Confused .... need an explanation

[devils11217]

Ok. I have a homemade 2 x 4 arch with a blower on it shooting air up to the fire. For years, I have ran the blower on with the natural draft door open. Tonight, I closed the door and left blower on. Similar to an air tight but by no means air tight on this thing. My Steam was half and I could see my syrup boiling. When I open the draft door with the blower on, everything gets so steamy I can’t see the boil. Close the door and steams goes away but boil is still raging. Someone explain.

[Cjadamec]

My bet is that you are burning hotter and better with the door closed. You should try it that way for a few hours and see if your evapration rate is better with the door closed rather than open.

If you are truly maintaining the same rapid boil the disappearance of the cloud like water vapor means your sap is boiling harder and the steam coming out is more energetic and hotter.

True steam is invisible.

Water vapor is what you see as the puffy cloud. It's what you get when steam looses it's energy.

[ecolbeck]

Perhaps its a weak blower

[maple flats]

It could be either but without more info my guess is with the blower, not big enough.

[minehart gap]

devil's, that kind of makes sense. From everything that I have read, you need to pick one. Either natural draft or air under fire. When you are running your blower and the draft door is closed, you are forcing the air to make the fire burn hotter but with the door open, some (if not most) of the air flow and/or pressure from the blower is lost to the draft door. The door is letting air out instead of your intention to have it bring more air in. If possible, measure the temperature of the stack at the base and see where you are in both scenarios. My bet is that the door open is cooler.

[Russell Lampron]

With the draft door closed you are getting a hotter fire which also means a better boil. The water vapor is there either way but with the draft door closed it's rising off of the pan hotter and condensing and turning to steam higher above the pan. Leave it closed and compare your evaporation rate. I think that you're going to find that it's better with the draft door closed.

[devils11217]

Thanks everyone. Always thought to keep the door open to allow more air to get fire hotter. I agree, my fire and evap rate seems to be hotter with the door closed. Stupid me always thought more steam visible meant better evap rate.