Can you use parallel conductors from parallel circuit breakers?

Yes, you can use parallel conductors from parallel circuit breakers to feed the primary side of a step-up transformer. However, there are some requirements and considerations

Requirements:
The conductors must be sized to handle the full current draw of the transformer. The circuit breakers must be rated for the maximum current that the conductors can handle. The circuit breakers must be interlocked to prevent one breaker from tripping independently of the other. The conductors must be connected in parallel at both the transformer and the circuit breaker.

Considerations

The voltage drop in the conductors must be within acceptable limits. The conductors must be properly protected from physical damage. The conductors must be installed in accordance with applicable electrical codes.

Can 500 MCM fit on a 200A CB?

It depends on the specific circuit breaker being used. Some 200A circuit breakers can accommodate 500 MCM conductors, while others may require a larger breaker. Refer to the manufacturer's specifications for the specific circuit breaker you are using.

Is there a way to interlock the 2 breakers to use smaller conductors (3/0)?

Yes, there are ways to interlock two circuit breakers to allow the use of smaller conductors. One common method is to use a mechanical interlock, such as a breaker interlock kit. This kit connects the two circuit breakers together mechanically, ensuring that they trip simultaneously.

Other Solutions

If using parallel conductors is not feasible, there are other solutions to consider: Use a larger distribution panel

Install a distribution panel that can accommodate 400A circuit breakers.

Use a different transformer

Select a transformer that has a primary voltage rating of 225V. This will allow you to use a single 225A circuit breaker to feed the transformer.

Use a fused disconnect switch

Install a fused disconnect switch with a 400A fuse between the distribution panel and the transformer. This will provide overcurrent protection and allow you to use 500 MCM conductors.

Recommendation

Based on the information provided, it is recommended to use parallel conductors and circuit breakers with the following specifications: Conductors

500 MCM

Circuit Breakers

2 x 200A, 3P with a mechanical interlock kit*

Distribution Panel: 400A capableThis solution will provide the necessary overcurrent protection and ensure that the conductors are properly sized to handle the full current draw of the transformer. Flag for review