Preheater idea?

[sandman6921]

Has anyone tried to make a preheater utilizing some exhaust heat?
Thinking of adding a metal box adjacent to my stack, and regulating the amount of exhaust with a sliding baffle plate. The bottom of the "box" would have a couple drain holes to get rid of condensate. I was thinking about 25' of 3/8" soft copper just snaking around. Anyone ever tried anything like this?

[WESTVIRGINIAMAPLER]

Years ago I ran a piece of copper tubing through the firebox. It was the best preheater I've seen for the minimal cost. Sap always came out boiling hot and at end of day I dump about a quart of water through it to flush out any sap in it so it didn't scorch.

[Shaun]

I ran some 3/8 copper inside a homemade hood. I boiled about 15-17 GPH and would have the valve wide open when the tank got low and lost head pressure. It worked, 17 GPH is about all it would flow at times with 20 feet or so of tubing.

[sandman6921]

Just thought if I could get it out from under the steam hood, I wouldn't have to deal with the condensate