Common Problems with Oversized Breakers
by JD Greewell
What I find quite regularly are oversized breakers for condenser units and clothes dryers.
Clothes dryers should almost universally be on a breaker no larger than 30 amps. Most dryers have two heating coils that draw 10 Amps each. There are smaller stackable units that have only one coil and draw only 13 Amps including the drum motor. The vast majority of electric clothes dryers have two heating elements. Those with two elements draw about 24 Amps maximum. The dryer should normally not be on a wire size larger than a number 10 copper conductor.
Having a clothes dryer on a 40 Amp breaker is improper. The dryer could overheat while the associated oversize breaker would not trip until there was a dead short creating a fire hazard. There is no violation to have a clothes dryer on a Number 8 copper conductor.
Whenever I find a small one-element clothes dryer, I caution the client to consult a qualified electrician to consider reducing the 30 Amp dryer breaker to none larger than 20 Amps because the unit normally will never draw more than 13 Amps in operation.
Condensers, both for cooling and for heat pumps, have the data plate located on the condenser shell. That data clearly states the Maximum and Minimum Circuit Amperages allowed by each manufacturer. These specifications become code even though they are rarely enforced specifically.
For example, see the photo below:
This condenser requires a minimum wire size rated for 19.2 Amps which would allow for a #12 wire. That #12 wire could be connected to a 30 Amp breaker and be in full compliance with code but it cannot be connected to a 35 or 40 Amp breaker.
Far too many HVAC contractors are not licensed electricians therefore they cannot change the breaker in the panel so the often overlook leaving a new condenser on the existing breaker in the main panel. Leaving the condenser on an oversized breaker can void the manufacturer’s warranty and does not comply with the installation requirements thus violating code provisions to follow the manufacturer’s instructions.
