Voltage Drop

[SourceElectric]

I was wondering about Voltage Drop. What I’ve always done but I wanted to see what others have done as well. On jobs where I’ve had to run a really big wire because I am going a pretty far distance. Let’s just say 400 or 500 feet. I can’t land that on a lot of the lugs in the panels on each side, so I normally just Polaris block down to a smaller size wire. I usually do this on both sides and I probably limit that piece of wire to maybe 5 to 8 feet long. I’ve never had a problem With Voltage Drop by doing this, but have others done this?

Also, the one I’m doing now is a three phase service but the same thing applies that because of the distance it’s requiring me to run three sets of parallel. I wanted to know if on each side, I could connect those three parallel runs to a single wire with the polaris blocks, granted that that one wire is big enough capacity to handle the load (amps) but would still allow it to function with no Voltage Drop or within the .03 percent allowed? Thanks for anyone’s help.

 

[infinity]

wanted to know if on each side, I could connect those three parallel runs to a single wire with the polaris blocks, granted that that one wire is big enough capacity to handle the load (amps) but would still allow it to function with no Voltage Drop or within the .03 percent allowed?

Yes you can run parallel sets and then pigtail one conductor to the terminals on both ends. The recommended VD is 3% not .03. Of course neither are code required.

 

[wwhitney]

I’ve never had a problem With Voltage Drop by doing this, but have others done this?

FYI, say your run is 400 feet, and you have to use "normal size" wire for the last 4 feet at each end, and for the rest of the run you double the wire area (go up 3 AWG sizes, or from say 250 kcmil to 500 kcmil) to reduce voltage drop. So on the upsized portion, the resistance per foot is halved.

If you had been able to upsize the wire for the full 400 feet, the result would have been halving the voltage drop, a factor of 50%. You can think of that as counting the length that is upsize at just half of the actual length, so 50% = 200/400. I.e. the voltage drop would be the same as if the circuit length were just 200 feet, and you didn't upsize the wire at all.

So with the 8 feet of "normal" size and the 392 feet of upsized wire, the effect on voltage drop would be a factor of (8+392/2)/400 = 51%. Very close to the 50% if you had been able to upsize the full 400 feet.

Cheers, Wayne

 

[gene6]

neither are code required.

Depends what you mean by code, voltage drop is in the International Energy Conservation Code (IECC), the same code that requires occupancy sensors and such, not the National Electrical Code. I would recommend checking with your local 'AHJ' what version of the energy code is in effect (adopted), but most versions of the IECC mandate 5% total, and you can meet that any way you want to.
If a contract says I need to 'meet all applicable codes' then I'd check the IECC as there is other stuff in there including requirements for motors and transformers.