Build a fire pit (firepit)
It is my experience that many people building gas (natural gas NG or liquid propane LP) fire pits start at the end of the process and work backwards and are often disappointed with the results. Fire pit design must start with the fire ring (the burner). The final size and height of the pit depends on the proper selection of this one component. Fire rings generally come in 6 inch increments starting at 6 inches up to 48 inches. Burners are custom made above 48 inches. The rings are made of either black iron or stainless steel. Black iron is more susceptible to corrosion than stainless steel, but should still be serviceable for 2 to 4 years depending on the climate. Compare Seattle, Washington to Flagstaff, Arizona, for instance.
First Rule: The bigger the fire ring the shorter the flame at the same gas pressure. An 18 inch ring will have a 22-24 inch flame at 150,000 BTU at the pit. A 24 inch ring will produce a flame about 18 inches tall at the same pressure.
The fire ring affects the design of the pit because of space and offset distance requirements. More about this later in a separate blog entry.
Next blog "Got gas?"
8 comments:
it's amazing to me how little information is on the internet concerning specific considerations when creating a propane fire pit (btu, ring size, tank size, etc.)so thank you for sharing your knowledge! I wondered if it is highly discouraged to create a ring of your own? i want to build a portable fire pit that will only be used for 3 nights.
Thank you for your question, Wendy. The time and effort building your own burner is worth more than one you can buy. Normally, I suggest using a stainless steel fire ring because it will last so much longer. In this case, an iron burner ring will do the trick. FirePitOutfitter.com calls such burner rings, CRS, and are as low as $26.
I hope you can solve my problem with a new 12 inch ring connected to a propane line that shares a regulator with a couple of other appliances. The flame goes out when the ring is buried under one inch of glass or small lava stone. When I open the valve for more gas pressure the unit shuts down. I was told that the unit has a pressure safety device. The flame is very yellow and gives off soot. What do you think the problem is? This is a new electronic ignition kit. thanks.
There are several causes for the electronic ignition kit to shut down. The first (and most overlooked) is the size of the LP tank. See the Nov. 11 article. For instance, a 20lb tank can flow a maximum of 80k BTU. Opening a line allowing greater flow than that will cause the tank to shut down. A 12" ignition kit will flow 90k BTU just by itself.
The popularity of glass in the fire pit has caused problems for some of the older ignition systems. Glass compacts more tightly than lava rock and affects burner gas flow, and glass on or near the sensor assembly (sets under a cage on the outer ring) disrupts airflow. Insufficient pilot assembly airflow will cause the sensor to shut down the valve. Just enough glass or lava rock to cover the fire ring is plenty. More than that will interfere with gas flowing from the burner.
Ventilation is the next concern. There is heat transfer between the burner and the valve box in the fire ring style ignition kits. The valve box is sensitive and will shut down if it overheats. One warranty in particular for a 12" ignition kit calls for (2) 9 square inch ventilation ports in the bottom of the fire pit. This is to allow cooler air in through the bottom of the pit.
In answer to your question, you have 4 possible causes why your ignition kit shuts down.
1. Gas flow exceeds tank capacity
2. Glass obstructs pilot assembly
3. Glass obstructs flow thru burner
4. Ventilation
I have 2 articles upcoming to discuss ignition kits and for a new product on the market, the Crossfire. After that, I plan a chart comparing the manual ignition system, the electronic ignition kit, and the Crossfire characteristics, advantages and disadvantages.
Thanks Adrian. Your comments were very helpful.
I hope someone can help, I didn't really plan this out as well as I should have. I am trying to use a 30" triple burner ring hooked to a standard LP BBQ tank and regulator. I can only get a measly 3 inch orange flame out of a few of the holes on the burner and the slightest breeze will blow it out. What did I do wrong?
Kyle, sorry to be away for so long. I'm in the process of turning this into a real website. Articles will be much easier to find.
The problem with your set up is that the propane tank cannot convert liquid propane into propane gas fast enough to adequately supply the 30" burner. A 30" burner will produce a 14" flame if provided with 150k BTU. A 20 gallon LP tank (the same size used for outdoor grills) can flow a maximum of 80k BTU. The BTU to the burner greatly affects flame height but is not a direct ratio.
The fire ring should be mounted 4" or more from the top edge of the fire pit to help protect the flame from wind.
What happened to the next blog?
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