In some embodiments, a remote device can periodically send an enable command, which can be a heartbeat indication, to some or all the modules in an array instructing them to remain enabled (or become enabled) for a period of time. Should a module not timely receive the heartbeat indication, its controller 130 can determine to disable the PV module and then disable the PV module (e.g., by enabling the parallel current path). In one embodiment, the heartbeat transmitter can be powered by the AC grid, by the inverter's output, or by a separate power source. If the heartbeat transmitter is powered by the inverter's output and the inverter correctly detects disconnection of the AC power grid, then disconnecting the AC power grid at a location remote from the inverter would cause the inverter to shut down, causing the heartbeat transmitter to lose power. The controller or controllers corresponding to the PV modules would fail to receive the heartbeat within the expected period of time to receive the heartbeat and then disable the modules. By doing so, the inverter and some or all modules feeding it can be disabled and stop producing a hazardous voltage without requiring any work to be done near the modules (i.e., service and/or emergency personnel do not have to approach the array to put it into a safe state).