The Ignition Transformer



The Ignition transformer takes line voltage and steps it up to the approximately 10,000 volts to create the spark that jumps the gap between the ignition electrodes. The voltage and amperage supplied to the cleaning system are not appropriate for creating the needed ignition spark.


The pump motor requires 115, 230 or 460 volts for operation. The ignition electrodes for the oil burner, however, will require a much higher voltage (usually 8,000 to 10,000 volts) for the ignition spark to arc across the gap between the electrodes.

What The Ignition Transformer Does
A transformer is used to increase the voltage from the voltage supplied by the electric utility to the voltage required by the ignition electrodes. The power supplied to a transformer always equals the power provided by the transformer. This basic expression of a transformer always equals the power provided by the transformer. This basic expression of a fundamental physical principle is expressed as "power in = power out."

A transformer increases or decreases amperage exactly inversely to any increase or decrease in voltage. In other words, if a transformer doubles the voltage of a 20 amp, 115-volt current, and the result would be a 230-volt, 10 amp current. Transformers come in two basic types: step-up, which increase voltage and step-down, which reduce voltage. A step-up transformer is used in the ignition transformer role.

The Flip-Up Top
In most modern gun-type burners the ignition transformer is mounted on a hinge on the burner assembly. When ignition transformer swings shut like a door, the bus bars on the transformer make contact with the electrodes. When power is provided to the transformer, a spark is created at the gap between the electrodes. The transformer can be swung back for testing or inspection of the bus bars to see if they are properly aligned. Look for signs of arcing within the burner housing. If the transformer is bad, it should be replaced. Replace with a transformer of the same rated output.

Caution: Do not use a large insulated screwdriver to check for arcing between the bus bars. Use proper transformer testing equipment or turn the job over to a qualified electrician.

Note: 12-volt ignition systems and new, solid-state ignition systems have slightly different components but operate on the same principles. Full-featured systems with multiple-pass coils will generally have the ignition transformer mounted with other electrical components. Check the equipment manual to identify the proper transformer.

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