Steam hood and preheater, design and efficiency? A&A Evaporators?

[buck3m]

I've got an A&A 2x8 drop flue evaporator and am very pleased with it. It's "off the grid" so I don't have forced air, or an airtight door or anything fancy. It does about 38 gph, more if I push it.

I'm thinking about getting a steam hood and preheater. I boil in an A-frame. Under some conditions it gets very steamy in there.

I'm wondering the following:
What kind of efficiency increase can I expect with a preheater?
Would the hood just cover the flue pan, or both pans?
How high would the hood rise over the evaporator?
How high would my feed tank have to be above the current float-box to work with the preheater?

Thanks!

[Ghs57]

Speaking only of my home built equipment, I have no manufacturer's specs on the efficiency of my components. But there is undoubtedly a difference in all areas. 90% of the steam goes up the steam flue, so no more rain in the sap house. The hood encloses the flue section of the pan, and extends over the syrup section at a height of about 16-18" above the rim. The hood is about 24" high above the rim. The steam exits through an 8" duct through the roof. The preheater has 10 - 80" cooper loops (40" down, 40" back) through the flue section of the hood. My feed tank is about 6" higher than the preheater outlet. Sap enters the preheater at the outdoor temp, which is usually around 40 degrees, and exits at 100 to 150 degrees higher (I got different readings when I checked it). There is definitely some steam coming out of the float valve. With such heated sap entering the flue pan, there is not a very noticeable diminishment of the boil at the entrance point.

So, you will see an increase. How much depends on the equipment and your firing technique.