Here comes Columbus Day, the final test of how well we've prepared our customer's systems for the winter's snowy blasts. If the phone rings off the wall, we've slipped. If all is quiet, we've passed the test.
That's how I learned my lesson on high voltage ignition.
I'll admit, this customer was very patient, but even patience can be exhausted. We'd been back to his home three days in a row, each to deal with the same complaint. The burner locked out around 11 p.m. and he had to reset it. Once the reset button was touched, the burner fired off, never skipping a beat. Sound familiar? Something changed, but what?
Now we started trying to find that elusive gremlin that was hiding deep within the burner. It was the burner, so we at least limited our search. Now the questions:
“Your burner and controls are working fine. Let's try and narrow things down. Do the lights dim or anything like that just before the burner locks out?” I asked.
“I'm watching TV, the lights are off. What are you trying to find out?”
“Do you notice anything unusual electrically?”
“If you're wondering about the voltage, I've got a volt meter and can watch it if that helps.”
Lucky me, I was working for a ham radio operator who just happened to have a panel voltmeter. He watched that night and as I suspected, the voltage dropped to about 100 volts each evening, right around the time a factory down the road changed shifts. I suppose it happened at other times during the day, but this was happening when he turned up the heat, just before heading off to bed. Voltage drops and iron-core transformers, the perfect combinations for a difficult service call.
Oil burners use high-pressure atomization for combustion. Oil takes the proper mix of a “triangle of combustion” to ignite - heat, air and fuel. Without sufficient heat, you'll never get the oil to light, at least as it should.
The heat for ignition is created at the tips of the electrodes, with a voltage that must exceed 9,000 volts AC for an American-type burner. Nine thousand volts really is a minimum to produce an arc that would light the burner, though if the draft is high or the electrode gap is set wrong, you still may not have ignition. Fortunately, a typical iron-core transformer is rated with higher output voltage, minimally 10,000 volts when there is an input of 120 volts AC. That's when everything is working as designed, but my poor customer was a step away from center.
Input & Output
The issue with iron-core transformers is that voltage output is directly proportional to voltage input. An ignition transformer is nothing more than two windings around an iron core. The winding connected to a “line” is called the primary, with an induced voltage coming from the secondary winding. The secondary winding is where the electrodes are connected, with an arc produced across the space between the electrodes. When a transformer is wound with more secondary windings it is called a step-up transformer, the design of an ignition transformer.
My customer recorded an input voltage of 95 volts when the burner locked out. His transformer was typical, rated for 10,000-volt output at 120 VAC input. That was about a 20 percent drop in input voltage. Remember that secondary output is directly proportional to input. A 20-percent drop of input means an output of 8,000 volts, far from “hot” enough to light the oil. All we needed to do was convince the electric company to “turn up the juice,, or …
Luckily we had a commercial transformer that fit this burner. The design of the commercial transformer was an output rating of 12,000-volts at 120 VAC input. With a 20-percent voltage reduction there still was an output of about 9,600 volts, well above the 9,000-volt minimum needed for ignition. This one finally worked.
Education can be expensive, especially when the solution is not at hand. These calls were just before solid-state igniters were readily available. I've got to admit, there was a lot of “what ifs” asked over coffee at the supply house, with answers ranging from “get an electrician” to the final suggestion of a 12,000 volt transformer. That was my fix, though I'd use an igniter today.
Eventually, one supplier developed igniters for their burners, with plates that adapted the igniters to other brands of burners. The advantage was a high-voltage output across a wide range of input voltages. The biggest disadvantage then was distribution; few wholesalers bought into the selling features right off the bat, making finding solid-state igniters hard to find.
That was then. Today there is an easier solution. Now the igniter is the standard for most residential burners. Now there are more manufacturers, so each of us can choose one that meets our criteria. Replacing a transformer with a transformer no longer makes sense, unless you are dealing with an obsolete burner or “ram's horn” electrodes. How can I make such a broad statement? Because through a wide range of applications, an igniter works.
In a nutshell, the igniter is a solid-state control that modifies the phase of the electrical output, creating average output voltages exceeding 14,000 volts. Output is sufficient for ignition across a wide range of input voltages. Heat is not a byproduct of the operation, very much like comparing an LED or fluorescent lamp to an incandescent light.
