Earthing Nuts benefits at-a-Glance
- Allows SWA and MI cable (in fact any cable that requires a metal cable gland) to be easily used where plastic enclosures are beneficial.
- Can be used with a standard gland where ordinarily an Integral Earth gland would be necessary.
- Not limited to use with plastic enclosures, has advantages when used with metal enclosures.
- Suitable for use where high protective conductor fault current exists.
- Enables earth connection to be made inside the enclosure, away from the corrosive or hazardous atmosphere outside. Connections are therefore protected from mechanical damage.
- Creates a neater appearance than an Integral Earth gland.
- May be used with MI cable, no need for earth tail pots.
- Retro-fittable, to upgrade to high integrity earth connection where earth tail pot has not been used.
- Enables braid of flexible (SY) cable to be easily bonded to earth when used with ‘top hat’ style gland.
- Provides local earthing connection to gland plate/enclosure wall for EMI / RFI screening.
- Vibration resistant.
Previous correct methods
- Earth tail soldered to inside of gland. Time consuming. Only suitable for smaller glands due to mass of metal to be connected and heat required by larger glands and cables, and room available to connect.
- Banjo washer brazed to gland body. Time consuming. Earth cables and connections outside enclosure susceptible to damage and corrosion.
- Sandwiching banjo in between two lock nuts. Extra lock nut required, fiddly to tighten, unsuitable for thicker gland plates.
- Terminating cable through plastic flex gland and connecting all armour wires to internal terminal. Wires stiff to bend, lots of room required to take large connector. Only suitable for small cables.
Previous incorrect methods
- Conventional use of banjo and nut and bolt through plastic enclosure. Joints become loose when plastic becomes warm. Will cause high resistance joints. Should fault to earth occur, joint could explode.
- BS 951 Earth clamp fitted around bared armouring. Against BS 951, allows moisture into cable when used in damp conditions. Under earth fault conditions armour wires migrate into cable, loosening clamp, increasing resistance and heat, resulting in melted cable and possibility of explosion.
- Connection of less than total armour wires to earth terminal within enclosure. Depending on number of wires used, reduced CSA of protective conductor, possibility of connecting one set of wires one end and different set of wires at other end, leaving fault current to pass between wires along cable. Could cause loss of earth connection or cable to explode.
- Gland fitted to metal enclosure without earth tag and earth connection. Under serious fault currents gland can punch a hole in enclosure wall with severe arcing.