Performed heater tune-up on a Carrier gas furnace system. Checked the electrical, mechanical and performance systems of the unit. Cleared, cleaned, flushed and treated the drain line and cleaned the exterior of the furnace. I did find the main breaker for the outdoor system is oversized. The current breaker is a 30A two pole Cutler Hammer and the system needs a maximum 25 amp breaker. Presented repair options to the customer. No other major issues were found. The system is running at completion of service.