You've hit on a very common point of confusion and a crucial understanding for safely wiring office furniture systems with shared neutrals. Let's break down the issue and your options

Understanding the (2+2) Furniture Electrical System
(2+2) Configuration

This means the furniture power system has four circuits: two "sets" of circuits. Each set contains two 120V hot wires, a shared neutral, and a shared equipment grounding conductor.

Purpose

The shared neutral and ground reduce the number of conductors needed in the furniture whips, saving cost and space.

Key Concern

The shared neutral must be able to handle the combined current of both hot wires in its "set." If improperly wired, you risk overloading the neutral, leading to overheating and potentially fire.

Analyzing Your Situation & Contractor's Pushback

Your current approach of splitting the load across both (2+2) sets is generally acceptable and often preferred, provided it's done correctly and the total load on each shared neutral is managed.

Here's why your contractor's stance might be overly restrictive and how to address it:1. Contractor's Concern

His insistence on only using circuits from the same (2+2) set and requiring a 2-pole breaker is likely stemming from a fear of neutral overload and a desire for a unified disconnect. However, it limits your flexibility and can become problematic.2.

Why Your Approach Can Work (and is often better)



Load Balancing

Spreading the load across both (2+2) sets helps to balance the overall electrical system. It reduces the potential for voltage drops and uneven current distribution within the entire building.

Neutral Loading

By splitting the load, you reduce the potential current on each shared neutral. Consider this: If all six workstations were powered from the same (2+2) set, that shared neutral could see a significant current draw. Splitting the workstations across the two sets distributes this load.

Example

Say each workstation pod draws 5 amps. With your approach, each shared neutral only carries the current from 3 workstation pods, while the contractor's approach would require a shared neutral to carry the current from 6 workstation pods.3.

The Code & Shared Neutrals NEC 300.3(B) - Circuits in the Same Raceway

Requires all circuit conductors, including the neutral, to be run together in the same raceway or cable where the circuits are supplied by the same source.

This is the reason the furniture system uses shared Neutrals, to begin with. NEC 210.4(B) - Identification Required. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the circuit breaker where the circuit originates. This is not required if each individual circuit has ground fault protection.4. Addressing the Concerns and Ensuring Safe Wiring Load Calculation is Critical

This is the

MOST IMPORTANT step. You must accurately calculate the maximum load each workstation pod will draw. Include computers, monitors, task lights, and any other equipment. Provide this information to your contractor. NEC 220.14(I) - Receptacle Outlets; Non dwelling Units. This requires a load of no less than 180VA per outlet, or the receptacle's outlet rating. Neutral Sizing

Verify that the shared neutral in the furniture system is adequately sized to handle the calculated combined load of the two hot wires in that (2+2) set. The furniture manufacturer should provide this specification.

Breaker Size

Ensure the branch circuit breakers feeding the (2+2) sets are sized appropriately for the wiring and the calculated load.

Neutral Stability

The shared neutral must be properly connected at all points – at the panelboard, in junction boxes, and within the furniture system. A loose neutral can cause dangerous voltage fluctuations.5.

Addressing Contractor's Concerns



Education

Explain the load balancing benefits of your approach and emphasize that you understand the importance of accurate load calculations and proper wiring.

Documentation

Provide the contractor with a clear wiring diagram showing how the workstations are to be connected to the (2+2) sets. Include load calculations and breaker sizes.

Inspection

Ensure the installation is thoroughly inspected to verify all connections are tight and that the wiring matches your diagram.

In Summary:

Your approach of splitting the workstation pods across the two (2+2) sets is generally acceptable and can be beneficial for load balancing. However, accurate load calculations and proper wiring practices are essential to prevent neutral overload and ensure safety. Communicate clearly with your contractor, provide detailed documentation, and insist on a thorough inspection to ensure the installation meets code and your specifications. Flag for review