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About a year ago I replaced damper on my fireplace
and now it does not draw as well as it used to.
The original unit was a standard Heatilator manuf. fireplace (circa 1950) which had an integral flat damper that “hinged” on the smoke shelf and kept falling down. The chimney is a masonary with 12 inch tiles and drew well.
I replaced the damper with a chimney-top cable actuated unit made for 12 inch flue tile. When open, it definately is more restrictive (but not much – maybe 1 inch all around).
I removed the old damper completely and wonder if this was a mistake. Does anyone think that the original damper and (when open) its position in the chimney (and smoke shelf) aided the draw?
TomM
Replies
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Dear Tom,
Yes the flue is a bit more restricted with the new damper. Let's do the arithmetic.
You started with about 144 square inches and blocked 46 of them. That's about a third of the flue section and going to hurt.
Also, this may be the last straw in a compromised system. Houses of this vintage suffer from many unintentional chimneys that compete with your flue for draw. The chimney chase itself may be pumping indoor air into the attic causing low pressure inside. So take a look up there for some serious holes.
Cordially, Fred
*You don't say what is happening with the new damper. Are you getting smoke back into the house? Is it just hard to light? Just what is happening?As has been pointed out you have restricted the chimney. But, depending on what you are experiencing there may be a way of living with it rather than doing expensive repair work. Assuming inspection shows no holes or other hazards in the chimney.
*Tom, We had a nearly identical situation. The old Heatolatordamper had corroded badly, so we had it replaced with achimney-top damper. With either damper, however, a firewould almost always leave a smoky smell in the house. We paid a trip to a local fireplace store. The ownertold us that a lot of homes built in the 1950's ( likeours ) had a hearth opening which was TOO LARGE inproportion to the size of the chimney flue. He suggestedthat we reduce the effective size of the hearth openingby installing one more layer of firebrick on the floorof the hearth. After doing this, our problem was eliminated. I'm sure this problem is discussed in a technical booksomewhere, but I haven't come across it yet.
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Ed,
That's an interesting point. I assumed that since it was essentially a manufactured fireplace (except for the flue)
that it was dimensioned correctly for its flue - I'll check.
Yes, a smokey smell is the problem, not lighting or burning.
I wanted to remove the grate and build the fire on the floor (as I've read is prefered), but not after experiencing
the reduced draw.
FredL, yes I have probably 2 or 3 flues worth of leakage around the chimney - just haven't got up in the attic with
a roll of sheet metal to fix it.
Tom
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Don't know where you read that fire building on the floor was preferred. That definitely has not been my experience. Use a grate.
Seems to me that Ed is right on based on my experience. Same thing happens with air-tight wood stoves. They can't maintain a proper vent because the chimney is effectively too small. So, tighten up the leaks in the flue both for efficiency and fire protection. If that doesn't do it then reduce the size of the hearth opening. Can't remember the formula but Ed's idea of a layer of firebrick is probably a good place to start.
With the old damper you probably had just enough additional draw to not notice the problem.
*Tom, I forgot one other thing we did. We also purchased andinstalled an adjustable length panel which fits in atthe TOP opening of the hearth. I think the range ofadjustability is about 30 to 42 inches. This fits nicelyin our 36 inch wide hearth opening. It's spring-loaded,so it braces itself securely against the verticalsides of the hearth. The panel is 4 or 6 inches wide,and is brass in color. I think other colors are availablesuch as black, so that a person can choose a color whichfits nicely with the color or style of their fireplace. This panel ( at the top ) and the firebrick ( at thebottom ) effectively reduce the size of the hearth opening.
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About a year ago I replaced damper on my fireplace
and now it does not draw as well as it used to.
The original unit was a standard Heatilator manuf. fireplace (circa 1950) which had an integral flat damper that "hinged" on the smoke shelf and kept falling down. The chimney is a masonary with 12 inch tiles and drew well.
I replaced the damper with a chimney-top cable actuated unit made for 12 inch flue tile. When open, it definately is more restrictive (but not much - maybe 1 inch all around).
I removed the old damper completely and wonder if this was a mistake. Does anyone think that the original damper and (when open) its position in the chimney (and smoke shelf) aided the draw?
TomM