480-24Vac CPT Primary Protection


Is it acceptable to have secondary only protection for a 480V-24Vac (2-Wire) 300VA transformer? The transformer has a built-in circuit breaker wired to the secondary (24V) side of the transformer. It feeds control circuits. I believe that 450.3 applies, but I'm not sure if there is something out there that would give an exception to this rule. I thought possibly Article 725, but can't find anything on the topic.

The transformer is fed from the primary of a fused disconnect switch (Tap-Rule).

All help is appreciated.


Senior Member
The smallest reading that would be required for a circuit breaker on the primary as overcurrent protection would be a 15 amp breaker. As long as the branch circuit breaker was a 15 amp breaker you would be fine.