Low Voltage Calculations - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Low Voltage calculations
 User Name Remember Me? Password
 Register Blogs Articles Rewards Search Today's Posts Mark Forums Read

 Thread Tools Display Modes
01-02-2011, 12:17 PM   #1
Newbie

Join Date: Jan 2011
Posts: 1
Rewards Points: 10

Low Voltage calculations

I want to double check my calculations for low voltage lighting. I Have a 15 amp circuit, with some outdoor 110v floods on it. With everything on, it draws 7.4 amps. I would like to T off the junction box with a line to a transformer to run some 12v deck lighting. I want to make sure I am under my max amps of 15.

The deck lighting I want to run, as I said is 12v. The fixtures are as follows:

15 x 11 watt fixtures
12 x 7 watt fixtures.

How many amps will I draw in addition to the 7.4A already on this 15A circuit? I calculated about 2.5 amps in addition to my 7.4, which puts me at about 10A on a 15A circuit.

Thanks

01-02-2011, 02:01 PM   #2
A "Handy Husband"

Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 7,291
Rewards Points: 4,142

You are adding a total of 249 watts of lighting or 20.75 amps at 12 volts. Assuming the lighting transformer is only 80% efficient (very worst case), that's about 2.6 amps at 120 VAC.

7.4 (existing load) + 2.6 (added) = 10 amps total

__________________
Location:
Coastal South Carolina

03-31-2011, 04:46 PM   #3
Newbie

Join Date: Mar 2011
Posts: 5
Rewards Points: 10

Another way to calculate

I take the 12V wattage and divide by 120 to get the amps the low voltage lighting is using. 249 watts / 120 is a little over 2 amps.

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Spikeyboy Electrical 13 10-15-2010 12:03 PM TITAN2390 Electrical 4 10-07-2010 08:44 PM hyunelan2 Electrical 0 10-12-2009 01:25 PM WShawn Electrical 7 08-19-2008 07:22 AM jambud Electrical 17 03-12-2008 10:31 AM

Top of Page | View New Posts