Ambient temps and voltage drop.

[sheeni]

Hi guys,

Can somebody please help me out with the correct voltage drop on a 120mm 5core double insulated cable non armoured, on a 208v system , lay surface for a run of 10m. It has an ambient temp of 90 degrees / no thermal insulation and is being protected by 250A 3pole 60947-2 main sw.
I have worked out that the overcurrent protective device is oversized and requires reducing, but been a while since doing voltage drop calculations and nt 100% sure if i've got the correct voltage drop and want to confirm this. Could you please put down your figures ie Ca = 90 / Cg =0.6 etc so i can once again check mine.

Cheers

 

[malcolmsanford]

What regulations are you working to BS 7671 or the NEC ?

208 is 3 phase North America and the chances are you will be using AWG and their calculation for VD is done in imperial.

 

[sheeni]

Its NEC installation but was working out to BS 7671, the cable is actually a 4/0 Awg but have converted into mm which equates to 120mm on the conversion chart given.

 

[malcolmsanford]

You need the AWG values of the cable I'm afraid, you can't work out a VD on that size of cable like your doing.

Also you will need to confirm what kind of load it is ie resistive, inductive or mixed.

 

[sheeni]

Brilliant, i will request the required information. Thanks for your help