Mechanical troubles with fireplaces: fireplace doors
Fireplace Door Difficulties
A good set of fireplace doors is a highly- recommended accessory for saving heat and optimizing your enjoyment of the fireplace. But if the doors are damaged, improperly installed, or out of adjustment, they can be frustrating. Your chimney professional can fix most fireplace door problems.
But if you want to give it a try, here are some things to check.
Glass doors are breakable! Be careful, and wear appropriate eye and hand protection.
Adjusting fireplace doors
If the doors don't open and close smoothly, first check to see if there is an adjustment. Often, where the doors attach to the frame there is an adjustment that allows the top and/or the bottom of each door to be moved left or right, correcting a binding or poorly- operating door.
If there is no adjustment, or if there is not enough adjustment to completely solve the problem, the door frame may be improperly installed. If it is crooked, loose, or uneven, it could force the doors "out of square," making them operate poorly.
Most doors attach at the top by means of a clamp assembly. A thumb-screw tightens the clamp assembly to the lintel bar, the piece of angle-iron that holds the bricks up at the top of the fireplace opening. At the bottom, the doors are usually bolted into the inner hearth. Take a look, and you will see how this works.
If the doors seem crooked or loose, and if you are brave, you can try adjusting the clamps. But have somebody else on hand to steady the door before you adjust anything, or the door could fall.
If the door frame itself is badly worn or warped, you will probably need a new set of doors.
Fireplace doors incorporate tempered glass that's designed to withstand heat – to a point. With better-quality doors, you can operate the fireplace with the doors open or closed. But some things can cause breakage.
You can save yourself from the rather startling experience of a exploding glass door by knowing a little bit about different types of doors and their appropriate use.
Things to avoid doing, since they could break your fireplace door glass
Over-firing the fireplace
Using doors with thin, low-quality glass
Placing the grate closer than 6 inches from the doors
Slamming a log or fireplace tool into the doors
For two-sided fireplaces, operating the fireplace with the doors open on one side and closed on the opposite side.
The easiest way to break glass doors is to over-fire the fireplace. Burning pizza boxes, big stacks of dry pine, etc. (things that also pose a serious fire hazard) could cause thermal shock breakage. Tempered glass can withstand very high temperatures if heated and cooled slowly. But a rapid change in temperature causes thermal shock, rapid expansion or contraction, often resulting in damage.
If you plunge a hot drinking glass into a sink full of cold water, the glass will break. That's thermal shock. And it can happen to fireplace doors, too.
As you might assume, thin glass doors are much more susceptible to breakage than thick ones. Better-quality doors use glass roughly 3/16" thick or thicker. Some come with a lifetime warranty against breakage.
Keep the fire several inches back from the doors, to reduce thermal shock. At least six inches between the inside of the doors and the fireplace grate is a good idea.
Don't try this at home
As a demonstration, some sales reps will smack a door on the showroom floor with a poker. It shows that thick tempered glass doors can withstand a lot of abuse. But obviously, if you hit the glass hard enough, it will break. So don't slam logs or tools into your doors, especially if the glass is the thinner kind.
Finally, if you have a two-sided fireplace (one with two openings), and you have glass doors, you must operate the fireplace with both doors open or with both doors closed. (And if the doors aren't good quality, keep both open). Operating a two-sided fireplace with one set open and one closed causes extreme heat against the closed set, which could break the glass.
Warped or damaged screens
Sliding-mesh screens will eventually warp from heat, but can be replaced easily and inexpensively. Measure the height and width of the actual mesh (not the fireplace opening), and buy a replacement mesh from your local stove shop. If you are not sure how to remove the old mesh and install the new one, have your chimney professional do the job for you.
If you have a standing or gate-style screen and the frame is okay, but the screen is in bad shape, you can probably have the screen replaced also, but in some cases it is less expensive to buy a new screen. Ask at your local stove shop for more information.
Missing, damaged, or inoperable ash pit door
Some masonry fireplaces have an ash pit door, a small door in the bottom of the firebox that leads to an ash pit under the fireplace. If the door is missing or damaged, replace it. Usually the door simply lifts out. Bring what's left of the old one (or very accurate measurements of the hole size) to your local stove shop and buy another one.
If the door is there, but rusted shut, try some penetrating oil first. You might want to take the door out and fix it in your workshop.