Siemens Ignition transformer AGG5.220

The Siemens AGG5.220 is an ignition transformer, a component found in the ignition train of burners. It steps up the mains voltage to a level sufficient to create a spark across the ignition electrode gap. The transformer is energised only during the ignition phase, under command from the burner control. Once the flame is established, power to the transformer is cut, as it is not used during continuous operation.

For an ignition transformer of this class, the primary voltage must match the burner's supply—230 V is the most common, but 110 V and 24 V variants exist. The secondary voltage and current determine spark energy and must be compatible with the electrode gap and the burner control's ignition circuit. Duty cycle is also relevant: standard ignition transformers are rated for intermittent operation, typically under 10% duty. Mechanical dimensions, mounting pattern, and terminal type (e.g., cable entry or plug connector) must fit the burner housing and the existing cable.

A cracked or hardened ignition cable can leak current to earth, mimicking a faulty transformer and preventing ignition. Always inspect the cable before condemning the transformer.