# cable size

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• #10481
Participant

dear all,

i have 20 no,s 400 watt,s helogen light,s. these lights are 50 feet far from the panel. can anybody provide me the exact formula to get exact cable size for it. if anybody have any formula or website or any information about this then please give me. thats my mail address.

thank,s.

#12080
erickench
Participant

Well first you have to determine the current. What's the voltage? Once you determine the current you could use NEC Table 310.16 to determine the ampacity. Use the 75' column.

Power/Voltage = Current

#12128
Spir Georges GHALI
Participant

dear all,

i have 20 no,s 400 watt,s helogen light,s. these lights are 50 feet far from the panel. can anybody provide me the exact formula to get exact cable size for it. if anybody have any formula or website or any information about this then please give me. thats my mail address.

thank,s.

Dear Ikram ;

First, you should know the value of the voltage, then by the total power of lifgts and the voltage's value you can calculate the current of this loas that we call ” Ib “.

Then, you should know the type of installtion's methode, the ambiant temperature, by which you will calculate the total factor coorection ” k “, then calculate Iz = Ib / k, so, by this value and from the tables of ” IEC 60364-5-52 ” you can do your choice of the section of cable, but it's not the end, becuase you should calculate the total value of the ” drop voltage ” from the source to this load, where the IEC defines that the maximum value of the total drop voltage for luminars is ” 3-5% “, so, if with the choiced cable we have more, we should over-domensionned the section of the cable.

Regards.

#12204