Okay, it sounds like you're dealing with a common situation: light poles with both 277V lighting and 120V receptacles. Here's a breakdown of the issues and best practices, focusing on the underground boxes (pull boxes, handholes) that house the wiring

The Core Issue: Voltage Separation
NEC Concerns (National Electrical Code)

The NEC is very clear about separating different voltage systems to minimize the risk of accidental contact, arc-faults, and potential hazards. The general idea is to prevent someone working on the 120V receptacle circuit from accidentally contacting the 277V lighting circuit.

Safety

Mixing voltages in a confined space increases the risk of accidental shock, especially during maintenance or repairs.

Why Separate Voltages in Underground Boxes?1. Safety for Technicians

Minimizes the risk of accidentally touching a live 277V wire while working on the 120V outlet.2.

Clear Identification

Separating circuits makes it easier to identify and trace wires, reducing the chance of mistakes.3.

Code Compliance

Mixing voltages in a single, non-divided box could violate NEC requirements in many situations.

Your Options and Best Practices


Dedicated Underground Boxes



Ideal Solution

The cleanest and safest approach is to use separate underground boxes for the 120V and 277V circuits. This completely eliminates the risk of voltage mixing. You'd have one box dedicated to the 120V receptacle wiring and another box dedicated to the 277V lighting wiring.2.

Underground Boxes with Barriers (Your Quazite Solution)



Acceptable, with Strict Adherence

Using a Quazite or similar underground box specifically designed with a barrier is a viable option if you adhere to these points:

Listed and Labeled

The box must be listed and labeled for this purpose (mixed voltage separation). Check the manufacturer's documentation carefully.

Proper Barrier Installation

The barrier must be installed correctly according to the manufacturer's instructions. Don't skip steps or assume it's obvious.

Dedicated Compartments

The barrier must create fully separate compartments within the box. The 120V wiring should be entirely isolated from the 277V wiring.

Secure Terminations

Make sure that all wire connections are secure and properly insulated within their respective compartments.

Clearly Marked

The box should be clearly marked to indicate that it contains multiple voltage systems.

Voltage separation minimum distance

Consult your local code.3.

Conduit as a Barrier



The 120v and 277v wires enter in PVC conduit is a form of a barrier.

NEC Considerations (Consult a Qualified Electrician)



Article 300 of the NEC

This covers general wiring methods and often has requirements related to voltage separation.

Article 314 of the NEC

This covers junction boxes, pull boxes, and handhole enclosures. Pay attention to the rules on box fill and conductor separation.

Local Amendments

Be aware that your local jurisdiction may have additional amendments to the NEC that are more stringent.

General Recommendations



Consult with an Electrical Engineer or Licensed Electrician

This is crucial! They can review your specific situation, local codes, and the manufacturer's specifications for the underground box to ensure compliance and safety.

Documentation

Keep thorough documentation of the installation, including manufacturer's instructions, wiring diagrams, and inspection reports.

Grounding

Proper grounding is essential for both the 120V and 277V circuits.

In summary:

While it's possible to bring 120V and 277V into the same underground box if* the box is designed and listed for that purpose with a properly installed barrier, the best practice is often to use separate boxes. Safety and code compliance are paramount. Don't cut corners on this. Always consult with qualified professionals. Flag for review