Multiple Dampers - InspectionNews

Michael Thomas · #1 (**permalink**) 02-18-2008, 08:33 AM

When a chimney top damper is installed, what modifications -if any - should be made to the original damper?

Rick Fifield · #2 (**permalink**) 02-18-2008, 11:12 AM

I like top dampers and have used several with spark arresters. The lower damper in these cases was never installed. The IRC only says to use a ferrous metal damper 8' min. above the lintel and be operable from the room containing the fireplace. No mention of quantity.

Rick

John Arnold · #3 (**permalink**) 02-18-2008, 11:53 AM

What we need with questions like this is a Batman-type signal that alerts Bob Harper. I'll bet he shows up here pretty soon, though.

Jerry Peck · #4 (**permalink**) 02-18-2008, 05:01 PM

Quote:

Originally Posted by Rick Fifield

The IRC only says to use a ferrous metal damper 8' min. above the lintel and be operable from the room containing the fireplace. No mention of quantity.

Rick

I believe the IRC uses the term "damper" which is singular.

Of course, though ...

R201.2 Interchangeability.

Words used in the present tense include the future; words in the masculine gender include the feminine and neuter; the singular number includes the plural and the plural, the singular.

I would think (which is frequently dangerous) ... that 'more than one damper' typically equates to 'smoke filled house'.

Bob Harper · #5 (**permalink**) 02-18-2008, 07:09 PM

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!

Jerry Peck · #6 (**permalink**) 02-18-2008, 07:15 PM

Quote:

Originally Posted by Bob Harper

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.

Bob,

as John said:

Quote:

Originally Posted by John Steinke

Let's face it: some things are so basic as to be self-evident, and one seldom sees a rule against them. For example, I'm pretty sure there's no law specifically against stepping in front of a speeding locomotive.

Bart Ogden · #7 (**permalink**) 02-24-2008, 09:35 AM

Actually, there is a way to have multiple dampers installed.

If someone drills a hole through the side of the damper frame, out of the travel path of the damper valve plate on a masonry fireplace, you can run the cable and cable protector through that area to enable both dampers to work.

This is beneficial if someone is attempting to trap the cold air column within the chimney.

Sometimes, when using only a top mounted damper, there is still a significant cold air effect present and shutting the primary damper will stop of slow down this effect.

Sincerely,
A. Bart Ogden, President
Home Safe Hearth & Chimney, Inc.
Wichita, KS
Voice 316-265-9828
Fax 316-265-9890
www.HomeSafeKS.com

Aaron Miller · #8 (**permalink**) 02-24-2008, 09:58 AM

Quote:

Actually, there is a way to have multiple dampers installed.

This is beneficial if someone is attempting to trap the cold air column within the chimney.

Sometimes, when using only a top mounted damper, there is still a significant cold air effect present and shutting the primary damper will stop of slow down this effect.

Is this a common practice? If so, on masonry or metal chimneys or both? Are there any studies or research to show its actual effectiveness?

Just Curious,

Aaron

Bart Ogden · #9 (**permalink**) 02-24-2008, 10:06 AM

Quote:

Originally Posted by Aaron Miller

Is this a common practice? If so, on masonry or metal chimneys or both? Are there any studies or research to show its actual effectiveness?

Just Curious,

Aaron

Not necessarily common, but it's done and it does help in certain cases.

Granted, this is typically a pressure issue. From what we've seen, it does tend to lessen the effect, though.

You wouldn't install a top mount damper on a factory-built fireplace. If the damper is inoperative or defective, you need to replace the fireplace unless the manufacturer has specific repair parts available.

Bart

Aaron Miller · #10 (**permalink**) 02-24-2008, 10:10 AM

Bart:

By the way, nice knotted chimney on your site . . .

Thanks,

Aaron

Bart Ogden · #11 (**permalink**) 02-24-2008, 10:12 AM

Thanks!

That's actually a chimney in Kansas City, about 3 hours from us. It's a fiberglass piece that is life-sized and there are all kinds of trumpets and instruments sticking out of it. It's located on a college campus near the music center. It's pretty cool!

Bart