Voltage Drop And Conductor Size

 
Thread Tools Search this Thread Display Modes
Old 02-10-2009, 07:37 PM   #1
Electrical Contractor
 
TinkerGA's Avatar
 
Trade: electical contractor
Join Date: Feb 2009
Location: Blairsville,GA
Posts: 5
Rewards Points: 10

Voltage Drop And Conductor Size


I am new to this site,love the comments.Have a question because I have never had such a long pull. Customer wants 9 (3 lamp) (60 watt) 120volt outdoor lights on 1 switch. Power source to first light is 42ft then 70ft,70ft,70ft,30ft,30ft,70ft,70ft,70ft for a total of 522ft. What size wire do I run? Will a 10AWG on a 30amp breaker be enough.I figured the voltage drop by length and amps betwwen each light. first light 42ft at 13.5amps second 112ft at 12amps third 182ft at 11.5 and so on using 120volts as a base even though PoCO VOLTAGE varies. Would like some feed back or good way to calculate.Still trying to learn.
TinkerGA is offline  

Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ContractorTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

   

Advertisement

 

Old 02-10-2009, 07:43 PM   #2
Member
 
walkerj's Avatar
 
Trade: Electrical
Join Date: May 2007
Location: Louisiana
Posts: 43
Rewards Points: 25

Re: Voltage Drop And Conductor Size


If this is a house, the lights most likely can't be installed on a 30 amp circuit.

#10's and a 20 amp breaker would probably work fine, but you could use #8's to the first light if it made you feel warm and fuzzy.

Advertisement

walkerj is offline  
Old 02-10-2009, 08:25 PM   #3
Service & Repairs
 
Magnettica's Avatar
 
Trade: Electrician
Join Date: Dec 2006
Location: Rahway, New Jersey
Posts: 4,001
Rewards Points: 2,002

Re: Voltage Drop And Conductor Size


Here's an online calculator for voltage drop: http://www.elec-toolbox.com/calculators/voltdrop.htm
Magnettica is offline  
Old 02-10-2009, 08:41 PM   #4
Electrical Contractor
 
Speedy Petey's Avatar
 
Trade: Electrical
Join Date: Sep 2003
Location: NY State
Posts: 2,345
Rewards Points: 1,082

Re: Voltage Drop And Conductor Size


The calculator Mag linked is the one I like to use.

Guess what, for 522', @ 120v, @ 13.5A it is calling for #3. I know the load is incremental, but you still have a 120v load at 522'.
I'd say at least #6.

Can he use CFLs to lessen the total wattage?
__________________

Speedy Petey is online now  
Old 02-10-2009, 08:58 PM   #5
Pro
 
nap's Avatar
 
Trade: sparky
Join Date: Jan 2008
Location: SW Michigan
Posts: 591
Rewards Points: 500

Re: Voltage Drop And Conductor Size


Quote:
Originally Posted by Speedy Petey View Post
The calculator Mag linked is the one I like to use.

Guess what, for 522', @ 120v, @ 13.5A it is calling for #3. I know the load is incremental, but you still have a 120v load at 522'.
I'd say at least #6.

Can he use CFLs to lessen the total wattage?
Petey, what's the rules for running 240 for lights in resi? any problems?

If not, if Tinker can get 240 rated lights/fixtures (I know, luminaires (God I hate the new terminology with 12mm conduit and luminaires and all)).

that would drop the current so the voltage drop would require a much smaller conductor increase.

What do ya think?
nap is offline  
Old 02-10-2009, 09:36 PM   #6
Service & Repairs
 
Magnettica's Avatar
 
Trade: Electrician
Join Date: Dec 2006
Location: Rahway, New Jersey
Posts: 4,001
Rewards Points: 2,002

Re: Voltage Drop And Conductor Size


Quote:
Originally Posted by Speedy Petey View Post
The calculator Mag linked is the one I like to use.

Guess what, for 522', @ 120v, @ 13.5A it is calling for #3. I know the load is incremental, but you still have a 120v load at 522'.
I'd say at least #6.

Can he use CFLs to lessen the total wattage?
I probably got the link from you!
Magnettica is offline  
Old 02-10-2009, 09:45 PM   #7
Electrical Contractor
 
Speedy Petey's Avatar
 
Trade: Electrical
Join Date: Sep 2003
Location: NY State
Posts: 2,345
Rewards Points: 1,082

Re: Voltage Drop And Conductor Size


240v lights would help VD, but if he wants to use standard lamps that becomes a real issue.
He could use a multi-wire circuit to help lessen VD.
__________________

Speedy Petey is online now  
Old 02-10-2009, 10:17 PM   #8
Pro
 
nap's Avatar
 
Trade: sparky
Join Date: Jan 2008
Location: SW Michigan
Posts: 591
Rewards Points: 500

Re: Voltage Drop And Conductor Size


I didn't know if they even made such buggers or not.

maybe some small HID fixtures would serve the purpose.


Is Marc back from France yet? Maybe he could bring over some 240 rated 60 watt incandescents and voltage rated sockets.



or how about a nap special install;

2-120 volt lamps in series. and then each group of 2 paralleled as normal.
nap is offline  
Old 02-10-2009, 10:21 PM   #9
Electrical Contractor
 
TinkerGA's Avatar
 
Trade: electical contractor
Join Date: Feb 2009
Location: Blairsville,GA
Posts: 5
Rewards Points: 10

Re: Voltage Drop And Conductor Size


Thanks for the comments. I tried to get the customer to get 240v lights but he likes the ones he's already bought.I done the voltage drop calculation at first with 13.5amps at 522ft and got a #3 but that seems to be over kill then in increments and really a #10 seems to small , maybe I will go with a #6 just to be on the safe side.
TinkerGA is offline  
Old 02-11-2009, 12:29 AM   #10
Pro
 
nap's Avatar
 
Trade: sparky
Join Date: Jan 2008
Location: SW Michigan
Posts: 591
Rewards Points: 500

Re: Voltage Drop And Conductor Size


I would either act according to the voltage drop calc's or you are going to be responsible for any problems that may arise.
alternative; letting the (untrained and therefore, ignorant) customer make the call.

The only problem should be dim lights but depending on the exact circuit it can vary.
nap is offline  
Old 02-11-2009, 12:29 AM   #11
Pro
 
mickeyco's Avatar
 
Trade: Squirrel Handler
Join Date: May 2006
Location: Chicago
Posts: 3,432
Rewards Points: 2,000

Re: Voltage Drop And Conductor Size


Quote:
Originally Posted by Speedy Petey View Post
240v lights would help VD, but if he wants to use standard lamps that becomes a real issue.
He could use a multi-wire circuit to help lessen VD.
Question, how about a double pole switch ("on 1 switch") on a multi-wire, alternating the lights?




.

Advertisement

__________________
Some people climb mountains. I take out the trash. But we both do it for the same reason.
mickeyco is offline  


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Join Now... It's Fast and FREE!

I am a professional contractor
I am a DIY Homeowner
Drywall Talk is for
PROFESSIONAL CONTRACTORS ONLY!

At DrywallTalk.com we cater exlusivly to professional contractors who make their living as a contractor. Knowing that many homeowners and DIYers are looking for a community to call home, we've created www.DIYChatroom.com DIY Chatroom is full of helpful advices and perfect for DIY homeowners.

Redirecing in 10 seconds
No Thanks
terms of service

Already Have an Account?