Add A Chimney Damper To Flue In A Custom Fireplace.

by grillrepair on

The Damper in a chimney is like a door that opens and closes to allow more or less air to be pulled out of the chimney.  When lighting the fire we will usually leave the damper wide open because the flow of oxygen feeds the flames.  However, once the fire is roaring we will often lower the damper so all the heat does not get sucked up the chimney.  We leave the damper partially open in order to coax the smoke out of the fireplace while still holding it closed enough that heat comes into the room.

In a standard fireplace the chimney has a metal tube running up through the wall, stacked brick, chase pipe, etc.  This metal tube is the flue and it is attached and sealed to the top of the firebox.  The flue is double or triple walled so the inner tube pulls hot air out of the fireplace and the suction of the hot air causes the outer layer to pull-in cooler air at the roof where the flue chambers are open.

The damper is built into the fire box and is a part of the fireplace before the flue or the chimney is added.  There is usually a handle in the front of the fireplace at the top of the fireplace opening and this handle turns to allow the flue to open and close.

What happens of a masonry fireplace is custom designed instead of using a pre-fabricated firebox and flue?   Using the pre0fabricated firebox and flue is easier and safer because the specification that allow venting and insulation to correspond with building codes are already built into the size and design of the firebox.   Sometimes a home has a fireplace that is totally custom and the chimney built from actual bricks or covered with brick over a metal flue that is not part of the fireplace box.  When the steel damper door rusts out we have to replace it but getting inside the flue — a custom flue or a pre-fab flue — is almost impossible.

In order to add a damper that allows us to control the fireplace chimney pull and direct heat into the house and smoke out of the house we add the damper at the termination cap at the roof.

install a new fireplace damper door at the termination cap

Install the damper under the termination cap of the chimney

We will have a square or a round opening under the termination cap on the roof.  Remove the termination and clean the area so there is no damp areas.  Install the damper door assembly si the sable drops into the flue and the high-side of the damper is higher towards the most common wind.  Make sure the 4 inch spring hangs freely from the lid when the damper is closed.

Use the adhesive that comes with the lyemance damper kit so the adhesive is covering the edge of the flue opening where the damper will mount.  This adhesive is designed to withstand outside weather extremes, heat, cinders, constant wind and moisture — it is very damgerous so do not touch it.

Install damper under termination cap using included adhesive

Notice the damper needs to be installed so high side of damper is against prevailing wind.

Press the damper into the adhesive and allow the assembly to sit and harden for 24 hours.

Now there is a door that will totally seal-off the pull of the fireplace flue.  The design of the chimney causes a “pull” of pressure from the fireplace to the roof so smoke is naturally pulled out of the fireplace.

Often a damper is added to a fireplace that is not used often because the pull of the fireplace is able to emit central heat and central air conditioning which causes a huge loss of climate control and higher energy costs when the home interior climate controls are sucked out through the chimney.  In order to test the fireplace sit right in front of the fireplace opening.  Light a candle and then blow it out.  Watch the smoke coming off the candle wick.  When the flue is working properly we will be able to see the smoke from the candle being pulled into the fireplace and then up the chimney.

install the handle and bracket inside the fireplace opening.

install the handle and bracket inside the fireplace opening.

Inside the fireplace the fire box liner is usually a fire brick panel or stacked fire brick.  In order to withstand fireplace heat fire brick and mortar cannot have any air or water bubbles in the brick or mortar mix.  Air or water that expands from heat while stuck inside a solid material will cause the brick to explode.  For this reason fire brick is very dense and heavy.

Use a 1/4 inch masonry drill bit to tap installation holes for the L shaped bracket.  Drill nice and slow through the dense firebrick about one inch.  Plan to install the handle bracket about 20 inches from the floor of the fireplace so there is room for the handle to hang and be pulled down.

Always wear protective materials when using power tools.

Using the first hole drilled, place the bracket in place and hammer a nail into the firebrick to hold the bracket to the fireplace wall and then drill the second hole and nail it in place.

Install chain and handle and adjust the lock so handle pulls damper open and releases to close.

Install chain and handle and adjust the lock so handle pulls damper open and releases to close.

Install the pull handle which will either be a simple chain on a pull or an angled mechanism to pivot when pulling.

Adjust the brass lug on the chain mechanism by pulling the cable down until damper closes and a slight spring tension can be felt.  Tighten the brass lug above the bracket hole and tighten to the handle.

Once the handle is attached and firm and is opening and closing the damper easily get back on the roof and check that the damper is tightly sealed.  Reattach the termination cap tightly.  Cut away any excess cable so the cable is tight as it runs down the chimney.

Damper installation with pivoting handle to pull chain

This wood burning fireplace has a chimney damper at the termination cap.



This image shows a wood burning fireplace that is on the ocean so the original damper rusted and needed to be replaced.  Instead of a handle that locks to an L shaped bracket we install a bar that limits the up and down movement and makes the movement easier to move also.  Moreover this type if installation allows the handle to be stopped at six different spaces so the flue is not only opened or closed.  The damper can be partially opened and left in that position so smoke and fumes are emitted from the chimney but heat is pushed into the room.

Contact Majestic Grill Parts for assistance anytime.


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