The communication wire, often a 14-gauge, 4-conductor stranded cable, is what allows the indoor unit and outdoor condenser to "talk" to one another. This wire sends signals for the fan speed, compressor frequency, and error codes while also providing power to the indoor air handler. Using the wrong type of wire, such as solid core instead of stranded, can lead to interference and system malfunctions in Cooper&Hunter units. It is essential that this wire is protected by a conduit where it is exposed to the elements to prevent weather damage. Most of our one zone wall mount kits include a standard length of this wire to simplify your project. You can find additional wiring and electrical parts on our site to finish any custom installation.