Patent ID: 8598886

Claim:
Apparatus for detecting faults in the delivery of electrical power to electrical loads, comprising: a plurality of load electrical connections arranged to deliver electrical power from an electrical power source to each of a plurality of electrical loads; a plurality of electrical switches each connected to an associated one of the load connections; a diagnostic device operable to detect a short circuit fault in the apparatus, the diagnostic device being operable to apply a diagnostic procedure to detect a short circuit connection between at least two of the load electrical connections, wherein the diagnostic device applies a test electrical signal to one of the load electrical connections in an operational mode of the apparatus when an electrically controlled switch connected to the load electrical connection is in an off state; a control logic unit operable to apply to at least some of the electrical switches in turn a test control signal causing operation of the switch; and a detector connected to the load electrical connections and operable to detect, whilst the test control signal is applied to each of the switches in turn, whether an electrical output is produced at a load electrical connection indicating a short circuit connection at the load electrical connection; wherein the control logic unit is operable when the test control signal is applied to a first one of the switches connected to a first one of the load electrical connections to deliver a control signal which puts other switches in an off state, and the detector is operable to detect, when the first switch is operated, and the control signal has been applied to the other switches to put the other switches in an off state, whether in response an electrical output indicating a short circuit connection to the first load electrical connection is produced on any of the other load electrical connections connected to the other switches in an off state.