No, a 240/120V bolt-on, center feed breaker (common in older ITE panels) will NOT fit and is NOT rated for use in a 480V ITE panelboard.

Here's why: Voltage Rating

The 240/120V breaker is designed and tested for a maximum voltage of 240V. Using it in a 480V system would far exceed its design limits. This presents a very high risk of catastrophic failure, arc flash, and fire.

Physical Fit

While it might seem like it could physically fit (depending on the specific model and panel), the internal bus bar spacing, insulation, and clearances in a 480V panel are different than a 240V panel. Forcing a mismatched breaker can damage the panelboard.

Arcing and Insulation Breakdown

The higher voltage would likely lead to arcing within the breaker, destroying it and potentially damaging the panel. The breaker's insulation is not designed to withstand 480V.

Listing and Labeling

Breakers are listed and labeled by testing laboratories (like UL) for specific voltage and application ratings. Using a breaker outside its listed ratings voids the listing and violates electrical codes.

Important Safety Note

Using the wrong type of breaker is extremely dangerous and could lead to serious injury, death, or property damage.

Always use breakers that are specifically rated and approved for the voltage and application of the panelboard. If you are unsure, consult a qualified electrician. Flag for review