How NOT to Terminate 3 Core SWA Cable


I had problems with a low resistance fault on a ring final circuit during testing last week. After breaking the ring into sections I identified the defective section. I had to lift the floorboards in a bedroom to check for any cable defects or jointed connections. I was surprised to find the following junction box connection. It was connected to a supply to the detached garage outside.

How NOT to Terminate SWA Cable

The picture above shows SWA cable supplying a detached garage. The cable was connected into domestic Ring Final Circuit [RFC] under upstairs bedroom floor. SWA outer armour was not bonded at either end of cable run. PME/TNCS earthing system, so no adequate means of earthing in the garage. The SWA circuit cable was disconnected for safety reasons.

The picture below shows what should be done. A correct gland coupler has been used to connect outer armour to the accesory. This provides mechanical protection of the inner cores and a means of earthing of the outer SWA strands.

SWA Cable and Gland Coupler

I now use an adjustable pipe cutter to prepare SWA cable for connection to gland couplings.

Adjustable pipe cutter can be used to prepare SWA cable for termination into a gland coupler.

Two turns to cut outer PVC, then five to ten turns to cut individual SWA strands. This process is much quicker and cleaner than using a hacksaw.

The picture below shows the quality of preparation using an adjustable pipe cutter.

 

Hand cut SWA using a hacksaw and/or side cutters can be subject to failure due to uneven SWA strand lengths.

SWA cable cut using a hacksaw. Note uneven strand lengths. This makes connection to gland difficult with possible failure of coupling and bonding of SWA strands.

A little extra care and attention in the preparation can make for a much improved and long lasting installation.

Please let me know if you have any tips to improve the standard of electrical installations.

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