Okay, let's break down the Massachusetts amendment to NEC 210.12 and the issue of AFCI protection for exterior receptacles. I'll give my interpretation, but remember, interpretations can vary, and ultimately the Authority Having Jurisdiction (AHJ) (i.e., your local electrical inspector) has the final say.

Here's a hypothetical example of the likely Massachusetts amendment (since you didn't provide the exact text)

Hypothetical Example:"210.12(A) Dwelling Units. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices installed

in dwelling units shall be protected by arc-fault circuit interrupter protection as required in 210.12(A)(1) through (6).(1) Kitchens(2) Family Rooms(3) Dining Rooms(4) Living Rooms(5) Parlors(6) Bedrooms"The Core Issue: The Word "In" and Receptacles

The confusion hinges on the interpretation of "in" a dwelling unit. Does an exterior receptacle, even if physically attached to the house, fall inside the scope of being in the dwelling unit?Here's my interpretation, and the arguments that support it



Literal Interpretation

A strict, literal reading of "in" would suggest that anything physically outside the dwelling unit's envelope (exterior walls, roof) is not covered by the AFCI requirement. This interpretation focuses on the physical location of the receptacle.

Purpose and Intent (Less Likely)

AFCI protection is primarily intended to reduce the risk of fires inside the dwelling, where people sleep and live. A faulty receptacle outdoors is considered by many to pose a lower risk to occupants sleeping in the residence, even though it might present other hazards (e.g., shock, fire in the yard). This line of thinking is less likely to be valid for this specific interpretation of the code.

Arguments for Requiring AFCI Protection (and why inspectors might lean this way)



Part of the Branch Circuit

The receptacle, even if outside, is still fed by a branch circuit originating inside the dwelling. Some argue that the entire branch circuit must be protected, regardless of where the last outlet is located. This is a very common argument since the branch circuit originates "in" the dwelling unit as stated in the amendment.

Accessibility and Use

If the receptacle is easily accessible and likely to be used for things that introduce arc-fault risks (power tools, holiday lights, etc.), some inspectors might be more inclined to require AFCI protection.

Safety and Precedent

Requiring AFCI protection provides the highest level of safety, and avoids potential ambiguity in future interpretations.

Future Use

If the outside receptacle is removed at some point in the future, and the branch circuit is extended, AFCI protection would be required if it was located on an interior wall.

Local Amendments

Even though you state that this is a Massachusetts amendment, double check that there isn't other more local amendments that could change this interpretation.

Arguments Against Requiring AFCI Protection



Literal Interpretation of "In"

The most obvious argument, as stated above, is that it is not physically in the dwelling.

Cost

AFCI breakers/receptacles are more expensive. Requiring them for exterior outlets increases the cost of the installation.

How to Approach the Situation


Talk to Your Inspector First

Before doing any work, contact the electrical inspector for the jurisdiction where you are working. Get their interpretation in writing, if possible. This is the most important step.2.

Cite Code and Reasoning

Be prepared to discuss your interpretation of 210.12 and your reasoning. You can use the arguments for and against AFCI protection that I've outlined above.
3.

Documentation

Keep thorough records of your conversations with the inspector, including dates, names, and the substance of the discussion.4.

Follow the Inspector's Decision

Ultimately, you must comply with the AHJ's interpretation. If you disagree, you can appeal through the proper channels, but in the meantime, follow their ruling.

Specific Considerations When Replacing a Receptacle



GFCI Protection

Remember that exterior receptacles must be GFCI protected (210.8). AFCI and GFCI protection are different and serve different purposes. You may need a combination AFCI/GFCI breaker or a GFCI receptacle with AFCI protection.

Existing Installation

If the receptacle being replaced was not originally AFCI protected, the inspector may be more lenient, especially if the original installation was compliant with the code at the time. However, this is not a guarantee.

In summary:

The interpretation of "in" is the key point of contention. While a strict, literal reading might suggest AFCI protection is not required for exterior receptacles, the inspector could reasonably argue that the receptacle is part of a branch circuit originating in the dwelling and/or the intent of the code is to protect the branch circuit. The best approach is always to communicate with the AHJ before* starting the work to get a clear understanding of their requirements. Good luck! Flag for review