Voltage Drop

[jap]

There is a park in our town that has a 1/3 mile walking trail around it.
Recently they have installed (16) 240v Decorative Lamp Post with 150w MH Lamps approximately every 100' around the outside of the trail.
I noticed when they were installing the conduit stubouts from the pole standards they were all 3/4" pvc & was wondering how that would be large enough for the Conductors they would have to pull to satisfy the voltage drop. Each light pole has a gfi receptacle mounted on it. The (8) East poles are feed off a 2p 20a breaker with #10 Thhn for the Fixtures and (1) 1p 20a breaker Feeds (8) of the gfi receptacles mounted on the poles.The same goes for the West Side Poles and Receptacles.I dont see how the #10 wire is sufficient to carry the load when the farthest outlet is 800' away from the source, but everything seems to work fine.How do you determine the load for the receptacles if you dont know what the load will be? If there was a 16 amp load at the farthest GFI I come up with almost a 32 volt drop. Am I looking at this the wron way?

 

[lakee911]

I thought that limiting voltage drop was only a suggestion and not a requirement?

Perhaps the far out lights are being run at 208?

If the lamp lights, the cost of upsizing the conductor, conduit and labor may be far more than they would recooperate over the long term with elec bill savings.

 

[A/A Fuel GTX]

I think the determining factor for the receptacles is their intended use. Probably holiday lighting and not hole hawgs. That being said, I would think a string of miniature lights on each pole would work out fine without any VD issues. As far as the HID's go, sounds like an acceptable install there also....IMHO.

 

[kacper]

There is a park in our town that has a 1/3 mile walking trail around it.
Recently they have installed (16) 240v Decorative Lamp Post with 150w MH Lamps approximately every 100' around the outside of the trail.
I noticed when they were installing the conduit stubouts from the pole standards they were all 3/4" pvc & was wondering how that would be large enough for the Conductors they would have to pull to satisfy the voltage drop. Each light pole has a gfi receptacle mounted on it. The (8) East poles are feed off a 2p 20a breaker with #10 Thhn for the Fixtures and (1) 1p 20a breaker Feeds (8) of the gfi receptacles mounted on the poles.The same goes for the West Side Poles and Receptacles.I dont see how the #10 wire is sufficient to carry the load when the farthest outlet is 800' away from the source, but everything seems to work fine.How do you determine the load for the receptacles if you dont know what the load will be? If there was a 16 amp load at the farthest GFI I come up with almost a 32 volt drop. Am I looking at this the wron way?

Wires sizing based only on allowable ampacities of conductors without considering voltage drops required by table 8 in Chapter 9 or 310.15(B)(2)(a), may cause a serious of uncontrolled problems from overheating, melting to a fire included.
Section 90.5 (C) page 6 of the NEC states??Footnotes to tables, although also in fine print, are NOT explanatory material unless they are identified by the abbreviation FPN. However table footnotes are part of the table and are necessary for proper use of the tables.?
My rough calc. indicate # 8 requirements.

 

[iwire]

Wires sizing based only on allowable ampacities of conductors without considering voltage drops required by table 8 in Chapter 9 or 310.15(B)(2)(a), may cause a serious of uncontrolled problems from overheating, melting to a fire included.

Can you provide an example of how that would happen in a code compliant circuit?

Section 90.5 (C) page 6 of the NEC states…”Footnotes to tables, although also in fine print, are NOT explanatory material unless they are identified by the abbreviation FPN. However table footnotes are part of the table and are necessary for proper use of the tables.”
My rough calc. indicate # 8 requirements.

Are you suggesting the NEC requires that voltage drop be considered at all for the circuit this thread is about?




jap

You could gain a lot just by using a multiwire branch circuit, if you only have single phase run the circuit to each fixture like this A-B-A-B-A-B

If you have 3 phase available go A-B-C-A-B-C.

If you do that I am willing to bet 10 AWG will work fine. Keep in mind that the EGC run with this circuit must be the same size as the circuit conductors. Also by alternating the circuits the light output will be more uniform along the circuit.