There are electrical components, not numerous windings of wire inducing current flow. You still need a complete circuit, including a proper common and ground. Without them, you will encounter a new form of service call - a “weak” igniter. In theory, the igniter should be a “go/no go” device, but in practical application there will be “weak outputs” or phantom failures during cycles.
One common ground issue is when the plate is corroded around the mounting screws. Remove, clean the screw holes and replace the screws. Sometimes the repair is that simple. Often just replacing the igniter masks this problem - new screws tightened into a rust-free plate.
Testing an igniter is similar to testing a transformer. Do not, however, use a transformer tester to test an igniter! A transformer tester is not designed for this application, and the higher voltage will damage it. If you are going to test an igniter, follow the manufacturer's service bulletins or use an igniter tester. I'm hesitant to discuss pulling an arc across the contacts because this can be a safety issue. You are dealing with high voltage though low amps, and could either destroy the igniter if you short it out, or injure yourself. Please, use a properly designed tester!
Why switch to igniters over transformers? Let's go over all the advantages.
The first advantage is weight on your van. An iron-core transformer weighs about 8 lbs., compared to 1 lb. for an igniter. That means if you are stocking a service van and want two transformers for each of the three major American burner manufacturers, you've just added 48 lbs. to the van. Switch to igniters and the added weight plummets to 6 lbs., a 42-lb. savings in a time when saving weight means saving vehicle costs.
However, sometimes the lack of mass causes customer complaints about noise. Weight means mass and mass reduces noise, similar to putting furniture in an empty house. When that complaint comes - and it will - try switching from intermittent ignition to interrupted. That will lessen the noise by discontinuing the spark after ignition is established.
The next advantage is energy costs. An igniter is a solid-state device, designed with the arc as part of the circuit. Iron-core transformers produce heat as a byproduct, wasted through the windings. Energy doesn't discriminate; you pay for what runs through even if you can't use it. It's not uncommon to realize a component energy savings of 40 percent simply by changing from a transformer to an igniter.
My favorite advantage of the igniter is a very consistent and reliable output voltage over varied input voltages. One of my training aids was a variable power source connected to an oil burner with a clear air tube.
If you'd like a real visual “proof of the pudding” test, try this: Get a burner equipped with a clear tube, a splitphase induction burner motor and a transformer. Wire the burner into a variable AC power control and start the burner at 110 volts AC. Turn the voltage up to 130 volts and watch the color of the arc. Now turn the voltage down slowly until you reach 90 volts. I won't spoil the fun, but after this, swap the transformer for an igniter, then swap out the motor with a PSC motor. That arc, which faded into the air stream at low voltage, will suddenly stay viable at lowered input voltages.
Do you have customers with cold oil? The higher voltage of an igniter aids in the ignition of cold oil. We can't outfox physics. The first law of thermodynamics says hot goes to cold; the greater the difference, the faster the movement. An arc has to heat atomized oil to its “flame point,” about 640 degrees F. When the oil is extremely cold, the arc needs more potential to provide reliable ignition. With an igniter, the peak voltage can be double that of a transformer, cycling many more times per second than a transformer. These additional cycles, coupled with the higher peak voltage, contribute to ignition even on outdoor installations.
Now the pitfalls of an igniter. You need to set the electrodes properly. If the electrodes are too far forward, the spark may arc out to the combustion head. If the electrodes are too close, the arc will not carry into the oil pattern. Igniters have an intense spark. Transformers will arc and flow to the tip of the electrodes, commonly referred to as the “Jacobs Ladder” effect. Igniters take the path of least resistance. If the electrodes are close to each other, at some point that's where the arc will occur, a problem with “ram's horn” electrodes that are found on larger commercial burners. That is an application for a transformer.
The intense spark will reduce electrode wear. When an arc occurs, it will hold that position during the cycle, rather than fluctuating back and forth like an arc from an arc welder. Ever look at the end of the rod after arc welding? The tip is distorted, often concave. Electrodes on transformer applications wear the same way, hollowing out as the arc is established from electrical cycle to electrical cycle. Electrodes last longer with igniters, another savings from such a simple change.
We've got some great products in the oil industry, each making oil heat more reliable. Next time you're in a supply house, give the igniter a try. You won't regret that simple business decision.