Match lit is not the only way to fire the ring

The match lit method of igniting a gas fire pit fire ring is just what it sounds like.  Strike a match (better to use the longer grill lighters to increase the distance between your hand the igniting flame) and turn on the gas.  As discussed in the last blog, there some drawbacks to a match lit gas fire pit.  The most important is the lack of a flame control failsafe.  If an unattended gas fire pit flame goes out, there is nothing to cut the gas flow.  Gas has not fulfilled its destiny until it becomes flame.  Therefore, gas will seek an ignition agent, like that cigarette in someone’s hand, to become greater than itself.

In its simplest form, a flame failsafe is a valve and a sensor.  The sensor tip sets in the burner flame giving assurance to the valve that the gas is, indeed, burning.  Should the flame go out, the sensor quickly cools and signals the valve, “Hey!  Got gas.  Don’t got flame.  Shut down.”

Match lit gas fire pits are just fine for residential applications.  People generally don’t light the fire pit unless they intend to enjoy the warm spectacle.  Come on.  We’re turning money into fire here.  My father would get on us kids for leaving the TV on when no one was in the room.  “The furniture doesn’t need to be entertained.”  Same idea.

Flame control for public applications is an absolute must for liability reasons.  The cost to a hotel, spa, or golf course to pay to station someone at the fire pit for the burn duration is much more than building the fire pit using a failsafe system.  Ignition is either by using a hand held remote control or a wall switch.  Remote controls tend to walk off by themselves.  A wall switch works much better for public uses.  Unless a fire pit is intended to be on all the time, I suggest adding a timer to the wall switch.  This will help keep costs of operating the fire pit down and diminish the need for constant surveillance by paid personnel.

The alternatives to the match lit system are: battery powered, push button grill, electronic ignition kits, and Crossfire.

Propane characteristics and cautions

Liquid propane (LP) is an excellent gas to fire your pit. Propane is trickier and more complex to handle than natural gas. Liquid propane is just that a liquid with a low boiling point. Liquid propane comes in different sized tanks. The tank is not completely filled. This is to allow the liquid propane room to boil off into gas. Larger tanks are able to boil off more liquid propane into gas and can, therefore, flow more propane gas. This is important to know when selecting the fire ring size for your pit. If the control valve flows more gas than the tank can process the tank will shut down to about 10% flow.

My thanks to Propane 101. Check out this website for much more information about propane.


SPECIAL ANNOUNCEMENT

I just heard last week of a propane fueled fire pit blowing up. Fire glass, the fire ring, and the pan were ejected out the top of the fire pit. Luckily, no one was injured. I have not heard of this happening before, but that is not to say it hasn't. As mentioned earlier, propane is heavier than natural gas. Somehow propane gas seeped down into the bottom of the pit and then ignited. It seems to me that the gas would have had to flow for a longer time than it normally takes to ignite the burner. Another possibility is that liquid propane got into the supply hose somehow. This condition will produce much more propane gas than what is produced in the tank. Now, this is only speculation on my part, but it does emphasize the fact that LP must be treated with caution and respect.

I would like to see your comments and experiences with fire pits, NG or LP, that have ignited in an uncommon way.

One other item, LP tends to cause soot as it burns. It is just not as clean burning as natural gas. An LP orifice added to the line to the burner introduces more air to the mixture going to the fire ring and helps to minimize this problem.

Next blog: Beautiful fire pit - Disappointing flame

Where to start when designing a gas fire pit

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?"