Gas Grill Ignition Systems

October 17, 2013
There have been several attempts through out the history of gas grill manufacturing to produce a reliable automatic ignition system.  Starting out with the simple Piezo Electric igniters and concluding with Hot Surface igniters.  In this article, we will take a look at the pros and cons of each system and what can go wrong to make them stop working.

The majority of ignition systems on grills work using a spark to ignite the gas coming from the burner in order to light the burner.  The necessary components are a "spark" generator, wiring to carry the spark, and an electrode that allows the spark to "jump" from the tip of the electrode to a ground point. How easily the grill lights and how long the ignitiion system lasts depends on how good all three of these components are.

Piezo Electric ignition systems were the industries first attempt to produce an automatic ignition system.  Piezo Electric spark generators are still in use, but they are not the best spark generators available.  The picture below shows two examples of Piezo Electric spark generators.

 
         
Piezo spark generators come in the push button or rotary style.  The push button spark generator has one wire terminal on the bottom that connects to a wire running to the electrode.  Sometimes the push button spark generator has a second wire terminal below the push button that connects to a wire running to a side burner or a ground wire running to the electrode. The rotary spark generator can have up to 4 wiring terminals each with a wire running to an electrode.  

When you push the button or turn the knob on a Piezo spark generator you will hear a "snap".  As you bush the button or turn the knob, a spring is compressed and a hammer is pulled back and released.  The hammer strikes a quartz crystal and produces and electrical "charge" that runs down the wire to the electrode.  The spark is not particularly hot, and if there is any deterioration in the wiring, corrosion of the electrode or mounting bracket, the spark becomes weaker and often unreliable.

In my experience, the push button spark generators seem to last the longest.  The rotary spark generators fail when the black cap (bottom picture opposite side of the cylinder from the wire terminal) pops off due to fatigue and the parts inside the cylinder come out.  Your Piezo spark generator has failed when you no longer hear the "snap" when you push the button, or the knob on the rotary style spins loosely.

Replacement involves simply removing the old spark generator, installing a new one, and re-connecting the wiring.  This sometimes requires the removal of the front panel from the grill.  This is also a good time to check the wiring and electrodes to make sure there is not more than one problem with the ignition system.  When you install the new spark generator it is important to install one with the same number of wiring terminals.  If there are more terminals than wires, then a ground wire will have to be installed to ground the open terminal or the spark generator will not work properly.

Battery operated ignition systems were the next to appear on outdoor grills.  Battery operated system have the advantage of a repeated spark, a more reliable spark, and a hotter spark. Battery operated igniters use transformers to increase the voltage of the battery to produce a hotter spark.

Below are pictures of a AA and AAA spark generators..

  

The large, square portion of these spark generators is typically behind the control panel and the cap with the rubber boot is visible. The cap acts as the switch, pushing on the cap activates the spark generator. The cap is removed to replace the battery.  The AA spark generators can also have a cap without the rubber boot and a separate switch is used to activate the spark generators.

AA spark generators can have as many as 6 outlets, and some may have switch terminals as well as wiring terminals. AAA spark generators can have up to 4 wiring terminals and do not have switch terminals.  

Below are pictures of 9V spark generators.



9V spark generators are always completely concealed, usually behind the control panel, and are activated by a separate switch that is wired to the switch terminals. The battery is under the cap of the spark generator on the left and slides into the slot on the right hand side of the spark generator on the right.  Normally the battery can be changed by reaching under the control panel to access the battery compartment of the spark generator.  Some times the grease tray will need to be removed.  The 9V spark generator on the left comes in a 2 terminal and a 4 terminal model and multiple spark generators and switches are used on larger grills.  The 9V spark generator on the right can have as many as 6 terminals.

If the battery operated ignition system is working properly, the snapping of the sparks will be heard as long as the cap or switch is held down.  The most common failure is a dead battery, replacement of the battery is the first thing to try. If the battery has been allowed to corrode inside the spark generator, the spark generator will need to be replaced.  If a new battery does not fix the problem, then it may be failure of the spark generator itself, a wiring problem, an electrode problem, or a combination of problems.  Troubleshooting will have to be done to determine exactly what is working and what is not.  When replacing the spark generator, the replacement should have the same number of wire terminals as the original.  Unused, open terminals on the spark generator must be grounded for the spark generator to work properly.

As well as the spark generator, ignition systems have wires and electrodes. In some grills, only one burner is lit with the ignition system so there will only be the spark generator, a single wire, sometimes a ground wire, and a single electrode on one main burner. The remainder of the burners are lit using cross over tubes between the burners.  On more complicated ignition systems, each main burner and rear burner will have its on wire and electrode.  On some grill models, depending on the total number of burners, there may be multiple spark generators as well.

Below are examples of electrodes and wires.



All electrodes will have the electrode itself, a white insulator, and a mounting bracket.  Some electrodes have attached wires and some have separate wires.  The thicker and heavier the electrode material, the better the insulator, and the better the wire is heat insulated, the longer the electrode and wiring will last.

The electrode and wire on the left is typical of those found in inexpensive Chinese Import grills, note the thin electrode and thin insulation on the wire.  These type of electrodes and wires tend to fail fairly quickly.  These types of electrodes often use the burner itself for the ground point and the spark to ignite the gas will jump from the tip of the electrode to the burner.

