How to use a damper / flue

Hi all,
I'm in a home with a fireplace for the first time and I noticed that the flue lever has notches cut into it that would allow it to be partially open. It would seem to me that a flue should always be completely open when the fireplace is in use and completely closed when it is not, but it would appear there is something I'm missing.
I've seen this on other flue levers as well. Is there a better way to use a flue when operating a fireplace?
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It probably depends on whether the fireplace has glass doors. If yes, the experienced user may be able to fine-tune the rate of burning by adjusting the door dampers (allowing oxygen in to the fire) and the flue damper (allowing smoke and hot air up the chimney.) Without doors, probably no one can thus adjust the rate of a fire's burning.
--
Don Phillipson
(stove user, for heat, nor decoration)
  Click to see the full signature.
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The optimum opening for is a flue is as small as needed to prevent smoking. Anything larger just causes a loss of heated air.

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Thank you TH and Don for your answers. I just want to post one more that was emailed to me from Robert which agree with yours. His answer was pretty detailed and is probably very good advice.
* * * * * * * *
When you first start a fire in the FP, you will need to have the flue open all the way. Once the chimney and flue have heated up and natural convection begins to take over, you can close down the damper as much as possible. Keep closing it more and more until it begins to allow smoke into the room, then open it back up just a bit.
A fireplace is a really bad way to heat a room due to the fact that a tremendous amount of air is drawn out through the flue and this creates a negative pressure in the house. This draws in cold air from outside wherever it can get in. Therefore, closing the damper down, limits the amount of air drawn out and conversely the amount drawn in.
In addition, it helps to have doors on the fireplace that you can close. This further limits the air drawn out.
In addition to the airflow drawing in cold air, the rapid flow of air over the wood acts like a bellows and causes the wood to burn even faster. So you use more wood and stay colder, unless you close down the damper.
NOTE: Badly designed fireplaces may HAVE to have the damper open completely or they will smoke up the house. You will have to determine whether you have a good one or not and whether or not you can close down your damper.
-- Robert Allison Rimshot, Inc. Georgetown, TX
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"trbo20" wrote

Good answers all of them. I'll add one thing you probably thought of but no one pointed out. Once the fire is going, the flue handle is burning hot. I had an old 'adjuster tool' to adjust mine but the renters disappeared it.
It was sort of like a walking cane with an almost flat but slightly u shaped (upwards u) 'handle'. This let me scale the flue back and forth as needed a bit.
For now, we build to the back of the fireplace, and are at 3/4 'throttle' which is perfect for our draft.
Be sure to have it professionally cleaned annually if you are going to actually use it. It's also cheaper to have it cleaned in late spring or summer with a regular annual contract. Also be sure the chimney cap is the kind that bolts on. The cheaper ones that stay on by mere 'tension' dont work very well if your area is windy at all. Me, we get hurricanes here. Renters let one blow off and left it off all summer. Short version: 1725$ worth of water damage and we were lucky to get back before the first freeze or it would have been *much* worse.
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