Let’s get technical. Today we’re talking BTU’s and what that really means when it comes to your gas fire pit.
British Thermal Units (or BTU’s) are described as a unit of energy required to heat one pound of water by one degree Fahrenheit.
But perhaps a more relevant description of BTU’s for a fire pit or outdoor decorative appliance is that the greater the BTU the more flame and the more heat the fire pit or appliance will generate. BTU output will generally range from 30,000 to 100,000 on a fire pit or outdoor decorative appliance. Therefore, the higher the BTU, the more warmth you will feel from the fire.
The flame appearance and height on a burner is affected by a number of things besides the BTU:
1. The amount of primary air mixed with the gas before it is burned will affect the overall color and flame height. The more primary air the bluer the flame color will become and the shorter the flame will be. It will also be a cleaner and higher temperature flame. More primary air is added by opening the air shutter* more at the orifice location. Less primary air is done by closing the air shutter. This causes a brighter yellow flame and a taller flame. But closed too much and you will have a sooty dirty flame. While cleaner than a wood fire it still can be dangerous due to CO2 generated.
2. Larger orifice hole means more BTU’s to the burner, assuming all else is the same.
3. Higher gas pressure means more BTU’s to the burner, again assuming all else is the same.
4. Natural gas (1000 BTU/ft3)has less BTU’s per cubic foot than LP (liquid propane)(2500 btu/ft3)
5. Natural gas typically is used at 3.5 to 7 inches of water column
6. LP is used typically at 10-11 inches of water column.
Natural gas and LP are sold by the BTU so the more BTU’s a burner uses per hour the more it will cost to burn the appliance. So all in all, while you generally want a high BTU measure for your gas fire pit or fireplace, other factors are also important to consider when purchasing the right fire pit for you!
*Not all outdoor gas burners utilize an air shutter. All Outdoor GreatRoom Company Crystal Fire Plus burners do.