Okay, this is a common and important question in electrical work, especially when dealing with modifications and potential inspections. Here's a breakdown of why changing the breakers is generally required, and the considerations involved

Why You Likely Must Change the Breakers to 15A:
Code Compliance (NEC)

The National Electrical Code (NEC) is very clear on this. Breakers are designed to protect the circuit wiring, not the devices plugged into the circuit. If the wiring is now only rated for 15A, then the overcurrent protection (the breaker) must be 15A. This is to prevent the wiring from overheating and potentially causing a fire.

Wire Ampacity

The reason the original circuits might have had 20A breakers could have been that they were wired with 12 AWG (American Wire Gauge) wire, which is rated for 20A. If the wiring has been changed to 14 AWG wire, which is rated for 15A, then the breaker must be downsized.

Safety

The primary purpose of a breaker is to protect the wiring. A 20A breaker on a 15A circuit allows the possibility of overloading the wiring to a dangerous level before the breaker trips. This creates a fire hazard.

Inspection

Inspectors will scrutinize this. It's a very basic and fundamental aspect of electrical safety. Leaving a 20A breaker on a circuit that now requires a 15A breaker is a red flag and will likely result in a failed inspection.

Manufacturer Listing/Instructions

Electrical devices are listed for safe use at their specified amperages. You're potentially voiding the listing and creating a safety hazard if you're over-fusing a circuit.

When Leaving a 20A Breaker Might Be Acceptable (But Highly Unlikely in This Scenario)

There are very specific and limited circumstances where a larger breaker might be allowed, but these almost certainly don't apply to your situation:

Dedicated Appliance Circuits

If a circuit is dedicated to a specific appliance and the appliance manufacturer's instructions specifically allow or require a larger breaker (e.g., for a motor-driven appliance with a high inrush current), and the wiring is sized appropriately for the larger breaker, then it might be permissible.

This is extremely rare and requires documented evidence. Motor Circuits

Motor circuits sometimes require overcurrent protection sized based on motor nameplate data and NEC tables. But even then, the wiring must be sized accordingly.

Code Exceptions (Very Specific)

There are very narrow exceptions in the NEC that might allow for a slightly larger breaker in specific circumstances. These are complex and require careful interpretation of the code.

What to Do Now


Verify the Wire Gauge

Double-check the gauge of the wiring in the affected circuits. This is the most important step. Turn off the breaker and look at the markings on the cable sheath (the outer plastic covering). You'll usually see something like "14/2 w/G" or "12/2 w/G". "14" means 14 AWG, "12" means 12 AWG.2.

Confirm the Circuit Requirements

Review the documentation for the new circuits to confirm that they are indeed intended to be 15A circuits.3.

Change the Breakers

If the wiring is 14 AWG and the circuits are intended to be 15A, change the breakers to 15A.

This is the safest and most code-compliant approach.4. Document Everything

Keep detailed records of the changes you've made, including the wire gauge, the breaker sizes, and any relevant documentation.

Important Considerations



"New Work, Higher Scrutiny"

You're absolutely correct that new work is scrutinized more closely. Inspectors will be looking for proper sizing of breakers and wiring.

Liability

If you leave the 20A breakers in place and there's a fire caused by overloaded wiring, you could be held liable.

Professional Advice

If you're unsure about any aspect of this, consult with a qualified and licensed electrician. It's always best to err on the side of safety.

In Summary:

In almost all cases, you must* change the breakers to match the ampacity of the wiring and the circuit requirements. It's a fundamental safety principle and a requirement of the NEC. Leaving 20A breakers on 15A circuits is a significant safety hazard and will likely fail inspection. Always prioritize safety and code compliance. Flag for review