Dedicated 240V for central AC

[Mike Lamb]

Is it required to have a dedicated circuit breaker for 240V air conditioning.  Could you share the branch circuit with, let's say, an electric heater in the house, or a 240V garage receptacle?  A reference?

 

Edited June 23, 2017 by Mike Lamb

[Jim Katen]

Interesting question. 

The air conditioner installation instructions that I looked at did not specify dedicated circuits or individual circuits. 

The NEC doesn't specifically say that the AC needs to be on an individual circuit and, in fact, specifically allows the AC and the heating equipment to share a circuit. 422.12 (This assumes that they won't both be operating at the same time.) 

440.34 allows air conditioners to share conductors with "other loads," but it doesn't say how you handle the overcurrent protection. That's the sticking point. If you provide the "maximum" breaker, then there's really no room left for any significant additional load. 

[Marc]

The NEC doesn't offer any calculations to modify the manufacturer's engineered breaker size/fuse size/conductor size values on his multi-motor equipment so that additional loads can be served by the same circuit.  That should make it obvious that such circuit modifications in the field aren't allowed.

Edited June 25, 2017 by Marc

[Mike Lamb]

Thanks