Watts=Volt * Amp

Reply

  #1  
Old 01-16-01, 11:47 AM
Member
Thread Starter
Join Date: Jan 2001
Location: Michigan
Posts: 52
Received 0 Votes on 0 Posts
how many lightbults I allow to install under this condition?

volt 120
amp 15A
light 100w

Thanks
T Ran
 
Sponsored Links
  #2  
Old 01-16-01, 12:04 PM
Member
Join Date: Dec 1999
Location: Fort Mohave, AZ
Posts: 99
Received 0 Votes on 0 Posts
I get 18.

Each bulb draws 100 watts/120 volts = 5/6 amp.
15 amp/ 5/6 amp = 18 bulbs.

To check.

18 X 100 watts = 1800 watts

1800 watts / 120 volts = 15 amps.
 
  #3  
Old 01-16-01, 06:00 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
I get 14.

You can only use 80% of the circuit capacity for lights.
 
  #4  
Old 01-17-01, 06:25 AM
Member
Join Date: Dec 1999
Location: Fort Mohave, AZ
Posts: 99
Received 0 Votes on 0 Posts
I agree with you John. When I posted the response, I was only thinking about the pure circuitry. Yes, it must be down-graded by what you say, I was going to repost but didn't get around to doing it. Thanks for you correction.
 
  #5  
Old 01-17-01, 08:57 AM
Member
Thread Starter
Join Date: Jan 2001
Location: Michigan
Posts: 52
Received 0 Votes on 0 Posts
Smile

Thank you pink and John.
 
  #6  
Old 01-17-01, 06:46 PM
Wgoodrich
Visiting Guest
Posts: n/a
Reducing the load to 80% is a good idea.

However if these lights are installed in a dwelling you are allowed to load that circuit to 100% by the NEC because they are general lighting.

These lights would be considered non contiuous loads, in the eyes of the NEC.

Wg

 
  #7  
Old 01-17-01, 07:19 PM
Guest
Visiting Guest
Posts: n/a
A matter of degree.

Hi,

I eagerly read these answers as a student of wiring, loosely speaking. I was excited to hear the 80 percent rule that I had learned before, thus good reinforcement in my DIY training! Then, I was even more wide-eyed as I read the 100 percent rule in the case of 'general lighting'! This is the kind of stuff I drool over to learn! Subtle, yet useful reasons behind the complexities of building codes.

Thanks everyone!
 
  #8  
Old 01-17-01, 07:46 PM
Wgoodrich
Visiting Guest
Posts: n/a
Mark please understand that everywhere is considered continuous except dwellings.

Single family dwellings, and inside apartments inside only, and inside hotel rooms for sleeping or living only, and inside motel rooms for sleeping or living only.

If you go out of a motel room then the lights in that hall is considered to be continuous.

Any wiring that runs more than 3 hours is considered as continuous.

The NEC states that inside the areas mentioned are for habatation and the general lighing is considered to be not continuous, even receptacles in these living areas are not considered to be continuous. However remember special receptacles such as laundry, kitchens, dinings, are nooks not considered as general lighting receptacles but special use receptacles. Everywhere else , not habitable areas, is considered to be continuous unless ruled by the "AUTHORITY HAVING JURISDICTION" is considered to be continuous.

The NEC says 100% of the non continuous and 80% of the continuous loads.

Hope this helps

Wg
 
  #9  
Old 01-17-01, 09:35 PM
Guest
Visiting Guest
Posts: n/a
Thanks Wg,

Your point is clear. And it was clear to me even before your last answer. I do appreciate your propensity for detail and clarity, and I understand the need for it. Rest very assured that I do indeed understand the difference between residential power needs verses non-residential needs. And if I did not understand it, you made the point crystal clear for everyone else reading this as well

In short, I'm on board with your meaning .

You are more exhaustive in explaination than anyone I can think of. That is a 'good thing'! That is why I proudly gave you the name of "professor" in another post. See
http://forum.doityourself.com/showth...threadid=46894 if you have not seen my comments.

Thanks for the feedback doc!
 
  #10  
Old 01-18-01, 09:03 PM
Guest
Visiting Guest
Posts: n/a
How much difference would it be if we install a 400w, 500w 0r even a 1000w lightbulb? size of wire..ect
 
  #11  
Old 01-19-01, 07:45 PM
Wgoodrich
Visiting Guest
Posts: n/a
A 20 amp circuit would be good for 2400 watts @ 100%.

Hope that helped

Wg
 
  #12  
Old 01-20-01, 09:06 PM
Guest
Visiting Guest
Posts: n/a
Thanks for all the relies!!

would you recommend some of the good books, that may help me out?
 
Reply

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


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: