper to make the vent and can be opened or shut off as needed too. Also a short piece of hose is attached.
This hose just runs into the rear pan at a trickle. I keep all this under the hood and dont have to worry about hot sap exposure.
Don't forget to have some way to drain the bottom of the preheater. You don't want it to be full of sap and freeze and break.
FYI you probably wont get much more that 190 F from the preheater. It will not boil in the preheater but can get hot enough to cause these pesky air locks just when you least expect it.
Regards,
Chris

[johnallin]

I too am in the middle of finishing plumbing in a new stainless preheater. In my case, the bottom of the feed tank is about 6" higher than the lower manifold on the heater and I was concerned about having enough head pressure to push sap through the unit. With a T fitting I can feed the preheater directly, when I have enough head pressure. When the tank gets down to the last 15-20 gal, I will open a stainless ball valve, bypassing the heater and running cold sap directly into the float box. I should also be able to drain preheater and feed lines by pulling the bypass hose off the regulator and dumping into a bucket(s). The preheater sits on rails in the hood, and can be separated from the arch by use of sanitary clamps allowing me to raise the hood and heater together to access the flue pan. I will post more pictures as I go.

1304213043

[jimsudz]

Your preheater looks similar to mine.Never to much preheater. My vent tube is just a 1/8 inch copper tube that extends above the feed tank in the stack of the hood. I just curled the end back down so if there is sap released it will fall back into the drip tray. Ihave never looked to see if it ever spews sap. Ill lift the stack some time to watch for sap.

[johnallin]

They are very similar. What kind of sap temps do you get out of yours? For 6 years now, I've been averaging in the 30 GPH range on my patriot 2x6. I hope this gives me a notable boost in evaporation rate and a decrease in wood use.

[mellondome]

If you use a larger vent pipe, you don't have to worry about sap going out the top. I had issues with mine originally it was 3/8 tubing. Air would push sap over the top all the time. It is now 3/4 pipe to the rafters with a 1 in cap sitting loosely on top. No more issues. More than enough space for the air to bypass the sap.

[johnallin]

That's a great idea and makes a lot of sense.

[jimsudz]

Johnallin,I will get temps of 185-190*,once I put a damper in the steam stack. before the damper 160-175*,and a lot of fluctuation.A couple of years ago I did have a vapor lock. My feed tank was low and I lost my sap feed. The Gov suggested that I raise the vented side up a little Higher,and no issues since.

[johnallin]

Jimsudz, thanks. I had a damper put in the hood when I ordered it 2 years ago.
I will be experimenting with it. 195* sounds great to me, I can only hope to see those temps.
10-4 on the Gov.

[Sugarmaker]

Wow! Both those preheaters looks awesome! You guys are doing some great work! Those should help get that cold sap up to near boiling temps.
Regards,
Chris

[johnallin]

Chris, Thanks, but I can't take credit for the build. My preheater was made by Leader, I'm just setting it up...Welding is not my thing, wood is a different story.