Okay, let's break down the considerations for your 480V, 4500A service and the options for connecting the pad-mounted transformer to the indoor switchgear, focusing on cost-effectiveness.

First Question: Cablebus/Busduct Compatibility with Pad-Mounted Transformers Typically No Direct Connection

You're right that cablebus and busduct are most commonly associated with substation-style transformers that have a throat or flange specifically designed for bolting directly to the busduct. Pad-mounted transformers generally do not have this feature.

Conversion/Adaptation is Possible (But Complex)

It is possible to create an adapter section that transitions from the pad-mounted transformer's terminals to a busduct or cablebus system. However, this is a custom engineering solution. It would involve:

A Custom Transition Box

A metal enclosure built to connect to the transformer's secondary terminals. This enclosure would need to be properly sized for the ampacity and fault current.

Bus Bars Inside the Transition Box

Heavy-duty bus bars inside the box to distribute the current from the transformer terminals to the busduct/cablebus interface.

Insulators and Support

Robust insulators and mechanical supports to secure the bus bars within the transition box.

Proper Bonding and Grounding

Critical for safety and code compliance.

Second Question: Cost Advantage of Overhead Cablebus/Busduct vs. Underground Conduits Underground Conduits (Typical Scenario)

The typical approach for this short distance would be multiple parallel runs of large conductors in underground conduits.

Cablebus/Busduct Potential Advantages (With Caveats)



Labor Cost (Potentially Lower)

Cablebus/busduct could have lower labor costs, especially if the conduit installation is difficult or congested. However, this depends heavily on the specific site conditions, the complexity of adapting to the transformer, and the ease of routing the overhead run.

Space Savings (Maybe)

If you have very limited space below grade or near the building, an overhead run might be more compact, avoiding conflicts with existing utilities. However, you'll need to account for clearances above the busduct/cablebus.

Ampacity and Cooling

Busduct/cablebus has excellent heat dissipation due to open-air construction, this is likely not a factor at only 10 feet.

Cablebus/Busduct Potential Disadvantages



Custom Engineering Costs

The biggest disadvantage is the significant cost of the custom transition box and engineering required to adapt the busduct/cablebus to the pad-mounted transformer. This cost can easily outweigh any savings in labor for running the conductors.

Material Cost (Higher)

Busduct and cablebus are generally more expensive per amp than appropriately sized conductors in conduit.

Aesthetics

An overhead busduct/cablebus run might not be aesthetically pleasing, especially if it's highly visible.

Coordination

Adding an overhead run requires careful coordination with other building elements and potential obstructions.

Future Modifications

Making changes to busduct/cablebus after installation can be more complex and expensive than re-pulling conductors in conduit.

Third Question: Cablebus vs. Busduct for a 10-Foot Run For such a short distance, the cost difference between cablebus and busduct might not be significant. Both are likely to be more expensive than conduit and cable. Rigid busduct is usually less expensive than cable bus.Conclusion and RecommendationFor a 10-foot run from a standard pad-mounted transformer to indoor switchgear, stick with underground conduits and parallel conductor runs.Here's why: Cost

It's almost certain to be the most cost-effective approach.

Simplicity

It's the simplest, most straightforward installation method.

Reliability

Properly installed conduits and conductors are very reliable.

Maintainability

Replacing or upgrading conductors in conduit is relatively easy in the future.

No Custom Engineering

You avoid the significant expense and complexity of a custom transition box for busduct/cablebus.

Here's a simplified thought process


Underground Conduits

This is the default for padmount to switchgear. Get a quote for this first.2.

Custom Busduct/Cablebus

Get a quote for the complete solution, including the custom transition, engineering, and installation.3.

Compare

The underground conduit solution will almost certainly be the winner.

Important Considerations Short Circuit Current Rating

Regardless of which method you choose, make absolutely sure that all components (conductors, bus bars, switchgear, etc.) are properly rated for the available short-circuit current at the transformer secondary. This is a critical safety consideration.

NEC Compliance: Ensure that the entire installation complies with the National Electrical Code (NEC) and any local electrical codes.In summary, while cablebus and busduct have their place, they're not generally a good fit for this particular scenario due to the transformer type and the short distance involved.I highly recommend getting multiple quotes and discussing the options with qualified electrical contractors and engineers who have experience with both conduit installations and busduct/cablebus systems. This will give you the most accurate cost comparison and ensure a safe and reliable installation. Flag for review