Voltage drop

[jmlelectric1@yahoo.com]

What size conductors do i use for a 120/208 400 amp service that is going to be 400 ft from electrical room.

 

[dkarst]

What size conductors do i use for a 120/208 400 amp service that is going to be 400 ft from electrical room.

I'm certain people will hop in with some useful feedback if you state what you think it should be and show your reasoning. For example, 500 kcmil @ 400' gives a drop of x volts which is y%.

 

[Dennis Alwon]

You need to know the load. If you want to know the size wire needed for 400 amp load at 400 feet then a 600Kcm copper wire is needed.

You can use this VD calculator

 

[jmlelectric1@yahoo.com]

60 devices drawing 17 at the most each. could all be plugged in at same time but highly unlikely

 

[Dennis Alwon]

60 devices drawing 17 at the most each. could all be plugged in at same time but highly unlikely

17 what? 17 amps or 17 watts?

 

[hurk27]

17 what? 17 amps or 17 watts?

sure hope watts, because if it is amps, that would be 510 amps per leg:roll:

 

[hurk27]

sounds like winter hitching post set up for truck block heaters, and if thats 17 amps @ 240 volts your going to need a bigger service?

 

[hurk27]

Think I found our answer to our question:

calculation 3 phase power

 

[bob]

Assume load is watts
17 w x 60 = 1020 watts or 3 amps. Must not be watts.

Assume load is amps at 208 volts

17 amps x 60 devices x 208 x 1.73 = 367 kw

amps = 367 kw/0.208 x 1.73 = 1020 amps per phase

400 amps panel might be a tad too small.

4 - 500 kcm per phase may work.

 

[hurk27]

I found what the load is going to be in the above link I posted above:

vending machines @ 120 volts

so he doesn't even know if he has 120/208 volts yet. and thinks he has a 100 amp 480 volt supply up in the ceiling.

even then 60/3x17= 340 amps per phase or 122.4kva

would be fine on a 120/208 400 amp service

 

[jmlelectric1@yahoo.com]

thanks

thanks

thanks for all the help. Im sure ill be back soon with more questions