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How to Install a Chimney Flue Damper

Posted by Jim Hessenauer on

7 Easy Steps to Drastically Improve Efficiency In Your Home

Stop your drafty chimney from stealing perfectly good indoor air. Heating and cooling gets expensive; a top lock chimney damper can pay for itself in no time. Installing a lock top chimney damper can be a great way to prevent any energy leakage from your home caused by a chimney. Open chimneys can be a major factor in losing heat in the winter and air conditioning in the summer. Even if you currently have a throat damper in your chimney, which many homes do, it still leaks energy. Throat dampers do not have a gasket and thus never make a tight seal. This means no matter what you do the damper can never be 100% closed and as it rusts and ages the gaps only grow. . A lock top chimney damper has a silicone gasket at the top of the flue to ensure an air tight seal every time. Lock top chimney dampers also act as a rain cap, keeping rain and critters out of your chimney. Lock top chimney dampers are extremely economical and are designed for any do-it-yourself homeowner to install. IF YOU ARE NOT COMFORTABLE WORKING UP ON YOUR ROOF PLEASE CONTACT A PRO.

With help from the following steps you can seal off your chimney today. You can find all our DAMPERS HERE

Warning: Top lock chimney dampers should not be used with gas log fireplaces.

Step 1: Tools

When you purchase a top lock chimney damper, it comes with 32' wire cable, allen wrench, 2 anchor nails, mounting bracket, and tube of silicone cement. The tools you will need are a drill with 1/4" masonry drill bit, hammer, wire snips, wire brush, and a sturdy ladder. Depending on how long you've been using the chimney, its last cleaning, and what you're burning you might also want a bottle of Brick Masonry & Stone Cleaner.

top lock chimney flue damper

Step 2: Assembly

Find the safety device wire located under the damper lid. Find the spring-loaded connecting tube with jam nut, cable, and handle in the hardware bag. Find the leg connector wire with fusible link in the bag. Remove dome nut from the end of connecting tube,and assemble chimney fire safety device as shown.  The chimney fire safety device must be installed for the warranty to be in effect.

top lock chimney damper safety device

Insert threaded end of conduit tube into underside of damper lid. Position safety device wire corner-to-corner and re-tighten dome nut onto end of bolt. Turn jam
nut an additional 1⁄4 turn with wrench to secure.

Step 3: Clean and Apply Silicone to Chimney Flue

Once you've firmly established your footing on the roof you'll need to clean off the top of the chimney flue. Brush off any debris and buildup to allow the damper to sit flush on the top of the chimney flue. If the crown/flue is particularly dirty, clean the area with Brick Masonry & Stone Cleaner. Next puncture the tube of silicone with the cap, and spread a 1/4" bead of silicone around the top of the chimney flue.

Step 4: Place Damper On Chimney Flue

Pro Tip: Uncoil the wire that comes with the damper ahead of time. After it's had some time to relax coil it back up in a loose roll and use tape or twist ties to keep it together. This will prevent it from running everywhere up on the roof. Once you uncoil the wire again on the roof avoid walking until you've lowered the wire to avoid tripping.

First Lower the wire cable into the chimney. Make sure that the cable does not kink and get tangled while being inserting down the flue. I recommend taping something to the end to add weight and then slowly feed the wire down. Then place the chimney damper on the top of the silicone bead on the flue. Make sure that the damper is centered on the flue and the entire flue is covered by the damper and then press down firmly around the edges. Fill any gaps with adhesive to ensure a proper seal. Allow adhesive to set 24 hours before using damper. (If using a Sweep’s Ring, sold separately, apply the ring to the adhesive and screw damper to ring.)

Step 5: Mount Bracket In The Fire Box

Measure roughly 20" from the floor of the fire box, and mark where the two holes of the mounting bracket are going to be on the wall of the fire box. Take your drill and 1/4" masonry drill bit and pre-drill 2 holes on the wall of the firebox for the anchor nails. Take the 2 anchor nails and place them through the mounting bracket in the pre-drilled holes you made in the fire box. Then, take the hammer and drive them in.

Step 6: Set The Adjustment Clamp

Thread the chain handle and cable through the mounting bracket. Locate the brass adjustment clamp. With the allen wrench, loosen the adjustment clamp. Pull the slack through the adjustment clamp, then pull the cable until the damper is fully closed. Position the adjustment clamp under the mounting bracket and with the allen wrench tighten the clamp until it is firm. Take your wire cutters and snip and discard the excess cable. Pull the cable tight and secure the chain under the mounting clamp.

Step 7: Victory!

Congratulations, you have successfully installed a Lock-Top chimney damper. Simply pull the chain away from the adjustment clamp and the damper will open when you are ready to have a fire. You are now free from losing energy, at least where your chimney is concerned.

chimney flue damper open positionchimney flue damper closed






Warning: Lock top chimney dampers should not be used with gas log fireplaces due to the dangers of starting the fireplace and forgetting to open the damper. 


Do you have a cap mounted damper at your house? What steps do you take to remember to close the damper after use?

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