Okay, let's break down the requirements for service equipment in Baltimore, considering NEC and local amendments. Your scenario is a common one, and the code requirements can be tricky.

Understanding the Core Issue

The key question is whether your configuration complies with the NEC rules for service disconnecting means and overcurrent protection. The NEC generally wants a clear, easily accessible, and coordinated way to disconnect the entire service from the utility.

Analyzing Your Current Configuration Service End Box and CT Cabinet

This is standard for larger services where metering requires current transformers (CTs).

Four 400A Service Switches Tapped from the CT Cabinet

This is where the question of compliance arises.

NEC and Potential Baltimore Amendments Considerations1. Number of Service Disconnecting Means (NEC 230.71)

The NEC generally allows up to six service disconnecting means to serve as the main disconnect for a building.

Your current design meets this requirement. You have four service switches.2. Grouping of Service Disconnecting Means (NEC 230.72(A))

The service disconnecting means MUST be grouped and in a readily accessible location. They should also be marked to indicate they are service disconnects.

If your four switches are grouped together, this would be fine.3. Overcurrent Protection (NEC 230.90)

Each service conductor must have overcurrent protection at or ahead of its point of connection to the service disconnecting means.

This is a critical point. Typically, the fuses or circuit breakers in your 400A service switches would provide this overcurrent protection. However, the NEC 230.90 Exception No. 3 allows for the sum of the overcurrent protection on the 400A switches to exceed the ampacity of the service entrance conductors (coming to the CT cabinet).4. Accessibility (NEC 230.205)

Service equipment MUST be readily accessible, both to the utility and the building owner/operator.5.

Baltimore Amendments



THIS IS CRUCIAL. Baltimore may have amendments to the NEC that further restrict service configurations. For example, some jurisdictions require a single main service disconnect regardless of load size. You absolutely need to check the Baltimore City Electrical Code for any local amendments to the NEC. Call the Baltimore City Department of Housing and Community Development, Electrical Inspections Division, to confirm the requirements.Two Potential Solutions and Recommendation

Given the above and the need to confirm Baltimore-specific requirements, here are two potential solutions: Option 1: Your Current Design (Four 400A Service Switches) Pros

Simpler, potentially less expensive. Meets the NEC's allowance for up to six service disconnects.

Cons

Requires VERY careful coordination and compliance with the grouping, accessibility, and marking requirements of the NEC. May not be permitted by Baltimore amendments.

Conditions to meet for Option 1



Confirm Baltimore allows multiple service disconnects. The four 400A switches are grouped together. Each switch is clearly labeled as a "Service Disconnect." The switches are readily accessible. Option 2: Single Main Fused Disconnect + Downstream Switchboard Pros

Cleaner, more traditional approach. Often easier for inspectors to understand and approve. May be required by Baltimore amendments. Generally provides more flexibility downstream.

Cons

More expensive (requires an additional piece of equipment).

How it works

1. Incoming service conductors enter the Service End Box, then CT cabinet.
2. From the CT cabinet, conductors go to a single, fused service disconnect (e.g., a 1200A or 1600A switch, sized appropriately for the total load). The fuse size is selected to protect the service entrance conductors.3. Downstream from this main fused disconnect is a switchboard with your four 400A switches (or whatever distribution you need). These downstream switches are not considered service disconnects.

Recommendation1. Call Baltimore City Electrical Inspections Division IMMEDIATELY. Describe your planned configuration (four 400A switches directly off the CT cabinet) and ask if it's acceptable under Baltimore's local amendments to the NEC. This is the MOST important step.2. If Baltimore says "no" to the four-switch configuration, you'll have to go with Option 2 (the single fused disconnect and downstream switchboard).3. If Baltimore says "yes" to the four-switch configuration, proceed cautiously. Make sure you meticulously comply with the grouping, accessibility, and marking requirements of the NEC.4. In either case, provide clear and detailed documentation in your submittal drawings. Show the service entrance conductors, CT cabinet, disconnect switch locations, fuse/breaker sizes, and appropriate labels.

Example Phone Call Script

"Hello, I'm an electrical engineer working on a project in Baltimore. I'm designing the service entrance and want to confirm the requirements for service disconnecting means. I'm planning to have a CT cabinet, and then tap four 400A service switches directly off the secondary of the CT cabinet. Does the City of Baltimore allow multiple service disconnects like this, or is a single main service disconnect required?"

Important Notes



Coordinate with the Utility

The utility company (BGE, most likely) will also have requirements for service entrances and metering. Make sure your design meets their specifications as well.

Professional Engineer Stamp

You must have a licensed Professional Engineer stamp and seal your electrical drawings for submission to the City of Baltimore.*

Good Communication with the Inspector: A good working relationship with the electrical inspector can be invaluable. Be open to their suggestions and address any concerns they may have.By following these steps, you'll be well on your way to designing a compliant and safe service entrance for your Baltimore project. Good luck! Flag for review