


Thread Tools  Display Modes 
10162007, 06:55 PM  #1 
Member
Join Date: May 2007
Posts: 56
Rewards Points: 75

Wattage vs. wire size
Is there a formula for this? as based on 120v system.
Advertisement 
10162007, 07:01 PM  #2 
Electrical Contractor
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,747
Rewards Points: 88

P=I*E
Where P=power in watts I=amps E=volts Code states. 14 awg=15amps max 12 awg=20 amps max 10 awg=30 amps max Advertisement
__________________
"The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care" Last edited by jbfan; 10162007 at 07:04 PM. Reason: add more info 
10162007, 07:12 PM  #3 
Member
Join Date: May 2007
Posts: 56
Rewards Points: 75

First, thanks for the reply.
So, If I have this right, then the max. wattage for a 120v, with #12 is: Watts(X)=20*120 X= 2400 is this correct? 
10162007, 07:14 PM  #4 
Electrical Contractor
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,747
Rewards Points: 88

Yep! More letters to make the post long enough!!!
__________________
"The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care" 
10162007, 07:19 PM  #5 
Electrician philosopher
Join Date: Aug 2007
Location: Lilburn, GA
Posts: 838
Rewards Points: 500

Ohms law
Just for fun, lets say I wanted to put 28 recessed cans in my big pimp kitchen and I was going to use 65 watt bulbs.
I=p/e or (28x65)/120 or i=15.17Amps In this case I would have to use 12 AWG CU wire. Or... lets say I had a 8000watt (or 8kw) heater that operated on 240Volts. I=p/e or 8000/240 or I=33.3Amps In this case I would have to use 8 AWG CU wire. Ohms law is extremely cool even for DIYers to wow your friends at cocktail parties with your knowledge of electrical theory! p=watts e=volts i=amps r=resistance If the electrician knows any two of these he/she can solve for the rest. And I was the kid in the eighth grade bi###ing about the fact that i'm never gonna need this algebra crap EVER! 
10162007, 07:21 PM  #6 
Member
Join Date: May 2007
Posts: 56
Rewards Points: 75

Thankyou there, jbfan.

10162007, 07:22 PM  #7 
Electrical Contractor
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,747
Rewards Points: 88

If the electrician knows any two of these he/she can solve for the rest. And I was the kid in the eighth grade bi###ing about the fact that i'm never gonna need this algebra crap EVER!
And I thought that was me!!!! Andy, When you taking the test?(Sorta of topic)
__________________
"The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care" 
10162007, 07:29 PM  #8 
Electrician philosopher
Join Date: Aug 2007
Location: Lilburn, GA
Posts: 838
Rewards Points: 500

I've got 7 years resi., one year comm. and I'll sit for the GA test in fall of 08 before GA adopts the 08 code. Thanks for asking! I've become a huge code geek just in the last 18 mos.

10162007, 07:33 PM  #9 
Electrical Contractor
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,747
Rewards Points: 88

I took mine in 96 in at the Gwinnett civic center.
Good luck.
__________________
"The problem isn't that Hillary Clinton lies. We all know she lies. The problem is that her supporters don't seem to care" 
10162007, 11:30 PM  #10  
Once fried, twice shy.
Join Date: Sep 2007
Location: Thailand
Posts: 251
Rewards Points: 250

Quote:
P(kW) = E(v) x I x Cos phi (this is for single phase power). I = P divided by (E x Cos phi) = 8 000 divided by (240 x 0.8) = 8 000 divided by 192 = 41.7 Amps. When calculating power consumption of equipment, the Power Factor must be considered if the equipment is inductive or capacitive. This formula, P = E x I, is for finding single phase Apparent Power (VA). The formulae for finding True Power (kW) is; P = E x I x Cos phi (single phase). P = 1.732 x E x I x Cos phi (3 phase).
__________________
Switchboard design engineer & Licensed Electrician (Australia). 

10172007, 02:48 PM  #11 
Electrician philosopher
Join Date: Aug 2007
Location: Lilburn, GA
Posts: 838
Rewards Points: 500

You are totally correct.

10172007, 04:32 PM  #12 
UAW SKILLED TRADES
Join Date: Jan 2007
Location: Kansas
Posts: 5,341
Rewards Points: 2,652

Andy's heater had a pf of 1.0.......
Advertisement
__________________
" One nice thing about the NEC articles ... you have lots of choices" Stubbie 
Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Wire size for distance Question  fburke  Electrical  4  07282007 10:29 AM 
Wire Size Help400ft line to pond for fountain  brownie47854  Electrical  14  04222007 01:50 PM 
Old house, new light fixture, too many wires  Persephonee  Electrical  3  01152007 09:58 AM 
Wire size for Central Air  mwtuck  HVAC  2  12012006 06:06 PM 
wire size wire to 10kw furnace?  lochcarron  Electrical  1  04102005 08:43 PM 