icc.codedude
Member
- Location
- California
A property owner wants to run power to 3 new lighting fixtures that is over 300 feet from the nearest panel. He wants to use #14 AWG on a 15 amp circuit. How does this affect wire and breaker sizing.
VOLTAGE DROP
- Thread starter icc.codedude
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Voltage drop is dependent on the load. What is the wattage of the fixtures? IMO the owner is out of his mind and depending on the fixtures this may not be enough to run the fixtures effectively
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
With just 5 amp load there would be a 6 volt drop at 120V using 14 awg-- That's about 5%--- again if the load was 10 amps you would have double the lose. It still may be compliant but not a good idea
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
It affects wire size, as Dennis has already mentioned. It does not affect breaker size. You could improve the voltage drop situation by using #12 wire, and still keeping the 15 amp breaker. But you would have to use #12 for the equipment grounding conductor, as well as for the hot and neutral wires. But it all comes down to total load. What size of lights (i.e., in terms of watts) is the owner planning to use? Are LED lights being considered?
kwired
Electron manager
- Location
- NE Nebraska
Depends on voltage too. If it were 277 volt lighting you can drop more volts then you can @ 120 volts and still be within a certain percentage.
icc.codedude
Member
- Location
- California
Voltage Drop
Voltage Drop
He will be using motion sensors, he considers them for security. Two 100 watts at each of 3 locations.
Voltage Drop
He will be using motion sensors, he considers them for security. Two 100 watts at each of 3 locations.
kwired
Electron manager
- Location
- NE Nebraska
100 watt incandescent? A little voltage drop will actually extend the life of those, but the motion sensor may or may not like any VD.
100 watt equivalent LED - equates to maybe 13 actual watts, not nearly as big of an impact on VD.
Carultch
Senior Member
- Location
- Massachusetts
On the bright side (no pun intended), if it's an incandescent fixture, he will have good bulb life
True, if the owner is OK with a dingy yellow-brown look to this lighting.
dfmischler
Senior Member
- Location
- Western NY
- Occupation
- Facilities Manager
Also, at the higher voltage and the same wattage the IR losses will be substantially less.
600 watts / 120 volts = 5 amps : 5 amps * 1.5 ohms (600 ft of 14 awg) = 7.5 volts dropped = ~6.25%
600 watts / 277 volts = ~2.2 amps : 2.2 amps * 1.5 ohms (600 ft of 14 awg) = 3.3 volts dropped = ~1.2%
Fitzdrew516
Senior Member
- Location
- Cincinnati, OH
If I were designing this I would use #8's (Assuming copper conductors @ 120V) to get it under the recommended 3% VD, but #10's would get you pretty close to that 3% as well. If you're using 277V then #14's would work, but I never use anything less than #12's for commercial jobs.
Also, I am running voltage drop considering the whole circuit's load. If you want to calculate series voltage drop you could likely get away with smaller wire sizes on the last couple runs of wire depending on the distances between each load.
junkhound
Senior Member
- Location
- Renton, WA
- Occupation
- EE, power electronics specialty
Unless this is a DIY homeowner job (2nd post?) there is negligible cost savings compared to the labor for installation (and trenching?).
Heck, even if DIY HO bootleg, the HO would want an outlet out there for future tasks so put in 10 AWG.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Spooky... Dennis guessed the exact load. :blink:
I agree with what others have written re: upsizing the wiring. There is about a 100$ difference between 14-2 UF and 10-2 UF with the length here. Not completely inconsequential for a small job, but if the HO wants more lights later, or an outlet at the last light, how much to retrench that 300' and run #10 or #8 then anyway.
John120/240
Senior Member
- Location
- Olathe, Kansas
Only You know the job situation. If it was me, PVC conduit with #8 or #6 THHN/THWN & set a 8 circuit panel.
- Location
- Massachusetts
It is interesting how different we all approach the same situation.
My approach would be to make my recommendation to the customer but I have no problem at all installing it exactly how they request it no matter how silly or impractical it might be. Of course within the requirements of the code.
I don't look at it like it is 'my work' it is the person who is paying the bills that owns the work and gets to decide how it is done.
JFletcher
Senior Member
- Location
- Williamsburg, VA
It is interesting how different we all approach the same situation.
My approach would be to make my recommendation to the customer but I have no problem at all installing it exactly how they request it no matter how silly or impractical it might be. Of course within the requirements of the code.
I don't look at it like it is 'my work' it is the person who is paying the bills that owns the work and gets to decide how it is done.
Never thought of it like that before. very helpful perspective; thank you.
There'd be an enormous difference in cost between that and using 14-2 in a trench, unless you're having to trench thru 18" of solid rock.
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