EDP-3 - Cooper Bussmann

Protecting System ComponentsH. HVAC EquipmentHeating and cooling equipment must meet short-circuittest requirements in U.L. Standard 1995 and CSA-C22.2No. 236-M90. Short-circuit tests are conducted at variouslevels, up to a maximum of only 5000 amperes, dependingon the rated current and voltage of the equipment.Where available fault currents exceed the values givenin Table 55.1 of U.L. 1995 (Table 8 at right) it is necessaryto specify a current limiting device to reduce the availablecurrent down to within the withstand capabilities of theequipment.Class J and Class RK1 dual-element current-limitingfuses will offer the best component short-circuit protectionand current-limiting characteristics for this type ofequipment.Table 8. Short-Circuit Test Currents*Product Ratings, ASingle-PhaseCircuit Capacity,110-120V 200-208V 220-240V 254-277V A9.8 or less 5.4 or less 4.9 or less – 2009.9-16.0 5.5-8.8 5.0-8.0 6.65 or less 100016.1-34.0 8.9-18.6 8.1-17.0 – 200034.1-80.0 18.7-44.0 17.1-40.0 – 3500Over 80.0 Over 44.0 Over 40.0 Over 6.65 50003-PhaseCircuit Capacity,200-208V 220-240V 440-480V 550-600V A2.12 or less 2.0 or less – – 2002.13-3.7 2.1-3.5 1.8 or less 1.4 or less 10003.8-9.5 3.6-9.0 – – 20009.6-23.3 9.1-22.0 – – 3500Over 23.3 Over 22.0 Over 1.8 Over 1.4 5000* Table 55.1 of U.L. Standard 1995.24