Earthing / Grounding
The grounding* of an installation is vital and necessary for the safety of people and property. In addition it plays an active role in EMC.
*also called "earthing"
The ground network consists of all metal parts of a building connected together: beams, conduits, cable trays, metal frames or devices, all parts which must be connected together to guarantee the equipotentiality of the ground network.
Rule per the National Electric Code
Per the National Electrical Code section 392, the applicable section for cable tray, all cable tray systems must be properly BONDED, per section 250.96. To meet this requirement, Cablofil recommends that ULclassified splices are used to join sections and that the cable tray be bonded to building steel or the facility grounding system every 50’-60’. By bonding the tray every 50’-60’, the tray will maintain a low potential to ground which reduces EMI and provides a continuous path for stray currents.
How to create a safe system.
Steel trapeze type hangers clamped securely to building steel usually provide a solid bond. Cablofil standard splices (SWK, EDRN, EZBN, EDT, EZT90, RADT90) are designed to have less than 1 milliohm of resistance between connections and provide bonding between sections. These splices have been tested by UL as part of the cable tray grounding system. Painted Cablofil wire mesh tray requires the outer mask of the conductive surface be removed at each end of the tray prior to installing the (SWK) splice. The (SWK) splice provides continuity between UL Classified painted tray sections. All cable tray needs to be electrically continuous per NEC 250.96. Standard Cablofil splices provide continuity per 250.96. Cutting and removal of cable tray sections still allow continuity per 250.96 and only affects the rare use of cable tray as the EGC. Use of cable tray as an EGC is rare since UL requires all multiconductor cables to contain an integral EGC and single conductor cables are only used in a few industrial applications. If the WMCT (Wire Mesh Cable Tray) is to be used as an EGC, an appropriate size grounding jumper including listed/classified lugs are required across the modified WMCT sections.
Advantages of an equipotential ground network
The equipotential ground network works like a system of conductors evacuating any fault currents and the currents to ground.
This provides a means of:
- Protecting people and property.
- Obtaining a satisfactory EMC performance level.
The installer must first determine the cross-section of the protective conductor. The Cablofil® range includes a wide range of suitable accessories:
||GNDSB Grounding Lug: split bolt grounding lug. Accomondates wire sizes AWG 14 to AWG 4.|
|GNDCL Grounding Lug: tin plated aluminum connector representing an easy, low-cost grounding solution for a grounding conductor. Accomondates wire sizes AWG 6 to AWG 2/0.|
Cablofil® Warning! All cable trays are not the same. The mechanical and electrical characteristics, the tests, certification guide refer to Cablofil® only and do not under any circumstances represent other similar products or imitations.