Voltage Drop

[irelandnewyork]

Hi Guys,
I have an installation where i am running in a new sub panel that is 120 feet away from the main panel. It will be 120/208 single phase, all the loads will be 120v loads which include lights and general outlet circuits the total non cont load will be about 20/30 amps per phase.
With this basic info, single phase 120/208, thhn cu, 1-3 conductors in a conduit, ambient temp 26-30.
I am coming up with #6 at 30 amps i dont think this sounds right, basically i want to know what size of cable would be good to supply the sub panel given it would pull 20/30 amps per phase
Thanks in advance for the replies

 

[Volta]

Looks like #8 would keep you under 3% drop, you could go to about 37 amps.

But of course, it is so easy to want to add a little load in the future, may not be your problem, and maybe no one wants to pay for it, but at #6 you could get 55 amps still under 3% drop.

 

[cdcengineer]

I got one for you.. I didn't think this post warranted another thread..

We have a run that's about 800'. 225A/3P feeder at 208V.

The feeder is from a generator to a distribution panel at 535' away and than we continue one with the 2nd run at 265'.

The most significant load is a 13.6HP elevator. The mfg. recommends sizing feeder at 97 Amps which I assume is full load running. The other loads are some ventilation fans, EM lighting and other EM loads (dampers, etc.).

I calculate the connected load for the combined first and second loads at 190A, the 2nd run drops 15A - so we continue on with 175A.

I am proposing 2 sets of 600AL which is huge in the eyes of the contractor.

The elevator is used as a means of egress (re: 4 or more stories above grade, IBC..)

I am taking PF at 95% which I think is fair. The reality is that this may never draw the 190A, but I don't know if I'm being too conservative. Life safety makes me err to the conservative side.

Anyone have any input?

Thx