Air Conditioner House Wiring

Window Units

• Free-standing air conditioners -- typically installed in windows -- are usually supplied with a flexible cord that plugs into an outlet. The cord should have been designed by the manufacturer to be the maximum safe length. Because the compressor in an air-conditioning unit uses a great deal of power and spikes to an even greater demand on start up, extension cords are not advised. If a pre-existing outlet is not located within the reach of the integral cord, or if reaching the outlet means running the cord across a dangerous space such as an area subject to heavy foot traffic, a new outlet should be installed. The new outlet should not share a circuit with another high-demand appliance, such as a water heater.

Rooftop Units

• Many manufactured homes and mobile homes situate an air conditioner on the roof; rooftop units must be hardwired. “Hardwired” means the machine is powered through a junction box inside where permanent connections are made, as opposed to being plugged into an outlet. Wiring to these appliances should be routed through a wall to protect it from accidental damage or sheathed in an approved conduit if mounted externally.

  If you're replacing an pre-existing rooftop air conditioner due to wear and tear or because of a mechanical or electrical problem, purchase new wiring that extends back to the fuse or circuit board at the same time. An entirely new installation will be safer and is less likely to experience service problems. Replacing the wiring at the same time as the air conditioner is likely to be more cost-effective than doing the two jobs separately.

Central Units

• Central air conditioners located outside the building must also be hardwired to a dedicated supply; this minimizes voltage loss and removes the possibility of supply interruption from corroded plug terminals or outlet receivers. Some larger residences may have central air conditioners that use 220-volt power -- the voltage used by typical clothes dryers and stoves -- rather than 110 volts. A new 220-volt power supply should be run from the fuse or circuit breaker board to the location of the air conditioner; pre-existing circuits should not be shared. Consult your local code enforcement office before beginning the project to learn if there are any regulations the installation must meet.

Code

• The National Electric Code covers all aspects of household wiring in great detail. While the code is not a mandatory set of regulations, it is used by most municipal authorities as a reference when they establish their own. Your local code enforcement office and library should have a copy of the code for public inspection.