I had a home built with a 1 year warranty. It is still under warranty. The electrician didn't install a big?

enough breaker in the master bathroom and the breaker jumps when I use my hair dryer. The builder says this is not under warranty since I had a heater and a chandelier installed. This was all in the plan from the beginning. I did not make any changes. Whose responsiblity is it to pay for the electrical work now?