Full scale fire experiments on electronic cabinets II

Three full-scale fire experiments on electronic cabinets have been carried out. In the experiments, one cabinet, the fire cabinet, was fitted with relays, connectors, wiring, cables and circuit boards. A mock-up cabinet made of thin steel sheets was attached to the fire cabinet in order to study the response of an adjoining cabinet to the fire. Another cabinet was placed at a distance of 1 m opposite the fire cabinet to represent a neighbouring row of cabinets. The fire cabinet was ignited with a small propane burner either at the bottom of the cabinet beneath a vertical cable bundle or beneath a wiring bundle. The rate of heat release by means of oxygen consumption calorimetry, mass change, CO2, CO and smoke production rate, and gas and wall temperatures in all three cabinets were measured as a function of time. The key role of the ventilation conditions in the cabinet was clearly shown by determining the rate of heat release. The ignition power and energy sufficient for sustained burning leading to flashover in the cabinet was determined. The ignition power and energy levels seem to be fairly near the ignition/no ignition limit of the cabinet. The fire growth rate after ignition was estimated to be slow.