Differnet cable sizes in a run

[DJM]

Some of you may remember I asked about a 9.5Kw powerstream which is on 6mm2 cable and 45A fused at CU. I thought this was a bit thin and you all agreed.

So trying to get a quote for running 16mm2 cable to allowfor a more powerful powerstream (the 9.5Kw is broken anyway), and downloaded the Powerstream hand book.

It states for the 10.8kW and 12kW units:

This unit has been designed to accept 10mm2 supply cable. Therefore this is the size of cable that should be used between the isolator switch and the unit, even if you decide to use 16mm2 between the fuse box and isolating switch.

If the cable length (ie approx 15m) indicates 16mm2, what will reducing to 10mm2 between DP and unit do? Should I just stick witht eh 9.5kW unit and put in 10mm2 all through?

As a side issue, the powerstream handbook also suggests that 6mm2 cable is sufficient for the 9.5kW unit if surface run and less than 10m.

 

[EddieCurrent]

Hello,
Changing from the 16mm down to 10mm from your DP isolator to the shower restricts the circuits current carrying capacity. (it would restrict you to a lesser value(a) mcb).

Is the cable going to be clipped direct to a wall, in a thermal wall etc ????


Hope this helps.

 

[DJM]

Eddiecurrent, that's exactly my concern. I can't understand why edring recommend 16mm2 from CU to DP and 10mm2 from DP to load. It seems to negate the use of 16mm2, and I cant see how 10mm2 is valid for the 12kW unit anyway

 

[EddieCurrent]

Hello,


Different methods of installation allow for different current carrying capacities.


If 10mm cable was clipped direct to a wall, you could have a 40m run @ 12kw !!.

 

[Pensdown]

Above is a quick calcualtion based on 10mm T&E @ 12kW

The last two are 6mm T&E @ 9.5kW

So unless there are any other de-rating factors you should be OK.

 

[Lectrician]

Good Old Amtech

 

[Pensdown]

The down side with Amtech is you start to forget how to work it out long hand

 

[DJM]

Thanks Pensdown,

the run is currently just under 10m CU to DP and then about 3m DP to load run in 6mm2 cable. The cable is bunched near the CU, clipped to joist, run through airing cupboard and stud wall to CU and then on to load.

So it looks as it is a bit of a stretch too far for the 6mm2 cable, but should be fine in 10mm2. Would you agree?