Acceptable practice

[dave12]

Hi,

I have a 10mm (3 core) cable that will be pulled backfrom it's existing termination and re terminated into a JB. Within the JB will obviously be 10mm Terminals.

The loading of the cable is such that a 2.5mm cable would have been sufficient, however due to the length of run 10mm has been used. (still a bit excesive). So my question is, would it be acceptable to use2.5mm cable from the JB to the new load. The distance is only short and so I have no issues with Volts drop or load. My main concern is terminating a 2.5mm cable in a 10mm Terminal.

Could anyone advise if this would be ok or recommend an alternative solution.

Many thanks in advance. Just as a side note, this is not a domestic installation but an industrial one.

Cheers

Dave

 

[sparkticus]

1) It would not be good practice.

2) The fuse/MCB that protects the 10mm cable would need to be rated for the 2.5mm cable.

3) In the future someone may change the fuse for a higher rating based upon seeing just the 10mm cable size!

4) Depending upon the length of the 2.5mm you may still have voltage drop problems and possible problems obtaining an acceptable Zs. Though lowering the rating of the protective device will increase the maximum permitted Zs.

5) Wiska junction boxes have connectors that would easily allow 10mm and 2.5mm CSA in the same receptacle. Or you can use the individual connectors that are secured with a grub-screw and a shroud placed on top.
http://www.tlc-direct.co.uk/Products/PRCON4.html
Double the 2.5mm over or put an uninsulated crimp on the 2.5mm.

 

[dave12]

Cheers Sparkticus,

The MCB that the cable will feed is 16A so 2.5mm should be ok. The Cable length will be approximately 3m (max). And the internal wiring of the panel which the cable feeds (from the other side of the MCB) is 2.5mm.

The Terminals I intend to use are SAK10 type terminals, that are capable of securing 2.5mm cable.

Thanks again for your advise.

 

[sparkticus]

That's a short length of 2.5mm and it all sounds quite safe (assuming the T&E is appropriate for the environmental factors) but I would be tempted to place a label in the vicinity of the CU (or on the CU) warning that the fuse rating must not be increased.

Is this a domestic/commercial job using a type B, 16amp MCB where your max Zs will be 2.87?

I am assuming you are not using a type D where the max Zs would be 0.72?