Parallel Flow Preheater

[Brian Ryther]

After having my copper sepertine preheater sprung a few leaks this past season I decided to get rid of it an build a new SS parallel flow preheater. My question is.... do I need a vapor / expansion vent at the high point?
Brian

[maple flats]

I didn't and had no problems but it mightneed to be designed the same. The sap entered at the low end, the whole thing was tilted slightly sideways and the exit was on the oposite high side (diaganal corner. From there it was a straight drop into the float box. I do not know if any other way would work without locking with an air bubble. When I do my next one (before next season) I am putting a vent. Haven't decided if it will be a ball valve or just a vent like what I used for baseboard heaters. Called a coin vent, SS and screwed into a 1/8" pipe thread. I'm thinking a 1/2' ball valve might be easier and faster to use. I'm thinking it might be at the highest point directly over the float box.

[brookledge]

I'll say this. you will get some that say yes and some that say no.
Bottom line is the ones made by most manufactuers have vents on them. I would recommend that you just run a 1/2" line from the vent back to your feed tank. That way when you get a surge it won't get you.
On mine I actually just ran it straight up. Once and a while it will blow off a splash or two. If you are building one then I'd say include it now instead of having to add after. you can always put a plug in it until you see how it works.
Keith

[Fred Henderson]

Its a lot easyer to do it now than later which was my case. I ran straight up with 1/2" copper back to the feed tank. I took a chance without it and almost lost my rig the first time I ever used it.

[Brian Ryther]

Fred,
How did you almost lose your rig?

My old sepertine copper preheater did not have a vent and I never had a problem.

[Fred Henderson]

I lost sap flow and I attributed to vapor lock. Maybe be I was wrong but after I put the vent on I never had that problem again.

[Sugarmaker]

Vents....
I would be on the yes side of the room. I have three vents at the high end of a design very similar to Leaders parallel flow unit. They dump right back into the rear pan under the hood.

If all goes well I will not be needing the preheater next year and it may be for sale?

Regards,
Chris

[Maplebrook]

I built a parallel flow preheater last season and incorporated a vent into it. I put a tee in on the highest point. Threaded a nipple into the tee (this took it out through the top of the hood) and put a ball valve with a length of sap tubing to flow back to the float box. I'd open the valve often, but it seemed that most of the "bleeding" would be done in the first couple of hours then be done for the rest of the boil.

[vermaple]

I use a 1/2" pipe to vent my parallel flow preheater, the pipe extends about 6-8' above the top of the hood with a open ended cotainer on the top of the pipe. This container allows the burps to escape and the sap above the burp will return through the pipe into the preheater.