You've identified a common problem with older buildings and additions. Let's break down your questions and the relevant code sections

Understanding 225.30 and Exceptions
225.30 (Number of Supplies) This section is the core of your problem. It generally limits the number of supplies (feeders or branch circuits) to one between a building and another. The purpose is to ensure a single point of disconnect for safety and coordination. Exception 3 (Common Supply Equipment) This exception, which you noted, allows for more than one supply if all of the following conditions are met: Only Qualified People Service or Maintain

This is a significant qualifier. The building's electrical system and those authorized to work on it must be under continuous supervision by qualified persons. This is often a deal-breaker for typical installations as it implies a dedicated maintenance staff.



Documented Switching Procedures

You must have documented, safe switching procedures to de-energize the building's electrical system. This goes beyond simply knowing where the breakers are; it requires a documented process.

Equipment is Identified

You must clearly label all the supply equipment and feeders.

Exception 6 (More Than One Building or Structure)

This exception allows for up to six feeders or branch circuits when supplying more than one building or structure under single management.

Addressing Your Specific Situation1.

The "Easy Fix" (Branch Circuit from Building B)

Absolutely, moving the branch circuit from Building B to Building A simplifies compliance. You would want to ensure that the circuit is appropriately sized and protected for the load it serves.2.

Evaluating 225.30(B) "Common Supply Equipment"

Your assessment is potentially correct. If you could convert everything to feeders from a single panel in Building A and meet all the conditions of Exception 3 (qualified personnel, documented procedures, identification), you could have more than one feeder.

Feeder Conversion

Think about what it would take to convert existing branch circuits to feeders. This often involves replacing the overcurrent protection at the source (Building A), possibly upgrading conductors to accommodate the feeder size, and ensuring appropriate overcurrent protection at Building C for each unit's load.

Panel in Building A

Is the panel in Building A capable of handling the total load of all the units in Building C? Consider future expansion and demand factors.3.

Other Limits to Number of Feeders Between Buildings



225.30 itself IS the primary limit! There is no other section that increases the number of allowable supplies between buildings or structures.

Exception 6 (More Than One Building)

Since you're dealing with one building (Building C) with multiple units, this exception doesn't seem to apply.

Recommended Steps for Compliance1.

Load Calculation

Perform a thorough load calculation for each unit in Building C and the building as a whole. Account for existing loads, potential future loads, and any applicable demand factors. This is crucial for determining the necessary feeder sizes and panel capacity.2.

Evaluate Exception 3

Honestly assess whether you can truly meet all the requirements for Exception 3 (Common Supply Equipment). If not, this option is likely off the table.3.

Consolidation/Subpanel

The cleanest solution is often to consolidate all the feeders from Building A into a single point in Building C (a subpanel). This would require running a single feeder (or a few, if necessary for capacity) from Building A to a new main disconnect/panelboard in Building C. Then, you would redistribute the power within Building C to the individual units.4.

Permitting and Inspection

Engage with your local electrical inspector early in the process. They can provide guidance on local interpretations of the code and ensure your plan meets their requirements.

Important Considerations

Safety

Prioritize safety in all your electrical work. Work with qualified electricians and ensure all installations meet code.

Future Expansion

Design your electrical system with future expansion in mind. Provide sufficient capacity for anticipated growth.

Documentation:* Maintain accurate records of all electrical work, including load calculations, circuit diagrams, and equipment specifications.In summary, cleaning up this electrical mess will likely involve consolidating the electrical supply at Building C, potentially through a subpanel fed by a single feeder from Building A. Carefully evaluate whether you can truly meet the requirements of Exception 3, but it's often impractical. Engage with your local electrical inspector for guidance and approval throughout the process. Flag for review