Armoured Cable Glanding and Earthing: How to Terminate SWA Cable Without Water Ingress
Most armoured cable failures we investigate are not cable failures at all — they are termination failures. A gland that is over-tightened, an earth tag left loose, or a sheath cut back too far will destroy a perfectly good drum of SWA cable within one rainy season. This is the termination sequence we recommend to contractors.
Why the Armour is the Earth Path
In a typical buried distribution circuit, the armour doubles as the circuit protective conductor. That works because steel armour has a low resistance and a large surface area for heat dissipation during an earth fault. It only works, however, if the armour is mechanically and electrically continuous from gland to gland — which is a termination question, not a cable question.
Tools and Components
- Correct-size brass or nickel-plated brass gland (CW, BW or A2 type depending on cable and enclosure).
- Earth tag, locknut, shroud and a brass or tinned copper earth tail.
- Armour cutting tool or hacksaw with depth stop, cable knife, and a bonding conductor sized to the circuit.
- Insulation resistance tester and a low-resistance ohmmeter for continuity.
Termination Sequence, Step by Step
- Measure and mark the sheath cut-back against the gland body length plus enclosure wall thickness.
- Cut the oversheath carefully along the axis only where the gland will clamp — do not score the armour wires.
- Expose the armour to the depth required by the gland, keeping the bedding intact under the armour.
- Fit the gland body and earth tag, then tighten the armour clamping ring so the wires are captured, not crushed through.
- Bed the cone into the sheath to create the seal, then fit the shroud.
- Connect the earth tail from the earth tag to the enclosure earth bar with a crimped lug — not a twisted wire.
- Test: insulation resistance core-to-core and core-to-armour, then earth continuity from gland to gland below 0.1 Ω.
Six Mistakes That Cause Water Ingress
| Mistake | Consequence |
|---|---|
| Sheath scored while stripping | Radial crack propagates, water reaches armour |
| Armour wires cut unevenly | Gland seal incomplete, low pull-out strength |
| Gland over-tightened | Bedding crushed, insulation pinched, reduced dielectric strength |
| Earth tag omitted or loose | Armour not earthed, fault current finds another path |
| Cable not supported near gland | Weight loads the termination, seal opens over time |
| Indoor gland used outdoors | No IP seal, water tracks into the enclosure |
Earthing Both Ends or One End?
For LV circuits, earth the armour at both ends. For single-core cables in parallel, the arrangement needs care because circulating currents can flow in the armour; in that case use aluminium wire armour or a single-point bonding scheme designed by the electrical engineer. Never leave an armour floating at a cable joint — a joint kit that does not restore armour continuity is a latent fault.
Testing After Jointing
- Insulation resistance: 1 kV tester for LV circuits, values typically above 100 MΩ.
- Voltage test: 3.5 kV / 5 min for 0.6/1 kV cable, per IEC 60502-1.
- Earth continuity: from the far gland to the switchboard earth bar, below 0.1 Ω.
- Sheath and gland inspection: shroud seated, no exposed armour, enclosure IP rating restored.
For cable construction and armour selection, see the armoured electrical cable guide and the armoured cable selection guide.
