Preheater vent question

[NYScott]

I am a newbie setting up a 2x8, wood fired, raised flue, with a steam hood and preheater, actually I have two questions. First do I absolutely need a vent in my preheater, and if so what are some possible designs. Second if my sap storage tank is higher than 1 ft above the float box do I need a pressure regulator tank?

Thx

[Haynes Forest Products]

Absolutly...NO..... If you are taking the time to build a preheater and fabricate a shield and hood around a preheater Think ahead as you design it. A few more fittings wont kill the project so put them in. I have had several differant typs of preheaters and I had some vapor locking but not enough to shut mr down so I didnt change things. I also didnt have all the feedback that i found on this site so use the info wisely and learn from all our mistakes and tell us about yours. I think vents can also help in cleaning out the heater or for winterizing.

[NYScott]

Ok I think I have a workable solution I did put a vent in the header on the hot side of the preheater, however the vent which is 3/4" coppercomes up through the steam hood to a ball valve then reduces down to 1/4" soft copper that loops around and back down into the back pan. Then if I need it I can open it if I don't I can leave it closed. All I need to finish it is to rework the drain on the drip pan.

[WESTVIRGINIAMAPLER]

I have a 2x8 with a preheater I built and photos are in my weblink and I checked temp yesterday and it was staying around 170 to 175 degrees with damper 1/2 closed in the steam stack and I have no problem with vapor lock nor do I have it vent and sometimes it gets much hotter than that. My float system takes care of any vapor lock problems.

[Smitty]

Ok I think I have a workable solution I did put a vent in the header on the hot side of the preheater, however the vent which is 3/4" coppercomes up through the steam hood to a ball valve then reduces down to 1/4" soft copper that loops around and back down into the back pan. Then if I need it I can open it if I don't I can leave it closed. All I need to finish it is to rework the drain on the drip pan.
NYScott
My 1/4" vent runs straight up from the preheater, no vavle to open and close, up past the top of my storage tank. If i maintain agood fire, i get about 185/190 degrees. I do not
need to keep an eye on it, if it needs to vent, it just does. It laso lets air in when draining the system. It seems to work good.

[Maplewalnut]

Perfect topic. I filled my pans tonight and the floats worked perfectly, but then sap came shooting out the flexible copper I have in the preheater discharge and it would not stop until I shut off the feed tank valve. It is open on the end, do I nned to install a valve or just recycle it back into the feed tank? First time running this rig so I was not sure what to expect.

Maybe too much head pressure? I only have a 50 gallon feedtank maybe four feet higher than the preheater connected with 3/4 copper

thoughts?

[RileySugarbush]

You need to have the opening of the vent higher than the highest level of the feed tank.

[NYScott]

I do think that if you can vent your preheater and run the vent up higher than the top of your sap storage tank that would be the "Best" in my case that was not really possible for a couple of reasons

1.) My sap storage tank is actually in the hay maw of an adjoining old barn, I measured the difference in elevation last night and from the float pan to the bottom of the tank is 6.5 ft. (I can't get high enough in the sugar house to exceed this)
2.) I want to be able to winch my steam hood up and down. I need to do this to reverse the flow on this rig.
(I think the extra hose I would need to run the vent back up to the maw of this adjoining structure would be a pain and look like crap)
I did need to put in few extra valves to adjust flows if I end up with to much sap pressure on the float or if I am starving for sap due to vapor lock in the preheater. I don't really see what the big deal will be opening a valve on the preheater to relieve pressure and dump it back into the back pan. Yes this may be a bit of a "Rue Goldberg" setup. If it works and is not to much of a pain in the *** I'll leave it. Otherwise this summer a pressure regulator tank will go in 1 ft. above the float box and then the preheater vent will only need to be higher than that, about 3ft total.

I think my plumbing will be finished tonight. I'm hoping to fire up for the first time for a test run with water in the next few days. I'll let everyon know how it goes.

[Smitty]

NYScott,
Sounds like you are set up perfect for your application, good luck/have fun.

[Uncle Tucker]

I built a preheater this summer. I looked at the pictures on the UVM preheater efficiency paper and saw a little petcock valve that went into the flue pan. I used this idea and put the vent with a gate valve (easy to adjust) into the float pan. I tried it on a test boil and worked flawless. I just let the valve drip a little and the bubbles would rise up and out the valve. It might look a little mechanical but it beats running a line 8’ up to my feed tank. I have pictures in my signature.

[danno]

Hi Scott -

I had serious vapor lock issues last year - I put a T in my sap pipe before it enters the preheater and ran some pipe and T'd the pipe back into the sap line after the preheater just before it enters the float. I have a valve on this "by pass" line.

When I start vapor locking, I open the valve. This sends cold sap into the float box and also clears the vapor lock. I would have been in loads of trouble last year without the by pass line.

Only thing is I hate running cold sap into the flue pan, you can see an immediate reduction in the boil.

I also have a pressure valve in the pre heater, but could not get that to work right. Have to work on that this season. I'd much rather clear the lock by releasing the pressure as opposed to adding cold sap. But the by pass is darn good insurance.

[brookledge]

NYSCOTT
Why do you have to remove the hood to switch the flow? Seems like alot of work. Is the hood down tight on the syrup pans?
Keith

[NYScott]

On the "Small Bros." Lightning evap that I have you actually have to reach down into the back pan and swap a plug and a 4ft. tube from one side to the other each time you want to reverse the flow. I agree it is not ideal but the price was right when I bought it and I'm hoping if I set it up right it will not be that big of a pain.

[paul]

hey nyscott
we have two pipes and two plugs in our lighting,we have two access doors on the hood . just open door reach inside change the plugs and your ready to go. seems to work good for us