wiring in conduit for long driveway


  #1  
Old 10-28-02, 04:16 PM
D
Member
Thread Starter
Join Date: Mar 2001
Location: Connecticut
Posts: 712
Upvotes: 0
Received 0 Upvotes on 0 Posts
wiring in conduit for long driveway

When we built our house 2 years ago, we had a conduit (1 1/2") run from the house down the entire driveway (about 650 feet). We just intend to light 2 lights on pillars (about 120 watts total) plus maybe 6 0r 7 low voltage lights along the edge of the driveway. What gauge wire would people recommend due to this length of run e.g. 12 gauge? Also, would it be ok to use Romex? I know for bigger applications in conduit romex is not recommended due to inability to dissipate heat. How about in this setting? We have a pull rope in place. Would it be possible with a helper feeding the wire to pull it 650 feet by hand, or will we need a winch?
Thanks.
Dave
 
  #2  
Old 10-28-02, 04:36 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
14-gauge wire is sufficient for one amp (120 watts). Tell me the wattage of those 6 or 7 low voltage lights to see if 14-gauge is still sufficient once you add those. If the low voltage lights add up to 100 watts or more, go up to 12 gauge.

You can use Romex if you want, but not "NM" Romex, only "UF" Romex.

Or you can use individual THWN wires. The individual wires will be much easier to pull.
 
  #3  
Old 10-31-02, 02:29 PM
hornetd's Avatar
Member
Join Date: Aug 2001
Location: Maryland
Posts: 646
Upvotes: 0
Received 0 Upvotes on 0 Posts
Use Edison circuit to reduce voltage drop.

Do yourself a favor and run four wires. One bare or green and one each white, black, and red THWN. Supply the load from a multi wire branch circuit 120/240 volt. Use a two pole switch to turn both legs on and off at the house. Using that type of circuit will help with voltage drop problems.
--
Tom
 
  #4  
Old 11-16-04, 01:32 PM
D
Member
Thread Starter
Join Date: Mar 2001
Location: Connecticut
Posts: 712
Upvotes: 0
Received 0 Upvotes on 0 Posts
Are you saying to run a black and red as power and the white as neutral?
How would I wire the fixtures in this case (5-6 flood lights)?
 
  #5  
Old 11-16-04, 02:20 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
Tom is suggesting a multiwire circuit. You would wire every other light to black and white, and every other light to red and white. This, however, introduces some complications, especially with GFCI, and my require you to bury your cable deeper than otherwise.
 
  #6  
Old 11-16-04, 04:32 PM
D
Member
Thread Starter
Join Date: Mar 2001
Location: Connecticut
Posts: 712
Upvotes: 0
Received 0 Upvotes on 0 Posts
Say I want to have a total of 7 fixtures for a max of 400 watts. At the distance I have (650-700 feet to the last fixture), what would you use gauge and wire type. I was thinking of THWN in the conduit. Would 12 gauge wire be sufficient? Or could I go with Romex 12-2 UF?
Is it true you can't use NM in conduit...I guess because it can still get wet.
 
  #7  
Old 11-16-04, 04:38 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
To do an accurate calculation, tell us the distance not only to the last light, but to all the other lights too. I assume you're talking about seven 60-watt bulbs.

Are we still talking low-voltage fixtures? I hope not.

Are we talking about incandescent bulbs?

How difficult is digging in your area? Do you have some way to reasonably dig a 700-foot trench?
 
  #8  
Old 11-16-04, 05:41 PM
D
Member
Thread Starter
Join Date: Mar 2001
Location: Connecticut
Posts: 712
Upvotes: 0
Received 0 Upvotes on 0 Posts
The conduit is already in place with a pull rope in it....so no digging.
The first light would be about 300 feet from the house. the last would be about 700 feet.
I was thinking of 7 50-60 watt incandescent fixtures (120 v).
 
  #9  
Old 11-16-04, 06:01 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
Let's assume you have seven 60-watt bulbs at 300, 367, 433, 500, 567, 633, and 700 feet. The first 300 feet carry 3.5 amps, but the last 67 feet carries only 0.5 amps. So let's say you use #12 copper wire (two plus ground). The first bulb will get 116 volts. The last light will get 114 volts. The lights in between will get somewhere in between. Since incandescent bulbs don't care much about small voltage differences, the #12 should be just fine.

Do not, I repeat do not, be tempted to put a receptacle out at the end of this line!

And do not use a cable. Use dual-rated THHN/THWN individual wires.
 
  #10  
Old 11-16-04, 06:25 PM
Speedy Petey's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2003
Posts: 2,262
Upvotes: 0
Received 0 Upvotes on 0 Posts
Just an opinion from someone who does a lot of 500'-1000' driveways.
Run #10, or even #8, and use THWN conductors not NM cable.
I am not normally one for extreme overkill, like #10 for inside receptacles, but for this distance the added size of wire is justifyable protection.
There may someday be the temptation to add something or replace the lights with something larger.
 
  #11  
Old 11-17-04, 10:13 AM
D
Member
Thread Starter
Join Date: Mar 2001
Location: Connecticut
Posts: 712
Upvotes: 0
Received 0 Upvotes on 0 Posts
John,
Just for curiosity sake, why did you say not to place a recpetacle at the end of the run? Is it because of decrease in voltage?
 
  #12  
Old 11-17-04, 02:23 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
If you use 12-gauge wire as I suggested, you don't have enough voltage left at the end to plug anything in out there. So don't provide the temptation.

Speedy has anticipated that the temptation will be too great, and has suggested you plan for it.
 
  #13  
Old 11-17-04, 03:14 PM
D
Member
Thread Starter
Join Date: Mar 2001
Location: Connecticut
Posts: 712
Upvotes: 0
Received 0 Upvotes on 0 Posts
OK, this poses an interesting question. Last year, I ran some UF wire to a hook up a mercury vapor light near our pond. The total length from the switch is about 200 feet. At the time, I thought I was being so smart, and I placed a GFCI receptacle out there. I went tonight to check it, and I get between 118.6 and 119 volts. What is considered too low as far as voltage goes. Does it change the voltage whether the light is on or not? That voltage was with the light on.
Thanks.
Dave
 
  #14  
Old 11-17-04, 03:19 PM
R
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,245
Upvotes: 0
Received 0 Upvotes on 0 Posts
The voltage you get with your meter is not important, because you don't have a load out there. The higher your load, the greater the voltage drop.

What do you intend to use at the end of this run, and what is the power requirement of the existing light?
 
  #15  
Old 11-17-04, 03:44 PM
J
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 8,060
Received 521 Upvotes on 426 Posts
Originally Posted by Dave4242
I went tonight to check it, and I get between 118.6 and 119 volts. What is considered too low as far as voltage goes. Does it change the voltage whether the light is on or not? That voltage was with the light on.
Thanks.
Dave
Anything down to 110volt should be safe for any device. The more load you put at the end of the run the lower the voltage will be. Try measurement again with the light on.
 
  #16  
Old 11-17-04, 05:38 PM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 17,733
Upvotes: 0
Received 1 Upvote on 1 Post
Even measuring it with the light on is insufficient. Plug in something and turn on something you might use that receptacle for, such as a weed wacker or hedge clipper or shop vacuum. Measure the voltage with the light on and the appliance running.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: