Receptacle wiring with huge conductor runs!

So I have a site lighting project in which two 277/480V panels feed light fixtures from a centralized location. The light fixture scope of work ends about 2000ft laterally in both directions. There are also two 120/208V receptacle panels. We were instructed to add a receptacle at each fourth light pole for Christmas lights and other miscellaneous connections. The park does NOT want any above ground structures (panels, pedestals, etc), and I would really hate to add underground panels because we would have to supply precast vaults (Structure coordination, sump pumps, ventilation yadayada ya).

Now for the receptacles, assuming I do this with the longest run at 2000 feet and I load 16A (80%). My voltage drop calc shows that I need at least #3/0 wire to compensate!!.........How can I do this without adding other panels?.......I have handholes in the pavement every 300 feet...can I provide terminal blocks in the handholes to step down the wire size from #3/0 to say #12 or 10 when im closer to each receptacle???..........please help!!!
 

GoldDigger

Moderator
Staff member
Is there space at/in the light poles to install step-down transformers?
When you double the voltage you cut the percentage voltage drop by a factor of 4 for the same wire size and length.
I think you can safely assume that only 120 and not 208 will be used for lighting. You can balance the load across all three phases by rotating the phase at successive poles.

Tapatalk...
 
Last edited:

Smart $

Esteemed Member
Location
Ohio
You didn't say how many poles (or receptacles)...???

For the receptacles you should seriously consider running 480V feeder circuit and feeder-tapped transformers. Running 3/0 copper for 120V circuits to 2,000 ft, you're looking what... $$$ into five digits for each run.

While I haven't made any definitive calc's, running a 480V feeder, you can probably get by with a #10... so less than $1k per 2,000 ft circuit?

Other cost consideration off the top of my head... say, 2kVA 480-120V xfmr powering each rcpt circuit: $300. Add secondary fusing, cost of the local 120V wiring (size dependent on xfmer-rcpt distance, but you could stick within #10 constraints and use same wire for entire rcpts run), a couple ground rods, GEC's, clamps, and vaults for each xfmr, etc. Definitely more parts and considerations, but say what.... $$$ less than one-third the cost of running 3/0...
 
A little more detail: The lights are 277V.........there are a roughly total of 150 poles throughout the park running parallel with the walk paths........so there will be multiple 120V circuits
 

GoldDigger

Moderator
Staff member
One more critical detail: what will be the design load for each receptacle?
Clearly 2000 watts per receptacle pole will be a very different design from 200 watts. If the intended lights will be LED, the actual load could be even lower.

With 40 of the 150 poles having receptacles, you might have as few as 4 circuits.


Tapatalk...
 
Last edited:

ronaldrc

Senior Member
Location
Tennessee
A little more detail: The lights are 277V.........there are a roughly total of 150 poles throughout the park running parallel with the walk paths........so there will be multiple 120V circuits
If you go with the 3/0 your probably going to be using split bolts to make the taps or splices at the poles,or we always did, so just put your #12 in your split bolt with the 3/0 and use a 15 or 20 amp. in line fuse to protect your receptacle.
I assumed that's what you where going to do with the light?
 

Smart $

Esteemed Member
Location
Ohio
Perhaps another pertinent design detail...

How will the lighting be controlled? ...e.g. photocell on each pole or centrally switched by timer or photocell, or combination thereof.

What about control of the rcpts?

Ultimately, what I'm looking at is whether the lighting and receptacles can be on the same circuits....
 
Thanks guys. I think im going to provide a small 480-120V transformer for each pole. We aren't allowed to put anything the pole bases or directly on the pole....can I put the transformer in an accessible handhole close to (18"x24") im thinking 2kVa (overkill?)
 

Ragin Cajun

Senior Member
Location
Upstate S.C.
SquareD has small single phase trasformers with integral primary and secondary fuses, which you definitely need.

The problem is how to "enclose" them so there are no exposed live terminals, but allow heat to escape. I would be reluctant just relying on a sign on the hand hole saying exposed live 480V within, or some such.

Perhaps 1 KVA is more resonable than 2 KVA? Get firm input from the client as there is a cost issue. LED lights are one thing, plugging in an electric trimmer or such is another matter.

RC
 

Smart $

Esteemed Member
Location
Ohio
...can I put the transformer in an accessible handhole close to (18"x24") im thinking 2kVa (overkill?)
JMO, but I think you can... but I have to wonder if the handhole would be thus considered a transformer vault and have to comply with the ventilation requirement.

2kVA might be overkill. How much power is spec'd or do you want to provide???
 
Top