You've hit on a really interesting point about the evolution of engineering practices and how legacy beliefs can persist. Let's break down the arguments for and against daisy-chaining fixtures in the contexts you've described (schools, courts, hospitals, government facilities) after consulting the NEC

Arguments Against Daisy Chaining (and why they might have been stronger in the past):
Interruption of Service

This is the primary concern. A fault, maintenance, or removal of one fixture knocks out all downstream fixtures. While you're right that work shouldn't be done live, things happen, and isolating individual fixtures is generally safer, especially in critical environments like hospitals. This applies directly to the NEC because as noted in article 210.4(B) in the NEC (2023), multiwire branch circuits shall supply only listed utilization equipment. This generally means that the equipment in question is not intended to be daisy chained.

Voltage Drop

Each connection introduces resistance. With multiple fixtures on a single run, voltage drop can become significant, leading to dimming, reduced performance, and potential damage to downstream ballasts/LED drivers. In the past, with less efficient lighting technology and potentially less stringent wiring practices, this was a bigger issue.

Fault Current Coordination

In a daisy-chained system, a fault at the end of the line could have a higher impedance, potentially limiting the available fault current. This could hinder the proper operation of overcurrent protective devices (OCPDs), increasing the risk of arc flash and fire. This is still a valid concern, even with modern OCPDs, especially on longer runs.

Maintenance and Troubleshooting

Finding and fixing a problem in a daisy-chained system can be more time-consuming. Isolating the faulty fixture is more complex.

Code Compliance (Historically)

In the past, local codes and interpretations might have been stricter regarding the number of fixtures on a single circuit and the types of wiring methods allowed for daisy-chaining.

Building Resiliency

From your own write up, daisy chaining can create points of failure that could easily be eliminated.

Arguments FOR Daisy Chaining (and why they are more relevant now)



Cost Savings

Less wiring, conduit, and labor translate directly to lower initial costs. This is especially attractive in large projects with hundreds or thousands of fixtures.

Ease of Installation (potentially)

With modern pre-wired fixtures and quick-connect systems, daisy-chaining can be faster and easier than running individual homeruns for each fixture. This is a BIG "if" and depends heavily on the specific fixtures and installation methods.

Flexibility in Layout Changes (potentially)

If you are using track lighting or modular systems that are designed to be daisy-chained, then it makes sense. If, say, a tenant in an office space wants to add lighting, there is already a way to handle the wiring to new fixtures without running wire back to the electrical panel.

Standardization and Manufacturing

Many modern LED fixtures are designed with daisy-chaining in mind, incorporating built-in connectors and overcurrent protection for downstream fixtures.

Why the Shift in Perception? Improved Lighting Technology

LEDs are more efficient and less susceptible to voltage drop than older technologies like fluorescents.

Better Wiring Practices

Modern wiring methods, better insulation, and stricter code enforcement have reduced the risk of faults and failures.

Sophisticated Fixture Design

Many modern fixtures incorporate features like built-in overcurrent protection and voltage regulation, making daisy-chaining safer and more reliable.

Pre-fabricated Wiring Systems

Modular wiring systems with pre-wired cables and connectors make daisy-chaining simpler and less prone to errors.

Where Daisy Chaining Might Be Acceptable Today (with caveats)



Fixtures Specifically Designed and Listed for Daisy-Chaining

If the manufacturer has designed the fixtures for daisy-chaining and provides clear instructions and limitations, and the fixtures are listed for this purpose, it's a stronger argument. NEC 410.137 and 410.138 cover requirements for luminaire wiring.

Low-Voltage Lighting Systems

Low-voltage systems (e.g., 24VDC LED lighting) are inherently safer and less susceptible to voltage drop.

Areas with Low Occupancy and Non-Critical Functions

In areas where a temporary loss of lighting is less critical (e.g., storage rooms, non-patient care areas in hospitals), daisy-chaining might be considered, but still with careful engineering review.

Why You Should Likely Stick to Your Current Spec (and what to consider if you want to change it)



Risk Aversion

Your current spec represents a conservative approach that minimizes risk and ensures reliable lighting in critical environments.

Liability

As the consulting engineer, you are responsible for the design. Changing a long-standing practice carries risk.

Owner Preference

Your clients (schools, courts, hospitals) may have their own preferences and historical experiences that influence their acceptance of daisy-chaining.

Operational Requirements

Maintenance and operational staff are used to troubleshooting problems within the framework of homerun wiring.

If you do want to consider allowing daisy-chaining, here's what you need to do


Research Thoroughly

Investigate the specific fixtures you are considering. Get detailed specifications, including maximum daisy-chain length, voltage drop calculations, and overcurrent protection features.2.

Review Local Codes

Confirm that daisy-chaining is permitted under local codes and interpretations.3.

Perform Voltage Drop Calculations

Calculate the voltage drop for the longest anticipated daisy-chain run. Ensure it is within acceptable limits.4.

Specify Overcurrent Protection

Ensure that the fixtures and wiring are adequately protected by overcurrent protective devices.5.

Detailed Drawings

Your shop drawings should provide detailed diagrams that the installers have to follow in the field so that the fixtures are connected correctly.6.

Communicate with Installers

Discuss the proposed change with electrical contractors to get their feedback and ensure they understand the requirements.7.

Update Your Specifications Carefully

Your specification needs to address the above topics and very clearly explain which fixtures are* allowed to be daisy-chained and under what conditions. Be clear what's disallowed.8.

Consider a Pilot Project

Before implementing daisy-chaining on a large scale, consider using it on a small pilot project to evaluate its performance and identify any potential issues.

Conclusion:

While modern lighting technology and wiring practices have reduced some of the risks associated with daisy-chaining, it's still generally not recommended for critical environments like schools, courts, and hospitals. The potential for interruption of service, voltage drop, and fault current coordination issues outweigh the potential cost savings. In your role as a consulting engineer, maintaining a conservative and reliable approach is usually the best course of action. However, if you choose to consider daisy-chaining, do so cautiously and with thorough research, calculations, and communication. Most importantly, make sure to stay grounded in what the NEC is telling you. Flag for review