Components of a distribution system 343 Table 13.3 Ampacity of spider boxes Continuous Cable Slots per Bar 4 6 8 Amps per Cable 300 280 270 Amps per Bar 600 840 1080 Amps per Cable 325 325 325 Amps per Bar 650 975 1300 Intermittent Minutes On 20 20 20 Minutes Off 6 10 14 Note: The amperage data in Table 13.3 apply to spider boxes that are not listed if they have the same number of lugs per bar. This table gives Mole-Richardson's recommended maximum loading.