An electrical installation with circuit integrity of an electric through line under fire impact. Branch off devices are connected to the through line, and branch lines are connected to the branch off devices. The branch off devices include a thermally triggering disconnect device for providing circuit integrity of the through line under fire impact. The disconnect device is configured to disconnect an electrical connection between the branch line and the through line self-acting when an ambient temperature increases to a predetermined value that is typical for a fire. An installation kit and a branch off device for such an electrical installation.