All of the receptacles and switches in my house are 15 Amp. I recently had a new 200 Amp breaker box installed. All of the breakers are 20 Amps for these circuits. Do I have a problem?

No, what you have is fine, no safety problem, and done often.

Tk:

What if the wiring for the 15 A outlets is not 12 AWG?



Light switches are fine. The load never exceeds 15 A.

tk:

What if the wiring for the 15 A outlets is not 12 AWG?



Light switches are fine. The load never exceeds 15 A.

My first thought too. The breakers should be properly sized for the circuit wiring. What size cable are all these 20A breakers on?

Maybe I'm assuming something I shouldn't be.

Your rating of tk's answer was correct. I have rated him too recently to rate him again. If you don't have anything with a 20 amp plug on it, you don't need 20 amp outlets. The 20 amp circuits just allow you to run more things at once.

I guess I am assuming the work was done properly, and am being a bit too trusting.

Kisses point is have it checked to be sure is wise.

It is odd to have an older panel upgraded and be able to have all #12 wire for 20 amp breakers. Were they all 20 amp fuses before?

If this was just changed and the wrong size breakers are installed, this installer deserves to be dealt with severely.

The maximum breaker size is, in part, determined by wire gage, length and service factor.

The minimum breaker size is generally determined by the load unless the above is lower.

Initial assumptions are #14 for 15 Amp circuits.
#12 for 20 amp circuits

So, if the breaker connects to #14 it should be 15 amp. If the breaker is connected to #12 wire, it can be 20 amps subject to the above rules.

It's entirely possible that the installer got a box with pre-installed breakers.

I'd also check if any of the breakers are GFCI and/or arc fault. Bedrooms and living rooms require arc fault. GFCI's in wet areas like outside and the bathroom and near the sink in the kitchen. These breakers require a connection to neutral, so they should be easily identified.

Seems like a competent inspector would find it.

Bedrooms only need AFCI, and not just because the panel was changed. It cannot be assumed the house wiring is such that a circuit is only for bedrooms.

Could be minimal inspection , and inspectors usually are held harmless for what is missed.

Length never affects branch circuit breaker size.