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View Full Version : How do you calculate voltage drop???


djt22
07-21-2011, 04:46 PM
How do you calculate your voltage drop and do you do different methods depending on what transformer you use?

The Lighting Geek
07-21-2011, 06:29 PM
Well, it just so happens I had to brush up on this very thing to pass my CLVLT test last weekend. The formula most people use is: watts x length of wire in feet, divided by the wire constant, X 2 (because it is AC)

The constants are:
16/2: 2200
14/2: 3500
12/2: 7500

OK, did I get that right? LOL
TRUST ME, if I am incorrect someone will correct me. :-)

Richie@
07-22-2011, 06:42 AM
How do you calculate your voltage drop and do you do different methods depending on what transformer you use?

Here is an online calculator that will get you close, Cast also has a calculator.

http://www.residential-landscape-lighting-design.com/calculator.asp

steveparrott
07-22-2011, 11:59 AM
How do you calculate your voltage drop and do you do different methods depending on what transformer you use?

Tommy's formula is essentially correct for a single wire run with a single fixture or multiple fixtures connected with a hub or Spider Splice.

For more complicated calculations, I suggest you use one of these CAST calculators:

CAST System Calculator (http://www.cast-lighting.com/calculator/volt-calc.html) - for Spider Splice Method
CAST Daisy Chain System Calculator (http://www.cast-lighting.com/search/1/display-document/146)- Beta Excel version that allows you to calculate daisy chain systems or combination method systems. Allows you to factor in power factors for LED's.