IEE Regulations Voltage Drop

[Noel]

Hi,

To calculate the voltage drop of a cable from Appendix 4 of the IEE Regulations we use the following formula:

actual voltage drop = factor x load current x length
1000

My question is that i tried to solve some problems regarding the current capacity of cables from electrical installation books. It was said that a 2 kW heater at 230 V is installed 30 m away from the consumer control unit. I am confused about what length i have to take whether the 30 m or 60 m, the latter to take into consideration the length of the neutral conductor also. The book solved the problem with the 30 m length.

 

[Noel]

Can someone help which length do i have to take pls?

 

[Noel]

Can someone help me which length do i have to take?

 

[danzor]

length of the cable run?

 

[Noel]

But the length of run includes the phase & neutral conductors or the phase conductor only.

thanks for reply

 

[Shakey]

its just the length of the cable run, so if its 30m away, then its 30m.

we dont 'add on' the neutral length, because its the voltage AT the appliance that we are concerned about, not the voltage that 'returns'

and the V that hits the appliance on the line conductor, could be 235v, could be 230V, could be 225V - doesnt matter, because on the other side of the 'load' (on the neutral) it will be zero, regardless of what it was to start with

hope that helped

 

[Noel]

Yes, now it is more clear.

Thanks

 

[Noel]

Voltage Drop on dc supply

As it was already said on ac supply the voltage drop on the neutral conductor is not taken into account when calculate the permissible voltage drop, since it is at zero potential in TT system.
What about if the system is dc instead, do we need to take into consideration the resistance of both conductors (+ and -) or take the resistance of the positive conductor only to calculate the voltage drop in cables.