Technical Data TD00801005E Effective June 2011 Combination short-circuit current ratings for non-fusible safety switches Recent system studies have shown that many non- fusible safety switches used in industrial facilities are being applied in systems where the available fault current exceeds the product listing. A study for the system shown in the one-line diagram, Figure 1, proved that the available short-circuit current at the safety switch applied as a local motor disconnect was 13.5 kA. Eaton has completed testing as defined by the UL 98 standard for heavy-duty non-fusible safety switches to achieve a higher level of series combination ratings with upstream Eaton molded- case circuit breakers and various fuse types. Utility 12,470V SC 3P 100 MVA Transformer Fused Switch Safety First: protecting people Overload Fuse Links, 15.5 kV and equipment 125A P Power Transformer The recent changes in Electrical Workplace Safety 2500 kVA 12,470/ S Standard NFPAT 70E recommend that industrial 480V 5.75% Z users and building owners conduct an arc-flash Bus Duct0001 hazard analysis for their facilities. This analysis LV Switchgear 1 3200, 5 ft includes a short-circuit, coordination and arc-flash Main Switchgear system study conducted by a professional engi- Eaton Magnum DS, Main neer, which identifies the available arc-flash energy DT 520 Switchgear 3000A/3000A measured in calories per centimeter-squared 480V 2 36.66 kA (cal/cm ) for electrical equipment throughout MCC1 FDR MCC2 FDR MCC3 FDR the facility. Then, a special label is affixed to the Magnum DS, Magnum DS, Magnum DS, equipment warning persons working on it while DT 520 DT 520 DT 520 energized of both the arc-flash energy and the 800A/800A 800A/800A 800A/800A personal protective equipment needed to ensure that the worker is adequately protected. Cable0001 2 500, 35 ft The ULT 98 Standard (Enclosed and Deadfront Switches) allows non-fusible switches to have LV Motor Control Center a maximum short-circuit interrupting rating of MCC1 10 kA. This is because as a stand-alone device 480V 32.91 kA without integral overcurrent protection, the system designer may not know the upstream overcurrent MTR FDR MTR FDR MTR FDR HMCP HMCP HMCP protection. UL permits higher series connected fault current ratings if specific products are tested MTR O/L MTR O/L MTR O/L together. UL Listed combination ratings must be Class 20 Class 20 Class 20 printed on the safety switch pub on the door, and Cable0002 must specify which upstream devices may be used 1 4, 50 ft to protect at higher fault current levels. Additionally, UL does not permit series combination ratings with motor circuit protectors. Motor Disconnect 480V 13.5 kA Motor 50 hp Figure 1. Technical Data TD00801005E Combination short-circuit current Effective June 2011 ratings for non-fusible safety switches Product enhancement Information and application In Table 1, Eaton non-fusible safety switches, within the noted The circuit breaker or fuse rating is not to exceed the ampere ampere ratings, now carry series combination short-circuit ratings as rating of the non-fusible switch. When used on systems with greater shown when combined with the identified MCCB or fuse type. With than 10 kA short-circuit rating available, the UL Listed short-circuit this listed rating, the safety switch shown in the one-line diagram, rating of the non-fusible switch is based upon the switch being used Figure 1, can be correctly applied when the motor feeder Eaton in combination with fuses or molded-case circuit breakers identified HMCP circuit breaker is replaced with an Eaton molded-case in Table 1. circuit breaker properly sized for the motor hp rating. This is a significant enhancement to the products performance rating. To achieve these ratings, the switches have been tested in combination with all of the overcurrent devices shown. Furthermore, the applicable combination ratings are marked on the inside of the switch door, ensuring inspector approval. Table 1. Non-Fusible Safety Switches b Upstream Device Eaton Non-Fusible Safety Maximum System Maximum Short- a Switch Ampere Rating Voltage AC Circuit Rating Fuse Class Breaker Frame 30 and 60 600 10,000 H, K Any circuit breaker 14,000 FDB 18,000 FD, EGE 25,000 FDC, HFD, HFDE, EGH 200,000 R, T, J, L 100 480 10,000 H, K Any circuit breaker 35,000 EGH, EGS 200,000 R, T, J, L 600 10,000 H, K Any circuit breaker 14,000 FDB 18,000 FD, EGE 25,000 FDC, HFD, HFDE, EGH c 200,000 R, T, J, L 200 480 10,000 H, K Any circuit breaker 65,000 HFD, HFDE, HJD, JGH 200,000 R, T, J, L 600 10,000 H, K Any circuit breaker 14,000 FDB 18,000 FD, JD, JGE 25,000 FDC, HFD, HFDE, HJD, JGH 200,000 R, T, J, L a For use on NEMAT 1, 3R, 12/3R, and 4X switches. b Fuse or circuit breaker rating is not to exceed switch rating. c NEMA 12, 4/4X only. NEMA 1, 3R are 100 kAIC at 600 Vac. 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