Dedicated A.C. Circuit - Air Conditioner Disconnect




• A.C. Disconnect

Air Conditioners require a means of disconnect at the electrical panel and a disconnect outside. An A.C. disconnect allows for a connected A.C. system to be disconnected from the power source. An air conditioner disconnect is required by code as a safety precaution to allow for a technician to diconnect power while servicing the air conditioner unit. From the electrical panel to the disconnect a feeder wire is needed. The specifications usually require copper wire for the unit itself. THHN copper is used from the disconnect to the unit ran through electrical nonmetallic tubing to protect the wires from damage.

Requirements for air-conditioning equipment disconnecting means are found in 440.14 and 440.13. The requirements and reasons for disconnects at air-conditioning and refrigeration equipment are basically the same. The decision whether or not to use the rules in Article 440 rather than Article 430 is related to the type of motor employed within the equipment. Basically, if the motor or equipment incorporates a hermetic refrigerant motor compressor, then the rules in 440.14 apply. Both types of motors are used with air-conditioning and refrigeration equipment and systems, so it is important to establish which Code article and rules apply for a given installation.

If the air-conditioning equipment incorporates or is driven by a standard motor, meaning a motor that is not hermetically sealed, then the rules in 430.102 have to be applied. It is helpful to visit the definitions in 440.2 for additional clarification on hermetic refrigerant motor compressors. Section 440.3(A) clearly indicates that if the equipment does not have a hermetic refrigerant motor compressor, then 440 does not apply and reference is made back to Articles 422, 424, or 430 as applicable. An example of refrigeration equipment falling under the scope of Article 430 is the typical fan coil unit installed in a walk-in refrigerator or freezer. The disconnecting means would need to be provided for such equipment in accordance with 430.102. If the air-conditioning or refrigeration unit falls under the scope of Article 440, the disconnecting means location requirements of 440.13 or 440.14 would apply.


In electrical engineering, a disconnect or, disconnect switch or isolator switch, is used to ensure that an electrical circuit is completely de-energized for service or maintenance. Such switches are often found in electrical distribution and industrial applications, where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers, transformers, and transmission lines, for maintenance. The disconnect is usually not intended for normal control of the circuit, but only for safety isolation. Disconnect can be operated either manually or automatically (motorized disconnect).

Because of the nature of AC Disconnects, and other Electrical issues, it's best to leave this to the pros at SafeSide Electrical Contractor,

Disconnect for medium voltage
Unlike load break switches and circuit breakers, disconnect lack a mechanism for suppression of electric arc, which occurs when conductors carrying high currents are electrically interrupted. Thus, they are off-load devices, intended to be opened only after current has been interrupted by some other control device. Safety regulations of the utility must prevent any attempt to open the disconnect while it supplies a circuit. Standards in some countries for safety may require either local motor isolators or lockable overloads (which can be padlocked).

Disconnect have provisions for a padlock so that inadvertent operation is not possible (lockout-tagout). In high-voltage or complex systems, these padlocks may be part of a trapped-key interlock system to ensure proper sequence of operation. In some designs, the isolator switch has the additional ability to earth the isolated circuit thereby providing additional safety. Such an arrangement would apply to circuits which inter-connect power distribution systems where both ends of the circuit need to be isolated.

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