A series-rated system allows a downstream circuit breaker with a lower interrupting rating (AIC) to be used where the available fault current is higher, provided it is protected by a specific upstream breaker or fuse combination that has been tested and listed to work together.

Simple Example

If the available fault current is 42 kA, a 10 kAIC downstream breaker may be used with a 65 kAIC upstream breaker only when that specific combination is manufacturer-tested and listed for a series rating of at least 42 kA.

65 kAIC Upstream Breaker → 10 kAIC Downstream Breaker

A higher-rated upstream breaker does not automatically make the downstream breaker series rated. The specific combination must be approved for series operation.

What Should Be Shown on the Electrical Drawings?

When a series-rated system is used, the electrical drawings should clearly indicate:

• Available fault current at the applicable equipment.
• Required series rating in kA.
• Upstream and downstream protective devices that form the listed combination.
• Series-rating requirements on the single-line diagram and/or panel schedules.
• A requirement that the contractor verify the exact breaker/fuse combination using the manufacturer’s published series-rating tables.
• Required permanent series-rating field labeling.

Series-rated systems must be properly selected, coordinated, installed, and labeled in accordance with NEC 240.86 and 110.22(C).

Important: Replacing or substituting a breaker can invalidate the series rating. Always verify replacement devices against the manufacturer’s listed series-rated combinations.

Example Using the Square D Series-Rating Chart

The Square D chart shown above provides a good example.

Assume the calculated available fault current at a 240V system is:

Available Fault Current = 50 kA

From the Square D chart, we can identify a tested combination with a:

Series Combination Rating = 65 kA at 240V

For the highlighted combination, the chart identifies:

Upstream Square D Breaker:
LH, MG, MJ, MH, PG, PA (1600), or RG (2000), as applicable to the manufacturer’s table

Downstream Square D Breaker:
QD, maximum 225A

Listed Series Rating:
65 kA at 240V

Therefore:

Upstream Listed Breaker
↓
QD Breaker — Up to 225A
↓
Series Combination Rating = 65 kA

If the available fault current is 50 kA:

50 kA Available Fault Current < 65 kA Series Rating

Therefore, this combination can be acceptable from a series-rating standpoint, provided the exact equipment configuration and all manufacturer and NEC requirements are satisfied.

As residential and commercial electrical demand continues to increase with electric vehicles (EVs), heat pumps, electric water heaters, battery storage, and electrification, traditional service upgrades are becoming increasingly expensive and difficult. The National Electrical Code (NEC) 2023 recognizes this challenge by providing a framework for Energy Management Systems (EMS) that intelligently manage electrical loads while maintaining safe operation.

For homeowners, contractors, engineers, and manufacturers, Article 750 represents one of the most significant changes in modern electrical design.

What Is an Energy Management System (EMS)?

An Energy Management System (EMS) continuously monitors electrical demand and automatically controls selected loads to ensure that the service or feeder rating is not exceeded.

A modern EMS can monitor real-time demand, prioritize loads, temporarily reduce or delay nonessential loads, automatically restore loads when capacity becomes available, and optimize energy usage while maintaining electrical safety.

NEC 2023 Article 750

Article 750 is the primary NEC article governing Energy Management Systems.

Key sections include:
• 750.1 – Scope
• 750.30(A) – Listed or identified equipment
• 750.30(B) – Installation requirements
• 750.30(C) – Load management
• 750.30(C)(1) – Managed loads and feeder/service sizing
• 750.30(C)(2) – Control requirements
• 750.30(C)(3) – Fail-safe operation

Load Calculations Under NEC 2023

One of the most impactful features of Article 750 is its recognition of managed loads. When an EMS complies with Article 750 and automatically controls electrical demand, certain managed loads may not need to be included when sizing service conductors and feeders, provided all applicable NEC requirements are satisfied.

Examples include EV chargers, electric water heaters, HVAC equipment, heat pumps, pool and spa heaters, and other controllable high-demand loads.

Electric Vehicle Charging

Article 625 governs Electric Vehicle Power Transfer Systems. Section 625.42(A) permits Automatic Load Management Systems (ALMS) that automatically adjust EV charging current based on available electrical capacity. When combined with an EMS complying with Article 750, EV charging can be intelligently managed.

Why EMS Matters

Without an EMS, adding new electric loads often requires larger electrical services, new conductors, utility upgrades, and higher installation costs. An EMS can often eliminate or postpone these upgrades by intelligently controlling demand.

Typical Managed Loads

Typical managed loads include EV chargers, electric water heaters, HVAC systems, heat pumps, pool equipment, spa heaters, and other nonessential electrical loads.

Benefits

• Lower installation costs
• Reduced need for utility upgrades
• Better utilization of existing electrical infrastructure
• Intelligent EV charging
• Future-ready electrical systems
• Enhanced grid flexibility

The Future of Smart Electrical Systems

As electrification accelerates, intelligent load management will become increasingly important. EMS technology enables electrical systems to be designed around controlled, real-time demand while maintaining compliance with NEC requirements.

Disclaimer

This article provides general information about NEC 2023. Always consult the adopted electrical code in your jurisdiction, applicable product listings, and the Authority Having Jurisdiction (AHJ) before applying any design or installation approach.