Transit walkway lighting design

[lmichael310]

Hi I am a new user here and I am trying to increase my design experience. I am working on a design to light a walkway. There are 19 luminaires to be installed in series along a walkway staggered by 100 ft and the luminare rating is 150 W. I have a 480 V 1P 3W from a substation and I want to see if my design approach is correct. First I found the VA for each luminare to be 265 voltamps, giving me a current of .55A at the last luminare and a current of 10.49 at the first luminare. The total load I caluclated as 10.49*1.25=13.11. Which gave my a 15 amps for the OCD at the panel. I then sized the wire to have a VD less than 3% and I get a #6 wire. One question I did have is how do i select the ground wire size, its based on OCD correct?

Thanks in advance for you help

 

[Dennis Alwon]

The equipment grounding conductor must be upsized proportionately to the ungrounded conductors. Art. 250.122(B) First use T. 250.122 then art. 250.122 (B). Basically if you start with a #12 for your ungrounded and egc then increase the ungrounded conductor to #6 you must increase the egc to #6

Welcome to the forum.

 

[lmichael310]

Ok, thank you. I read article 250.122 and that makes sense now. Also I want to confirm, did I size the CB correctly based on the numbers I provided?

 

[augie47]

I agree with Dennis and add that if your actual load is 13.11 amps you also need to take into account that this is a "continuous load" (3 hours or more) and your 15 amp OCP should be increased to a 20 amp, IMO.
and
as Dennis stated, Welcome to the Forum.