How to terminate SY cable with cable glands

Helpful video reference. We use GSH Electrical's practical demonstration "SY Cable or SY Flex How to Terminate, Make Off Step by Step Practical Demonstration of Connecting" as the video reference here. GSH Electrical is a UK-based training channel for apprentice electricians and learners working towards City and Guilds and EAL qualifications. Their step-by-step demonstrations are particularly clear on the gland and braid handling.

1. When and why SY cable is used

SY cable (also called SY flex or screened armoured flexible cable) consists of copper conductors over an aluminium Mylar foil and a tinned copper braid screen, all wrapped in a grey PVC outer sheath. The braid screen serves two purposes: it provides mechanical protection for the inner conductors against minor abrasion, and it gives electromagnetic compatibility (EMC) screening to reduce interference from variable-speed motor drives.

You will find it used for:

• Surface wiring to workshop machinery: compressors, lathes, pillar drills, extraction units
• Connections to control panels and industrial equipment in garages and outbuildings
• Flexible connections to surface-mounted isolators where the final few hundred millimetres need to flex slightly with vibration

SY cable is not suitable for buried use, outdoor UV exposure, high-temperature environments or wet locations. For those applications, use steel wire armoured (SWA) cable or appropriate heat-resistant flex.

2. Tools and materials

You need a CXT-pattern brass cable gland (also sold as DEG or similar branded names) in the right metric size for your cable diameter, plus a matching PVC shroud and lock nut. For 3-core 1.5mm² SY cable, M20 is usually correct. For 3-core 2.5mm², check the gland manufacturer's selection chart - the cable diameter varies slightly between manufacturers.

You also need a sharp cable knife, a pair of small side cutters, a flat-bladed screwdriver, an adjustable spanner, and a continuity tester or multimeter set to the resistance range.

3. Measure, cut and strip the outer sheath

Cut the cable end square. Using a cable knife, carefully score around the outer sheath at a point approximately 50mm back from the cut end - just deep enough to cut through the sheath without nicking the braid beneath. Bend the cable back and forth at the score mark to split the sheath, then pull the sheath off. You should now be able to see the steel braid.

Do not cut through the braid at this stage. If you accidentally nick individual braid wires, check the gland will still grip them securely before proceeding.

4. Prepare the steel braid

Use the tip of a flat-bladed screwdriver to tease open the braid wires at the cut end. Work your way round the cable gently separating the braid away from the foil and inner cores. Once you have a loose collar of braid, fold it back over the outer sheath so it lies flat against the cable jacket. Some installers use a small hooked pick or the screwdriver to ease the braid wires through the gland's braid gripping ring - the goal is a neat, even cuff of braid that sits at the junction between inner cores and outer sheath.

5. Thread the gland back nut and compression ring

Before you do anything else, thread the gland back nut onto the cable (from the cable tail, not the prepared end) followed by the compression ring. These cannot go on after the gland body is in place. Slide them back along the cable until they are out of the way.

Now slide the gland body over the prepared end of the cable. The inner cores should protrude through the front face of the gland, with the folded braid sitting inside the gland body. Bring the compression ring and back nut up to the gland body and tighten the back nut finger tight first, then a quarter turn with the spanner. This grips the outer sheath and captures the braid between the compression ring and gland body.

6. Terminate the inner conductors

Strip the inner conductor insulation by approximately 8mm to 10mm. The colour coding in SY flex follows the harmonised standard: brown for line (live), blue for neutral, green-yellow for protective earth (PE). Connect these to the equipment's terminal block in the correct positions.

If the equipment has torque specifications printed on the terminals or in the installation manual, use a torque screwdriver. For most domestic machinery without a specified torque, tighten firmly until the conductor is gripped without crushing the insulation.

7. Connect the braid to earth

The braid must be connected to earth. Most CXT glands have an earth lug projecting from the body where you can attach a flying earth lead. Run a green-yellow sleeved conductor from this lug to the equipment earth terminal or the enclosure earth bar. Some glands make the earth connection via the gland body itself provided the enclosure is metallic and earthed - check the manufacturer's instructions.

At the supply end (the fused spur, isolator or consumer unit), the gland body should also be earthed via the same method. Where the gland screws into a metal enclosure with a good metallic connection, the enclosure earth bonding may be sufficient. Where the enclosure is plastic, an explicit flying earth lead from the gland to the earth terminal is needed.

8. Fit the shroud, tighten and test

Slide the PVC shroud over the front of the gland body and lock it in place with the front lock nut. Tighten the lock nut with a spanner. The shroud provides basic mechanical protection and a degree of ingress protection - check the gland's IP rating if the installation is in a damp or dusty environment and choose accordingly.

Before energising, use a continuity tester between the braid or gland body at one end and the earth terminal at the other. The reading should be very low - a few tenths of an ohm at most. A high reading suggests a poor connection at one of the gland earth lugs; re-check and tighten. Once you have a confirmed continuous earth path, the installation can be energised.