ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
AFDD's coming to the UK
by Texas_Ranger. 02/18/19 02:04 PM
by Texas_Ranger. 02/18/19 02:01 PM
by gfretwell. 02/16/19 01:08 PM
PurpleAir Recalls Power Supply Units
by Admin. 02/14/19 08:43 PM
Utility Company Programs
by katty81. 02/14/19 11:11 AM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
1 registered members (gfretwell), 10 guests, and 28 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 5 1 2 3 4 5
Post light Feed #64490
04/08/06 09:28 AM
04/08/06 09:28 AM
ToHo  Offline OP
Joined: Dec 2004
Posts: 46
I have a bid on residential post lighting job.The customers driveway is 1200 ft long. He wants 10 post lights installed. I figure 100w per post light.Trying to achieve 3% vd, I'm looking at #2 copper for the run. My question is about the what size breaker to use.Base the breaker size on the load ? Also the customer want a receptacle 1000' up the drive way. I can use the same feed but splicing smaller conductors to feed the outlet ? Any help as always is greatly aprreciated.

Work Gear for Electricians and the Trades
Re: Post light Feed #64491
04/08/06 10:43 AM
04/08/06 10:43 AM
Alan Nadon  Offline
Joined: Mar 2005
Posts: 399
Elkhart, IN. USA
I can't help with your design. Conflict of interest,but you are on the right track. Having seen similar installations the voltage drop is only on the main run. At the breakers and the loads, splice / branch to smaller conductors. The few feet at that point will not affect voltage drop. What ever you do, do NOT trim strands off the #2 to make it fit in a terminal.
Good Luck.

If it was easy, anyone could do it.
Re: Post light Feed #64492
04/08/06 11:26 AM
04/08/06 11:26 AM
winnie  Offline
Joined: Sep 2003
Posts: 649
boston, ma
I would suggest considering a multi-wire-branch-circuit for this load. If you put 5 posts on each leg, alternating, then you could use #8 conductors and meet your voltage drop requirements.

Remember to increase the size of the equipment grounding conductor at the same time that you upsize the supply conductors.

If you place the receptacle on this circuit, then you are limited to using 20A breakers.


Re: Post light Feed #64493
04/08/06 11:43 AM
04/08/06 11:43 AM
Tiger  Offline
Joined: May 2005
Posts: 706
Crystal Lake, IL USA
This may not be helpful, but as a reality check. If this is out for bids, the other contractors will probably be bidding the job in 12 ga. wire. While the voltage will drop beyond 3%, you can buy a lot of 100W bulbs for the price of wire you're planning (won't the low voltage actually make the bulbs last longer?).

If this is your job, then I'm all for doing it right. If it's not, good luck selling the benefit of low voltage drop at a major increase in cost.


Re: Post light Feed #64494
04/08/06 12:31 PM
04/08/06 12:31 PM
Larry Fine  Offline
Joined: Feb 2005
Posts: 693
Richmond, VA
ToHo, you don't have to make the entire run the full-sized conductors. The trick to doing the voltage-drop figuring is to work from the end back toward the source.

Figure the voltage drop one load at a time. In other words, keep in mind that the last run only carries 100 watts, the next-to-last run 200, etc. Step up in wire size only when you need to.

I agree completely with Winnies suggestion of a multi-wire circuit, alternating hots. If the customer wants the recetacle always-hot, run a separate circuit, and use a GFCI receptacle, not breaker.

Larry Fine
Fine Electric Co.
Re: Post light Feed #64495
04/08/06 12:35 PM
04/08/06 12:35 PM
Larry Fine  Offline
Joined: Feb 2005
Posts: 693
Richmond, VA
Why, you ask? Becuase you'll have nuisance-tripping calls you won't believe. GFCI breakers don't play well with long runs, especially underground, I found out the hard way.

Larry Fine
Fine Electric Co.
Re: Post light Feed #64496
04/08/06 12:40 PM
04/08/06 12:40 PM
Dave T  Offline
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
Interesting challenge.
Judging form that 1200'drive the customer may not be living on a shoestring so you may have an opportunity to do a sales job selling him on the BEST solution to his project, approaching it differently from your competitors. You could provide him with (2-3) options, with incandescent lights with cable priced to deal with voltage drops, fluorescent lighting with applicable cable, and an alternate with the 480v distribution.
If your customer likes your idea what you don’t want to do is to have him use it against you and ask your competitors for a requote.
Increasing the cable size to reduce the resistance in order to reduce the voltage drop is one consideration. Have you taken into account the cost of the cable and the cost of a means to terminate it?
When you made reference to (10) 100w one thinks about standard incandescent lights. Have you considered fluorescent lights which could provide the same light output but a lower wattage? With lower wattage there would be less voltage drop.
Then, that cable will cost a fortune the combine that cost with the grief with terminating it. Have you though about trading the cost of all of the heavy cable for a 1500va 480v-240v transformer used to step-up the voltage to 480v to distribute the power a 480v, install a 150va 480-120V transformer to step down the power at each lamppost. Just think, 1/4th the current to deal with. So smaller cable and less voltage drop.

Re: Post light Feed #64497
04/08/06 03:42 PM
04/08/06 03:42 PM
mhulbert  Offline
Joined: Oct 2004
Posts: 132
Anaheim, CA USA
How about this:

Distribute at 240V, use compact floursecent fixtures (26W should be about the same light as a 100w incandescent, with a lot less maintenance and energy!). Use electronic multi-Volt ballasts, which don't care as long as the voltage is between 120-277

Re: Post light Feed #64498
04/08/06 03:58 PM
04/08/06 03:58 PM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Use electronic multi-Volt ballasts, which don't care as long as the voltage is between 120-277

I do not believe you will find that these ballasts will be listed for use 'line to line'.

I also do not believe that the ballasts are listed 120 through 277.

There are listed 120 or 277.

Just because it may work does not mean it is a good idea or safe.

Bob Badger
Construction & Maintenance Electrician
Re: Post light Feed #64499
04/08/06 03:59 PM
04/08/06 03:59 PM
caselec  Offline
Joined: Apr 2002
Posts: 558
San Jose, CA
I would recommend using Jon’s suggestion of a multi-wire circuit. Pulling one additional wire will change your 8.3 amp 120 volt circuit into a 4.2 amp 240 volt circuit. I haven’t done any calculations but would guess you could get away with #8 or even #10 conductors and be within your desired 3% voltage drop. Make sure you calculate each segment of the circuit not the full load at 1200’. This would take care of the lights but not the receptacle. You really need to know what is going to get connected to the receptacle to figure the drop. The customer might be willing to forget the receptacle if they realizes how much additional the larger wire will cost. If they definitely want the receptacle I would consider running a separate circuit just for it which will save splicing the larger conductors at each light.


Curt Swartz
Page 1 of 5 1 2 3 4 5


2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Posts: 165
Joined: March 2007
Show All Member Profiles 
Top Posters(30 Days)
Admin 7
Popular Topics(Views)
253,245 Are you busy
189,886 Re: Forum
179,597 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.029s Queries: 15 (0.004s) Memory: 1.0308 MB (Peak: 1.2078 MB) Zlib enabled. Server Time: 2019-02-19 07:13:54 UTC