You're right to be concerned about conflicting interpretations. Here's a breakdown of the GFCI requirements under the 2018 IRC and 2017 NEC, focusing on common residential scenarios

Understanding the Basics
GFCI (Ground Fault Circuit Interrupter)

A fast-acting circuit breaker that detects small imbalances in current, indicating a potential ground fault (electricity leaking where it shouldn't). They are designed to quickly shut off power to prevent electric shock.

IRC (International Residential Code)

Primarily covers building-related aspects, but refers to the NEC for electrical specifics.

NEC (National Electrical Code)

The definitive standard for safe electrical installation. The IRC adopts portions of the NEC.

2017 NEC & 2018 IRC GFCI Requirements (Relevant Sections)



NEC 210.8(A): Dwelling Units - All 125-Volt, 15- and 20-Ampere Receptacles in Specified Locations

This is the key section that drives most GFCI requirements in homes. It requires GFCI protection for all 125V, 15A and 20A receptacles installed in the following locations:

Bathrooms

Receptacles serving bathroom countertops.

Garages, and also accessory buildings that have a floor located at or below grade Outdoors

All outdoor receptacles.

Crawl Spaces

At or below grade level.

Unfinished Basements

This one can be tricky! GFCI protection is required for receptacles in unfinished basements.

Kitchens

Receptacles serving kitchen countertops

Sinks

Within 6 feet (1.8 m) of the outside edge of sinks.

Boathouses Laundry areas Damp and Wet Locations

Other areas that are considered wet or damp, which is subject to interpretation.

NEC 210.8(D): Specific Appliances

This section often gets overlooked. GFCI protection is also required for specific appliances:

Dishwashers

In dwelling units.

Electric ranges and dryers (240V)

Only when specific manufacturers instructions require it.

NEC 210.8(F): Outdoor Outlets All outdoor outlets, regardless of voltage, must be GFCI protected when readily accessible.

Your Specific Questions


120 Volt 15-20 Amp Branches

Generally, your understanding is correct. Any 120V, 15A or 20A receptacle outlet in the locations listed in NEC 210.8(A) (bathrooms, outdoors, kitchens near sinks, etc.) must be GFCI protected. This applies regardless of accessibility. The inspector requiring GFCI on everything is likely misinterpreting or over-applying the code, unless everything is in one of the listed locations.2.

120 Volt 30 Amp (RV Plug)

This is where things get less clear, and the NEC has changed in recent years.

NEC 210.8(F) does require GFCI protection for all outdoor outlets, regardless of voltage, when readily accessible. Therefore, if the RV receptacle is outdoors and "readily accessible", it does need GFCI protection under the 2017 NEC. "Readily Accessible" generally means capable of being reached quickly for operation without climbing over obstacles, removing obstacles, or using portable ladders.3. 240 Volts

For standard 240V receptacles (like those for a dryer), GFCI protection is generally not required unless specifically required by the manufacturer's instructions of an appliance plugged into it.

NEC 210.8(F) requiring GFCI for all accessible outdoor outlets would require GFCI for outdoor 240v receptacles.4. Hardwired Furnace

Hardwired appliances (like a furnace) are typically not required to have GFCI protection. They are usually on dedicated circuits. However, a 120V receptacle outlet serving the furnace (for maintenance) located in a basement would require GFCI protection.

Important Considerations



Local Amendments

Your county may have local amendments to the NEC that are more restrictive than the national code. This is a critical point. Ask the inspectors (or your permitting office) if there are any local amendments to the 2017 NEC regarding GFCI requirements. This is the most likely reason for the conflicting interpretations.

AHJ (Authority Having Jurisdiction)

Ultimately, the final decision rests with the AHJ (in your case, the county inspectors).

Manufacturer's Instructions

Always check the manufacturer's instructions for appliances. They may require GFCI protection, even if the code doesn't specifically mandate it.

Recommendations


Obtain Written Clarification

The best course of action is to request a written clarification from the county's building department (permitting office) about their interpretation of GFCI requirements, specifically referencing the 2017 NEC sections. Ask if there are any local amendments. A written interpretation will be invaluable.2.

Escalate if Necessary

If the inspectors continue to disagree, ask to speak with their supervisor or the chief building official for the county. A consistent interpretation is essential.3.

Err on the Side of Caution (But Document)

If you're unsure, installing GFCI protection is always safer. However, document the conflicting instructions and the fact that you installed GFCI protection based on one inspector's interpretation, even if you believe it's not explicitly required by the code.4.

Careful Placement

Be strategic about where you place GFCI receptacles. Avoid placing them in areas prone to nuisance tripping (e.g., where motors or older appliances cause frequent false alarms). You can use a GFCI breaker to protect an entire circuit, rather than individual receptacles, which can sometimes be more practical.5.

Readily Accessible Definition: The definition of readily accessible is important for exterior receptacles.6. Ask about exceptions There are some exceptions to the GFCI rules.7. AFCI protection AFCI protection is different from GFCI, so make sure to not get the two confused.By gathering written clarification from the county and understanding the specific NEC sections, you can address the conflicting interpretations and ensure your electrical installation complies with the code and prioritizes safety. Good luck! Flag for review