Q & A of the Day – What’s the correct way to terminate large CSA conductors into small terminal accessories?

 

Question: Can you advise on the correct method for terminating large CSA conductors into small terminal accessories??

 

As an example, with the 3% volt drop for lighting circuits, some of the cable lengths that we use on agricultural buildings are long - hence the conductor CSA increases, allowing for the volt drop. We then find that the cable CSA is too large to enable a good connection to the accessory (maybe a waterproof socket or light switch), which are only designed for smaller CSA cable connections. 

 

Which is the recommended method of connecting under such circumstances?

 

Answer: BS 767: 2008 requires every connection between conductors and equipment to provide durable continuity and adequate mechanical strength.

 

Where the conductor size is larger than equipment terminals, to ensure a good connection will obviously require a reduction of the conductor size to a size that allows you to make a good connection. You will therefore need to terminate the larger conductors into a suitable accessory or enclosure which will facilitate the reduction.

 

Regulation 559.6.1.1 provides a list of the connections that might be used for wiring systems to facilitate connection to a luminaire and mentions - for instance - the use of a suitable socket-outlet, a luminaire support coupler to BS 6972 or BS 7001, a plug in lighting distribution unit to BS 5733, or a connection unit to BS 1363-4 (fused connection unit) among others.

 

The normal method I often encounter is for luminaires to be connected using a plug and flex to connect to the fixed wiring through a lighting connection box - there are many types on the market.