Hood / Pre heater - how big of vent stack?

[BSD]

I'm having major ventilation issues in my new shack and have to build a hood to handle the vapor. Is there a general rule of thumb for sizing the vent stack for a hood?

My pans are 30x10'. currently boiling under 60 GPH, but hoping to go a bit faster when i build a hood and make a pre-heater. Can i get all the steam up a 12" stack?

[Potters3]

I have a 30"x 12' with 2 hoods each has a 12" stack on it from factory. Flue hood is down tight, we raise the syrup hood up a couple of feet so everyone can see in. No issues with steam and we are going at 175- 200 GPH

[Potters3]

Thats thru put running 10% sap, not just evaporation

[BSD]

I have a 30"x 12' with 2 hoods each has a 12" stack on it from factory. Flue hood is down tight, we raise the syrup hood up a couple of feet so everyone can see in. No issues with steam and we are going at 175- 200 GPHand that is with no mechanical fans, correct?

[BAP]

You don’t need fan to get steam out, the hood and pipe take it out by convection of hot air rises.

[BSD]

You don’t need fan to get steam out, the hood and pipe take it out by convection of hot air rises.I was pretty sure that was the case, this is all new territory for me, boiling indoors.

[BSD]

Thats thru put running 10% sap, not just evaporationso you're running much more concentrated sap, so there is significantly less water to make vapor, which brings me back to the original question, can i get by with a 12" vent or do i have to go up to 15/16"? I only have one open bay in the roof to run the vent.,

[maple flats]

I have a factory hood on my evaporator, the syrup hood is 3x3 and the flue pan hood is 3x5, each have a 15" stack. On average I boil 9-11%, but the manufacturer likely sized it for 2% sap. My stacks are bigger than most others in my size range. They work fine for sure. When I added the pre-heater in the flu pan hood, I closed the damper on that stack to just about half closed, it still works good. I closed the damper with a good boil in the pans and closed it until a little steam started to escape thru the loose fitting hood and I left it there. That was to hold the steam in contact with the pre-heater better.
If you vent with just 1 steam stack I'd suggest one stack of 16", but 14 might work ok. My stacks work well and they terminate in the cupola, do not go thru the roof. Our rigs are essentially the same, 24 SF vs 25 SF.

[Ghs57]

I put a home made hood on my 2x6 with an 8" vent. I'd go 10" if I were doing it again, or two 8", front and back sections. As it is, it removes about 90% (boiling raw sap).

[BSD]

My stacks work well and they terminate in the cupola, do not go thru the roof. Our rigs are essentially the same, 24 SF vs 25 SF. I've been having a hell of a time getting good ventilation. the decorative windows i put in my cupola are not big enough for my evaporator and i get a cloud layer at about 80" on a good day. high humidity days are downright dangerous to boil in. can't see anything, almost had a foam over because i couldn't see inside. I'm going to have to go through the roof i would think.

17768
17769

As far as design of the hood. would a 1x1x1" gutter be sufficient?

[ponderingjunkman]

I have a 30" by 8', with a 6 and an 8 inch steam stack in the hoods. Built a new flue pan for this season, and had a big vapor problem . Added an 8 by 16 inch duct-had some of that in the scrap pile- and no more vapor problem. But the preheater doesn't work as well. I'm gonna make some baffling to direct the vapor thru the preheater better, we will see

[Ghs57]

I've been having a hell of a time getting good ventilation. the decorative windows i put in my cupola are not big enough for my evaporator and i get a cloud layer at about 80" on a good day. high humidity days are downright dangerous to boil in. can't see anything, almost had a foam over because i couldn't see inside. I'm going to have to go through the roof i would think.

17768
17769

As far as design of the hood. would a 1x1x1" gutter be sufficient?

Boy, that looks familiar. First year with my 2x6, no hood. Had to run a fan in the upper window to try to draw out the steam. Didn't work so well.

[Haynes Forest Products]

Looks cozy warm to. Do you ware glasses??? YIKES No I don't recon you do, maybe some swim goggles.

[Potters3]

No fan and the first year we boiled raw sap with no problems. I can leave the door open on hood and there is enough draw up the pipe to keep the steam from coming out. I have 12 or 15' of stack on each hood and they are 3 or 4' above the peak of my roof to get good draft.