Connecting different sized cables

[faraway73]

Just wondering how everyone would connect a 120mm2 2C+E cable (Cable 1) to a 16mm2 cable 2C+E(Cable 2). Cable 1 is from the switchroom (upstream CB is 32A) to a remote room (very long run I have been told) and is 120mm2 for volt drop. Both cables are copper. Once Cable 1 enters the remote room, it needs to connect to Cable 2 to power a cabinet, with loads of 16A or less. I was thinking of a junction box with an isolator or something along those lines? How does everyone usually connect cables that are so different in size?

 

[ScottyUK]

Terminal box with stud or busbar feedthrough terminals? Resin joint with bolted lugs?

 

[profbuxton]

Isn't it a requirement that if changing cable sizes it has to be done via some downstream protective device(fuse, breaker) is downstream cable is smaller CSA than upstream.

 

[ScottyUK]

that depends upon whether the upstream protective device is sized to protect the smaller cross section cable, which is entirely possible if the larger cable is only oversized for volt-drop rather than for loading. In this case I would say that a 32A breaker protects both cables from a thermal perspective, but it is indeterminate from the information provided whether or not that breaker is adequate to meet disconnect times for short-circuit and earth fault.

 

[madmantrapper]

Or it might fall under a tap rule.