Okay, let's break down the requirements for disconnects around transformers in your situation. This is a common scenario for long distance services.

Understanding the Code (NEC)

The NEC (National Electrical Code) primarily focuses on safety. The relevant articles are: Article 240: Overcurrent Protection (particularly 240.21 for transformer secondary protection) Article 450: Transformers Article 225: Outside Branch Circuits and Feeders Article 230: ServicesKey Considerations1. Overcurrent Protection is Paramount

The primary goal is to protect the transformers and conductors from overcurrents (faults or overloads).2.

Transformer Primary and Secondary Protection

You must protect both the primary and secondary sides of the transformers. How you do this depends on several factors, but you need to be compliant with NEC 450.3.
3.

Disconnect Requirements

The NEC generally requires a disconnect at or near the transformer (450.14).
4.

Overcurrent Protection Location

The placement of overcurrent protection (fuses or breakers) depends on whether you are applying the primary-only protection rule or the primary and secondary protection rule.

Analyzing Your Specific Setup Meter/Main/Transformer (at Pole)

You have a 200A meter/main disconnect feeding a transformer to step-up to 480V. The 200A breaker in your meter main acts as the overcurrent protection for the primary of your step-up transformer.

1000ft 480V Run

This long run is why you're stepping up the voltage.

Transformer (at House) and Disconnect in Question

You have a step-down transformer to bring the 480V back down to your utilization voltage (presumably 120/240V single-phase). This is where your question arises.

Answering Your Question: Fused vs. Non-Fused Disconnect

The question of whether the disconnect must be fused depends on how you're providing overcurrent protection for the secondary side of the step-down transformer near the house. Here are the possibilities

Scenario 1: Primary-Only Protection (NEC 450.3(B))

Explanation

In this scenario, you are relying solely on the overcurrent protection on the primary side (i.e., the 200A breaker in your meter/main at the pole) to protect the secondary side as well. This is allowed under very specific conditions outlined in NEC 450.3(B). The most common condition is that the primary overcurrent device must be sized to protect the secondary conductors. This is highly dependent on the transformer impedance and the conductor ampacity.

Implication for Disconnect

If you're relying solely on the primary-side overcurrent protection (200A breaker at the pole), then the disconnect at the step-down transformer does not need to be fused. It simply needs to be a suitable disconnect switch rated for the voltage and current.

Caveats

This is rarely done because you need to match the transformer, wire, and breaker size to get this to work. The primary overcurrent protection must not exceed the values shown in Table 450.3(B). If the primary overcurrent protection exceeds the values in Table 450.3(B) then you have to apply the secondary protection rules of 450.3(A) The primary conductor from the pole to the transformer by the house must be sized to carry the load and also be protected by the primary breaker per NEC 240.21(C).

Scenario 2: Primary and Secondary Protection (NEC 450.3(A)) Explanation

This is the more common and often safer approach. You provide overcurrent protection on both the primary and secondary sides of the transformer. This is almost always the preferred method.

Implication for Disconnect

If you're providing overcurrent protection on the secondary side of the transformer at the house, then the disconnect does not need to be fused, but you must have a separate overcurrent protection device (fuses or a circuit breaker) immediately after the transformer secondary. The disco can be ahead of or after the overcurrent device, provided it can be opened with the overcurrent device in the on position.

Fuse Sizing on the Secondary

The secondary overcurrent protection must be sized according to NEC 450.3(A) generally at 125% of the transformer's secondary current rating.

Practical Considerations Ease of Maintenance/Troubleshooting

Having a fused disconnect at the house-end transformer can make troubleshooting easier. You can isolate the transformer and downstream circuits for testing and repairs.

Code Compliance

Double-check your calculations and consult with a qualified electrician or electrical engineer in your jurisdiction to ensure full compliance with the NEC and any local codes. Your local inspector is the final authority.

Availability

You're finding it difficult to find a 480V, 200A, 2-pole fused disconnect. That's because it's not a standard configuration. A more common configuration is a 3-pole disconnect, and you would only use two of the poles. Alternatively, you could use a 480V 3-pole disconnect and only utilize two of the poles for your 2-phase system.

Recommendations1. Consult with a Qualified Professional

I strongly recommend consulting with a licensed electrician or electrical engineer who is familiar with the NEC and local codes in your area. They can perform the necessary calculations, select the appropriate equipment, and ensure a safe and code-compliant installation.2.

Consider Primary and Secondary Protection (Scenario 2)

While it might involve a bit more upfront cost, the Primary and Secondary Protection approach (NEC 450.3(A)) is generally the safer and more reliable option. It provides better protection for both the transformer and the downstream circuits.
3.

Document Everything

Keep detailed records of all calculations, equipment specifications, and installation procedures. This will be helpful for future maintenance and troubleshooting.

In Summary

The step-down transformer disco may not need to be fused if the transformer is protected by the 200A breaker at the sub pole. This is under very specific conditions outlined in NEC 450.3(B) that may require significant recalculations and adjustments to the equipment. Alternatively, you can install a non-fused disco and a separate overcurrent protection. Either way, it is highly recommended to consult with a professional to make sure it is safe and within code.Disclaimer: This information is for general guidance only and does not constitute professional electrical engineering advice. Always consult with a qualified and licensed electrician or engineer for specific advice related to your project. Flag for review