An apparatus for detecting a pipe length in an air conditioning system includes a detector to detect a signal traveled through a pipe and a first impedance coupler that couples to one end of the pipe, where the detector detects the signal traveled through the pipe at the first impedance coupler. A processor determines a pipe length based on the detected signal and a signal generator generates the signal to be sent through the pipe. A second impedance coupler couples to another end of the pipe, where the signal generator sends the signal to the pipe through the second impedance coupler.