Yes! Fire pit burner pans will expand when they get hot. It’s important to allow enough room in your fire pit tabletop to accommodate this expansion.
How Much Does a Fire Pit Burner Pan Expand?
Fire pit burner pans expand very little, but if you don’t allow room for any movement, the result can be significant.
Let’s take a look at the example of a 48-inch linear burner pan. To avoid using complicated formulas, we’ll use an online linear thermal expansion calculator provided by the good folks at The Engineering Toolbox.
Using the thermal expansion factor for 304 stainless steel, which is 0.000017, and a temperature range from 32 degrees F to 400 degrees F, we find that the 48-inch burner pan can expand by as much as 0.3 inches.
This is an exaggerated example because the maximum temperature and the size of the pan affect the result. In most instances, your burner pan will likely be shorter and won’t get near the 400-degree mark we used. But the example does show that even if your pan reached the max, the 0.
What Would Happen if I Didn’t Leave Room for Expansion of My Burner Pan?
If you don’t leave enough room for expansion in the cutout for your burner pan, it will expand in the only direction it can – upwards, in the middle. That will cause the pan to buckle.
Even a small amount of expansion can cause a significant buckle in the burner pan if there is no wiggle room. Love digging into the math? Check out the infographic below to see Pythagorean’s theorem at work.
How Much Room Should I Leave for Expansion?
The Pythagorean theorem is named after Pythagoras, a Greek philosopher born in 570 BC. However, many modern scholars believe it may have been around long before he was born.
We recommend that you make the cutout 0.5 inches larger than your burner pan. So, if the base of your pan (the portion that sits below the surface) is 6 inches x 18 inches, then your cut-out should be 6.5 inches by 18.5. inches. This will allow for .25 inches on each side for expansion, while still providing good support under the lip of the burner pan.
With smaller burner pans, you can reduce the cutout size from 0.5 inches to .25 inches larger than the burn pan because thermal expansion will be less.
A larger space is also more forgiving if your cutout isn’t perfectly square, or the edges are not perfectly straight.
Can I Limit Heat Expansion of My Gas Fire Pit Burner?
In a controlled environment, your burner pan won’t expand at all. This is because the heat from the flame is directed upwards.
When we demonstrate our burner pans inside our warehouse, the pans themselves don’t heat up. This is because there is nothing moving the flame. When there is a breeze, as you would have outdoors, the flame dances across the surface of the fire glass and comes in contact with the edges of the pan causing them to heat up.
One way to keep the flame centered in the burner pan is to use a glass wind guard. Also, if you have the option to locate your fire pit in a place with minimal wind, that will also help.
Another factor that affects heat is the amount of fire glass you use inside the burner pan. There should be just enough fire glass (about 0.5 inches) to cover the burner so it isn’t visible. Too much fire glass spreads the gas over a larger area causing the edges of the pan to heat up.
Decide to Expand
Your gas fire pit burner pan will expand and contract with heating and cooling. The expansion will likely be significantly less than 0.5 inches. Still, if you make no allowance for this change, even a small expansion could cause your pan to buckle.
Luckily, this can easily be avoided by simply making the cutout 0.5 inches larger than the burner pan base.