ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
Electrode boilers question
by annemarie1. 04/27/17 01:40 PM
Why cables look like they do
by LongRunner. 04/26/17 09:36 AM
Dimmable LED 2x4 lay in fixtures
by HotLine1. 04/24/17 05:43 PM
Old decora style outlets
by Lostazhell. 04/22/17 07:59 PM
Permit Snafus...AHJs and Contractors Jump in
by gfretwell. 04/22/17 01:11 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
234,863 Are you busy
169,656 Re: Forum
162,898 Need opinion
Who's Online Now
0 registered members (), 41 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#170854 - 11/13/07 09:15 PM Low voltage line loss  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
I'm running some long 12 Volt circuits to rope lighting and I'm needing to figure out the voltage drop. I have already put in 12-2 12 volt landscape wire. I need to find out what the resistance for this wire is. It seems to have more strands than stranded #12 so I don't think that Ohm value is what I want.

Any help?



Work Gear for Electricians and the Trades

#170863 - 11/13/07 10:04 PM Re: Low voltage line loss [Re: bwise121]  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Do you have any loss figures for the wire itself?
In that, usually there are stated losses for a given size of wire given as mV per Amp per metre (foot?) this is then used to calculate the total voltage drop of the circuit.
BTW, if you are trying to find the resistance of that wire, you'll be needing a low-ohm meter or a really accurate multi-meter.


Let's face it, these days if you're not young, you're old - Red Green grin

#170864 - 11/13/07 10:12 PM Re: Low voltage line loss [Re: Trumpy]  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
I have no intention of using a meter to calculate it myself. I know there are tables for cross-sectional are of conductors but like I said this wire is stranded with probably twice as many strands as #12 THHN stranded.


#170865 - 11/13/07 10:16 PM Re: Low voltage line loss [Re: bwise121]  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
I guess the question I'm really needing answered is does the voltage drop formula differentiate between stranded and solid wire.


#170867 - 11/13/07 10:40 PM Re: Low voltage line loss [Re: bwise121]  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
http://www.generalcable.com/NR/rdon...E3F73914A/0/Pg37_LwVltgLndscpLghtgWr.pdf

That is about as close to specs as I can get. It is one of the #12 wires toward the bottom. I still don't think any of that information will help.


#170877 - 11/13/07 11:32 PM Re: Low voltage line loss [Re: bwise121]  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
Something isn't right. Can someone advise me on this.
Ed = (12*I*L*2)/CMA

Ed is allowable voltage drop
I is amps
L is length in feet
and CMA is Circular Mils

In this case:
I = 13.3 (8 20 watt bulbs 12Volt)
L = 40'
CMA is 6530 for #12

This means that Ed is about 16%(1.955 volts).

I know from experience we have put many out door lights on a transformer and have had no problems (watts ? can't remember). What gives?




Member Spotlight
HotLine1
HotLine1
Brick, NJ USA
Posts: 6,809
Joined: April 2002
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.013s Queries: 15 (0.002s) Memory: 0.7771 MB (Peak: 0.9272 MB) Zlib enabled. Server Time: 2017-04-28 10:11:33 UTC