The electrode on the right is from a higher quality grill.  The electrode is heavier and the insulation on the wire is much better.  This electrode also has a ground post, the spark jumps from the electrode to the ground post to ignite the gas.  This is a much more efficient system as the gap between the electrode and the ground post is easier to adjust, and maintain, than the gap between the electrode and the burner. This type of electrode and wire typically costs more to replace, but lasts for years.

The electrode has to ground to the fire box in order to work properly.  This is accomplished through the mounting bracket and is attached to the fire box with a bolt or screw.  The heavier the mounting bracket, the longer it will last and the better the ground will be.

Some electrodes mount to a hood/collector box that is attached to the fire box creating a ground point.  Below are pictures of some typical hoods/collector boxes.



The electrode will be attached to the hood/collector box at the mounting point with a bolt or screw.  The tip of the electrode will be inside the hood/collector box and the spark will jump from the tip of the electrode to the hood/collector box to ignite the gas and light the burner.

The hood/collector box provides some degree or protection for the electrode and helps to trap gas around the electrode making it easier for the spark to ignite the gas to light the burner.  As always, the thicker and heavier the hood/collector box is, the better ground it will provide and the longer it will last.

Typical failures of the wiring are cracks, breaks, or melting of the insulation caused by age or damage from overheating. This allows the spark to jump to ground before it reaches the tip of the electrode short circuiting the system.  The wire itself will also age and become less conductive over time.  Sometimes the insulation can be repaired, or the wiring will need to be replaced.  If the wire is part of the electrode assembly, then the electrode and wire are replaced. 

A crack or break in the insulator of the electrode will also allow the spark to jump to ground and short circuit the system. Replacement of the electrode fixes the problem.  The mounting bracket of the electrode can also corrode preventing the electrode to ground properly, or completely break off allowing the electrode to move away from the ground point preventing the spark from igniting the gas to light the burner.

If a wire or electrode needs to be replaced, it is always recommended to replace the wire, electrode, and hood/collector box at the same time.  If you are going to replace one electrode, wire, and hood, it is also a good idea to replace them all as failure of the remaining electrodes, wires, and hoods will not be far behind.

Flame Thrower ignition systems are the combination of a Piezo spark generator and the main burner valve itself.  Below is a picture of a Flame Thrower ignition.



These type of ignition systems are primarily found on less expensive Chinese import grills.  When the burner knob is pushed in, a jet of gas comes out of the flame thrower gas jet, and moves up the delivery tube. When the burner knob is turned, the hammer of the Piezo spark generator is pulled back and released creating an electrical current that travels through the wire to the tip of the electrode.  The spark jumps from the tip of the electrode igniting the gas coming out of the delivery tube and a jet of flame, hence the name flame thrower, shoots along the side of the burner igniting the gas in the burner and lighting the burner.  All of the Flamer Thrower ignition and valve sit behind the control panel and are not visible without removing the control panel.

Typical failures include the failure of the Piezo spark generator, damage to the insulation of the electrode wire, and damage to the white electrode insulator.  Since the Flame Thrower ignition is part of the valve itself, the only remedy to the typical problems is to replace the entire valve as component parts are not available. This is major work, and care must be taken to avoid a leak when replacing the valve.  This should be done by a qualified professional.

The most common problem, and what I believe to be a design flaw, which could result in a back flash fire behind the control panel creating more problems is the clogging of the Flame Thrower gas jet and/or the delivery tube. I find this most often in grills that are not used very often, and grills that set unused over an entire summer.  

The Flame Thrower gas jet has a very tiny orifice that can become plugged or partially plugged with dirt, etc.  This will either completely stop the flow of gas, or worse, partially stop the flow of gas causing the gas to flow out behind the control panel instead of into the delivery tube.  The delivery tube is the perfect home for spiders and insects to build nests. Insect or spiders nests inside the delivery tube will force the gas to flow out behind the control panel instead of the end of the delivery tube.  Repeated attempts to light the burner will result in an increasing amount of gas buildup behind the control panel.  If the spark from the electrode ignites the gas built up behind the control panel, a back flash fire will result that will melt parts of the valve and burn up the electrode wire resulting in the need to replace the entire valve. I see this on a regular basis with Flame Thrower type ignitions.

Hot Surface ignition systems are usually only found on high end outdoor grills.  Below is a picture of a hot surface igniter.


Hot surface igniters are similar to the "glow" plugs used to light gas ovens in the kitchen.  When the knob on the grill is pushed in, a micro switch sends an electrical current through the wiring and the element at the end of the igniter.  The element begins to heat up and glow.  When the element reaches the correct temperature, it ignites the gas coming from the burner and lights the burner.

Early hot surface ignition systems had very fine heating elements and worked on very low voltages such as 3.5 volts.  These systems were unreliable as any drop in voltage anywhere in the system would allow the element to glow, but not get hot enough to ignite the gas from the burner.  Newer systems us the heavy igniters pictured above and 12 V to provide a reliable system.

Typical failures are the micro switch on the valve, damage to the wiring, or failure of the element. Since these systems involve lots of wiring behind the front control panel, repairs should be left to professionals.

 
 

Gas Grill Components - Burners and Grates

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Outdoor Grills 101

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Now that grilling season is upon us, it is time to take a look at different types of grills, grill quality, and how grills work so you will get the most enjoyment out of your new grill, or your existing grill.


Charcoal or Gas

The age old question: "Charcoal or Gas".  This will be debated forever and there is no right or wrong answer.  I will give just a few thoughts.

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