Hvac Circuit Breaker Sizing

In need of evaluation and repair by qualified electrician.

Hvac circuit breaker sizing.

The air conditioner specification plate calls for maximum breaker size of 20 amp. The over current device fuse or circuit breaker must be sized for the ampacity of the service drop and available fault current. If triplex is used table 310 16 must be used as directed by nec article 321 5. Ocpd size 100 of noncontinuous load 125 of continuous load.

If you see a normal household plug on it with three straight prongs assume 120 v of power requirement. Take a look at the lennox air conditioning condensing unit tag on page 19. A 30a circuit breaker can safely carry the exact 30a current but nec suggests 80 as a safe current limit as compared to the rated current. The circuit breaker also needs to be large enough to support the minimum circuit ampacity which for this example would be a circuit breaker rated for at least 34 amps which means we d jump up to.

Difference between circuit breaker and isolator disconnector circuit breaker size calculation for continuous non contentious load. The first three all specify the same requirement. As circuit breakers cbs and overcurrent protection devices ocpd are designed for 100 rated current i e. If you don t see a voltage requirement check the plug on the air conditioner.

Breaker size based on wattage the size of a breaker is determined by the amp draw. However typically electric furnaces require a draw between 60 and 80 amps. If you see a plug with two diagonal prongs and one straight prong under it assume 240 v of power requirement. By multiplying the volts by amps you will receive total wattage.

This means it is allowable to install this unit on a circuit breaker rated at 50 amps and a conductor rated at 28 6 amps according to the nec s nfpa 70. Observed that the circuit breaker for ac unit is over sized 50 amp. The service drop conductors must be sized from table 310 17. 210 22 c 220 3 a 220 10 b and 384 16 c all relate to the sizing rules for overcurrent protective devices ocpds.

Notice that the mca is 28 6 amps and the maximum fuse or circuit breaker is 50 amps.