Drop-flue air gap

[Jim Schumacher]

On a drop flue, how much air space should be between the bottom of the flues and the brick? Should the space be the same along the entire flue pan?

[RileySugarbush]

About half an inch for the full length. Just enough to get some flow under the flues and small enough to force most air by the big areas on the sides of the flues. Since the flues are open on both ends there is no need to have ramps or variations under them.

[WESTVIRGINIAMAPLER]

Most arches are designed by the manufactures so that a full size firebrick will go on the arch underneath the flue pan and the space is perfect unless you are using 1" rail gasket, you should be in good shape.

[Haynes Forest Products]

Quick way to get it close is play ground sand its bigger and will stay in place and its CHEAP.

[Fred Henderson]

I have 3 inches under mine. My drop flues are not open at both ends. Only the front is open and the back has a crossways flue connecting them all together.

[RileySugarbush]

Fred,

Do you have it built up close for most of the length and then dropping down to clear the back flue? That seems like it would work best.

[Fred Henderson]

Nope its 3 inches straight thru and I don't plan on changing it. It works super good. I fooled around with differnet heights when I put it in and the 3" space worked the best for me. I don't want all my heat up the stack. We all knock Patrick but he has a good design. He told me how to brick it up an he should know. Wood consumpution to gallons of syrup is at a good ratio. Please don't ask what it is, because it changes as the wood type changes.

[Jim Schumacher]

Thanks gentlemen. Next question. Is it necassary to insolate and brick under the grates of a forced air unit?