Parking lot, site lighting voltage drop requirement

anbm

Senior Member
Do we need to limit 3% voltage drop for exterior parking lot and site lighting even if they are LED lights?
Is this a code requirement? This will make a huge cost difference.
 
Pretty sure that voltage drop limitations are recommendations only, and are there to help ensure loads are operating efficiently and won't die prematurely, but it isn't considered a safety issue. Also, do you have a fairly even/symmetrical lot lighting layout so you can use center of load to calculate voltage drop, instead of calculating voltage drop to the furthest fixtures?
 

MAC702

Senior Member
Location
Clark County, NV
More info helps, also. For example, some LED fixtures might be already specified for a wide voltage range. There are also other ways to mitigate voltage drop without upsizing the conductors, assuming this is your concern.
 

cburke1111

Member
Location
Fort Myers
Pretty sure that voltage drop limitations are recommendations only, and are there to help ensure loads are operating efficiently and won't die prematurely, but it isn't considered a safety issue. Also, do you have a fairly even/symmetrical lot lighting layout so you can use center of load to calculate voltage drop, instead of calculating voltage drop to the furthest fixtures?
How do you do a center of load to voltage drop calculation?

Sent from my Pixel 2 XL using Tapatalk
 
How do you do a center of load to voltage drop calculation?

Sent from my Pixel 2 XL using Tapatalk
If you have multiple EQUAL loads, that are placed EQUALLY along the length of the circuit, find the center of the circuit based on the actual installation path that will be used. Calculate voltage drop to that point, instead of the furthest load. This takes advantage of the fact that the loads closer to the panel will have less voltage drop. That was explained to me by a really good electrical PE a few years ago when doing designs for big-box retail store parking lot lighting.
 

cburke1111

Member
Location
Fort Myers
If you have multiple EQUAL loads, that are placed EQUALLY along the length of the circuit, find the center of the circuit based on the actual installation path that will be used. Calculate voltage drop to that point, instead of the furthest load. This takes advantage of the fact that the loads closer to the panel will have less voltage drop. That was explained to me by a really good electrical PE a few years ago when doing designs for big-box retail store parking lot lighting.
Thank you

Sent from my Pixel 2 XL using Tapatalk
 

Fulthrotl

~~Please excuse the mess. Sig under construction~~
More info helps, also. For example, some LED fixtures might be already specified for a wide voltage range. There are also other ways to mitigate voltage drop without upsizing the conductors, assuming this is your concern.
yeah. some led drivers are 120~277 off of one tap.

they are gonna consume the wattage they are rated for,
irregardless of the voltage. if the voltage is low, and you
consume the same power, current will go up. if it goes over
the breaker rating, you will save a lot of power, at the expense
of illumination.

look at your driver cut sheets.
 

anbm

Senior Member
More info helps, also. For example, some LED fixtures might be already specified for a wide voltage range. There are also other ways to mitigate voltage drop without upsizing the conductors, assuming this is your concern.
Yes
 

anbm

Senior Member
yeah. some led drivers are 120~277 off of one tap.

they are gonna consume the wattage they are rated for,
irregardless of the voltage. if the voltage is low, and you
consume the same power, current will go up. if it goes over
the breaker rating, you will save a lot of power, at the expense
of illumination.

look at your driver cut sheets.
Are you talking about constant current drivers?
 

kwired

Electron manager
Location
NE Nebraska
Do we need to limit 3% voltage drop for exterior parking lot and site lighting even if they are LED lights?
Is this a code requirement? This will make a huge cost difference.
Unless you have an energy code or other NEC amendments to comply with, the 3% that is mentioned in NEC is in an informational note and is just that - information (suggestive information in this case).

i'm talking about a 27 watt driver, with an input voltage of 120~277, for example.

it's gonna pull 27 watts with a power source between those voltages.
it's gonna take more current with less voltage to get 27 watts.
More current means more voltage drop which makes current go up even further - until there is a balance. Also means more line losses.
 
Top