Neither the IRC nor NFPA 211 address the issue of multiple dampers in the same fireplace. Maybe that's because it is an uncommon occurance. Usually, you have one or the other. When a throat damper is replaced with a top damper, the throat damper valve plate and often the frame itself is removed to improve the aerodynamics for better flow. The main caveat in addition to those already listed is that the throat/damper/ smoke chamber cannot be less cross-sectional area than the flue. You need to remove the valve plate to route the stainless cable through the throat damper opening at the very least.

That's 8 inches--not feet above the Fp opening. :-)

FYI, a certain brand top damper made of cast aluminum shaped like a wedge is lovingly known as a "squirrel trap". When Rocky steps onto the damper, it falls open then snaps shut trapping him. Also, their 8x13 size is known to downsize the flue and cause smoking problems. Since the older designs do not have an integral cap, animals can still get in when left open as they often are. I recommend the newer combination rain cap/ animal guard/ damper in stainless steel. Several brands out there. All use a cable control in the firebox.

FYI, these dampers are not listed for use with factory built fireplaces. Their installation on a factory built fireplace voids the warranty and can burn the house down.

HTH,
nananananananananananananananana Hearthman!

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