Okay, this is a common challenge when upgrading services while keeping a home habitable. Here's a breakdown of your options, considerations, and a preferred approach

Understanding the Code (NEC 590)

You're correct to focus on NEC 590 (Temporary Installations). Specifically, 590.6(A) is the section that governs GFCI protection. The key language is about receptacle outlets. 590.6(A)(1)

GFCI protection is required for "all 125-volt, single-phase, 15-, 20-, and 30-ampere receptacle outlets that are not a part of the permanent wiring of the building or structure..." This typically applies to extension cords and temporary power strips used during construction.

590.6(A)(2)

"All receptacle outlets that are existing or installed as part of the permanent wiring of the building or structure and are used for temporary power shall have ground-fault circuit-interrupter protection for personnel." This is the section causing your current dilemma.

Analyzing Your Options & Challenges1. 100A GFCI Breaker / 60A GFCI Breaker



Challenge

100A GFCI breakers are rare and very expensive. Also, if they exist, they might not be readily available. This is not a practical solution. You are more likely to find a 60A GFCI breaker, but this may not be enough to power the home with AC and standard loads.

Problem

Overlapping GFCI protection (the 60A GFCI breaker tripping due to existing GFCI receptacles).2.

Standard 100A Breaker & Replacing Branch Breakers with GFCIs



Pros

Technically code-compliant.

Cons

Labor-intensive and expensive. You'd need to replace every 15A, 20A, and 30A breaker with a GFCI breaker. This can be difficult as some older panels are not easily retrofitted with GFCI breakers.

Problem

Existing GFCI receptacles might still cause nuisance tripping if the GFCI breakers are not functioning properly.3.

Using a Listed Temporary Power Panel with GFCI Protection



Pros

A more engineered and safer solution.

Cons

Cost and availability of the right-sized temporary panel.

A Preferred Approach: Minimizing Reliance on Existing Outlets for Temporary Power

The best approach is to minimize the use of existing receptacles for temporary power during the re-siding. Here's a strategy:1. Install a Temporary Service Panel with GFCI Protected Receptacles

This temporary panel should be installed near your temporary meter. This panel should include at least 2 20A 125V GFCI receptacles and a 30A 240V receptacle.2.

Run a Limited Number of Dedicated Circuits

If absolutely necessary, feed a few circuits from the existing panel only to power essential appliances (refrigerator, maybe a few lights). Ideally, these should be circuits that don't have existing GFCI protection. To meet code, those circuits would be wired with 12/2 or 12/3 with ground cable, and terminated into the temporary panel with the appropriate overcurrent protection. This cable should be readily accessible for inspection purposes.

This is the key

You're NOT using all the existing receptacles as your "temporary power." You're only using a few designated circuits.3.

Dedicated Temporary Wiring for Specific Needs

If they need temporary lighting for a specific area, run a temporary power cord from the temporary panel and set up a temporary light.4.

Communication

Have a clear conversation with the homeowners. Explain that for the duration of the siding work, their reliance on existing outlets will be limited. Emphasize that the goal is to keep the house habitable, not to provide uninterrupted full electrical service.

Steps to Implement the Preferred Approach1. Detailed Load Calculation

Determine the minimum essential load required to keep the house habitable. This should include the refrigerator, a few lights, and perhaps one or two other critical appliances.2.

Temporary Service Panel

Install a temporary service panel with the appropriate GFCI-protected receptacles.3.

Careful Wiring of Essential Circuits

If you must use existing circuits, carefully identify circuits that do not have existing GFCI protection (e.g., living room lighting).4.

Clear Labeling

Clearly label all temporary wiring and receptacles.5.

Grounding and Bonding

Ensure proper grounding and bonding throughout the temporary setup.6.

Inspection

Schedule an inspection of the temporary service before energizing it.

Why This Approach Works Minimizes Code Exposure

By limiting reliance on existing outlets, you minimize the amount of existing wiring that needs GFCI protection.

Practical and Cost-Effective

This is generally less expensive and less labor-intensive than replacing every breaker with a GFCI.

Safety

A dedicated temporary service panel with GFCI protection provides a safer and more reliable solution.

Important Considerations Local Codes and AHJ

Always check with your local authority having jurisdiction (AHJ) for any specific requirements for temporary services. They might have additional rules or preferences.

Homeowner Expectations

Be very clear with the homeowners about the limitations of the temporary power setup. Managing expectations is crucial.*

Safety First

Prioritize safety in all aspects of the temporary installation.

In summary, avoid trying to make every existing receptacle GFCI-protected. Instead, provide a dedicated temporary service with GFCI protection and run a limited number of dedicated circuits for essential appliances. This approach balances code compliance, practicality, and safety. Good luck! Flag for review