You've presented a reasonable and well-articulated argument. Let's break down NEC 110.26 and how it applies to your situation of a 30A disconnect for a water heater

Understanding NEC 110.26 and Your Arguments

NEC 110.26 deals with spaces about electrical equipment. The intent is to provide sufficient space for safe operation and maintenance. The key is understanding which parts apply based on the equipment's characteristics. NEC 110.26(A) - Working Space

This section requires specific clearances (3 ft x 30" x 6.5 ft) if the equipment is likely to require examination, adjustment, servicing, or maintenance while energized.

Your Argument

You argue (correctly, in my opinion) that a simple disconnect is not intended to be worked on live. Its primary function is to de-energize the water heater for maintenance. Therefore, the working space requirements of 110.26(A) do not automatically apply. The critical phrase here is "likely to require examination, adjustment, servicing, or maintenance while energized." A disconnect is a safety device, intended to be off when work is performed.

NEC 110.26(E) - Front Working Space

This section deals with "switchboards, switchgear, panelboards, or motor control centers."

Your Argument

You argue that a small, simple disconnect switch, even though it has the word "switch" in its name, is not switchgear. You correctly point to the Article 100 definition of switchgear, which implies a larger, more complex assembly. A disconnect switch doesn't fit that definition. Therefore, 110.26(E) does not apply.

Conclusion and Rationale

Your reasoning is sound. Here's a summary: The 30A disconnect for a water heater is not switchgear, a switchboard, a panelboard, or a motor control center. It's a simple disconnecting means. 110.26(E) does not apply. The disconnect is not designed or intended to be worked on live. Its purpose is to provide a safe means to de-energize the circuit. Therefore, the working space requirements of 110.26(A) are not automatically required. If there is no intention, need, or likelihood of it being worked on while energized, the working space requirements for energized equipment do not come into play.

Treating it Like a Common Switch

Your conclusion that it can be treated like a common switch is a good way to think about it. While not explicitly addressed in the NEC, consider this; The disconnect, when closed, is essentially a switch. When opened, its a disconnect. The working space requirements for a common switch are not explicit, and generally don't require the full 3 ft x 30" x 6.5 ft clearance as per 110.26(A).

Important Considerations & Caveats1. Local AHJ (Authority Having Jurisdiction)

The AHJ has the final say. It is always prudent to discuss your interpretation with your local electrical inspector. They may have specific local rules or interpretations.2.

Accessibility

The disconnect must be readily accessible (NEC 110.26(A)(1)). This means it shouldn't be blocked or difficult to reach. However, readily accessible does not mean the full 3' x 30" working space is required if energized work is not intended.
3.

Manufacturer's Instructions

Always consult the manufacturer's instructions for the disconnect switch. They may have specific recommendations or warnings regarding installation and access.4.

Good Electrical Practice

Even if the NEC doesn't require the full working space, it's always a good idea to provide enough room to safely operate the disconnect and perform basic visual inspections. Don't jam it into an inaccessible corner.5.

Future Work

If there is any reasonable expectation that someone might need to work on the disconnect while energized (e.g., troubleshooting a wiring problem within the disconnect itself), then providing the working space might be justified. However, this is not the typical scenario.6.

Water Heater Service

While the disconnect may not need live work, the water heater itself might. Consider the accessibility of the water heater itself, not just the disconnect.

In summary, your interpretation is likely correct. The 30A disconnect switch for a water heater, serving primarily as a disconnecting means, doesn't automatically require the full working space outlined in NEC 110.26(A) or (E).

Always prioritize safety and consult with the AHJ. Flag for review