We are adding a room to our home. The builder says that we have 10ga wire going to the existing lights and outlets then back to a 15amp breaker. He wants to replace the wire with 14ga. He says the 10ga is a fire hazard and will cause the lights to burn out faster. Is this true? Or can we leave the 10ga in place?

Maybe he means old BX getting overheated in insulated ceilings? I'd replace it.

It hasn't been overheating. He just saw it and said we need to replace it because it is 10ga and will burn out our lights faster or any other appliances that doesn't require that high of a gauge wire.

It hasn't been overheating. He just saw it and said we need to replace it because it is 10ga and will burn out our lights faster or any other appliances that doesn't require that high of a gauge wire.

He speaks an untruth.

10 AWG cable is listed for 30 amps.

Normally, you would use a 15 Amp breaker on a 14AWG cable.

It is perfectly fine to use a 10 AWG with a 15 amp breaker. Regardless of the size difference between the two cables, the breaker is going to limit the current flow to 15 amps.

it hasn't been overheating. He just saw it and said we need to replace it because it is 10ga and will burn out our lights faster or any other appliances that doesn't require that high of a guage wire.
The guy is a nut job!

WHY would you have #10 on a lighting circuit anyway? Is it aluminum? That would change EVERYTHING.