Using 14/2 for lights


  #1  
Old 08-03-08, 06:24 PM
S
Member
Thread Starter
Join Date: Nov 2005
Location: Illinois
Posts: 125
Upvotes: 0
Received 0 Upvotes on 0 Posts
Using 14/2 for lights

I have yet another question. I plan on bringing power into the switch box by 12/2, is it acceptable then to run 14/2 out of that switch box to the light?
 
  #2  
Old 08-03-08, 07:09 PM
C
Member
Join Date: Aug 2007
Posts: 114
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by scotty18
I have yet another question. I plan on bringing power into the switch box by 12/2, is it acceptable then to run 14/2 out of that switch box to the light?
Only if you change the breaker to 15 amp.
 
  #3  
Old 08-03-08, 07:24 PM
S
Member
Thread Starter
Join Date: Nov 2005
Location: Illinois
Posts: 125
Upvotes: 0
Received 0 Upvotes on 0 Posts
I don't entirely understand why the breaker should be changed. The short ends of wire from the light of something like 16 guage. Does that also mean that on a 20 amp breaker all switches and receptacles have to be rated for 20 amps?
 
  #4  
Old 08-03-08, 07:45 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,976
Received 194 Upvotes on 170 Posts
No the switches and receptacles do not need to be rated for 20 amps. Rarely will you ever try to control more than 15 amps of lighting from a single switch. As long as there is more than 1 physical spot to plug a cord in you can use 15 amp receptacles. A common duplex counts as 2 places to plug in.

Fixtures are listed with the smaller gauge leads and are to be used as listed. Even mutiple bulb fixtures will not be above the load that the smaller wires can handle. They also use a different insulation that can affect their ampacity.
 
  #5  
Old 08-03-08, 07:52 PM
S
Member
Thread Starter
Join Date: Nov 2005
Location: Illinois
Posts: 125
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the replies. I am still not exactly clear if I can use 14 guage wire from a switch to a light if the circuit has a 20 amp breaker. Is that a NEC violation?
 
  #6  
Old 08-03-08, 08:02 PM
W
Member
Join Date: Jul 2008
Location: Kingston, PA
Posts: 131
Upvotes: 0
Received 0 Upvotes on 0 Posts
No, you cannot. And yes, it is a violation.
 
  #7  
Old 08-03-08, 08:04 PM
D
Member
Join Date: Jul 2008
Location: USA
Posts: 339
Upvotes: 0
Received 0 Upvotes on 0 Posts
If you have 14 gage wire ANYWHERE in the circuit you need to protect with a 15A breaker. Either change the breaker or the wire size to the light.
 
  #8  
Old 08-03-08, 08:11 PM
S
Member
Thread Starter
Join Date: Nov 2005
Location: Illinois
Posts: 125
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sometimes it seems like codes don't make sense and this is one of them. I understand that 14 guage wire is rated at 15 amps and if it is protected by a 20 amp breaker, the wire could overheat in the event of a short. But how then can it be ok for the pigtail wires form the light fixture to be a smaller wire and how can it be ok to use a switch rated for 15 amps?
 
  #9  
Old 08-03-08, 08:32 PM
D
Member
Join Date: Jul 2008
Location: USA
Posts: 339
Upvotes: 0
Received 0 Upvotes on 0 Posts
You are right, at least on the surface at first glance many of the codes seem silly but they are well thought out and there to protect you.

In your example... The wires in the light are short and protected within a box. Likewise the switch is within a box. This give some added protection. The NM wire in the walls have no such protection and could overheat and fail if 14 gage cable was subjected to 20A vs 15A for a long period. Is it likely this would ever happen? Probably not but whenever you investigate a disaster it is often a series of things that lead up to a failure. One never knows what other things could happen so it is best to be on the safe side.
 
  #10  
Old 08-04-08, 06:42 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,976
Received 194 Upvotes on 170 Posts
Scotty,

Please reread post #4 above. Your questions were answered there.

If you have more questions just followup here.
 
  #11  
Old 08-04-08, 08:22 PM
R
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,070
Upvotes: 0
Received 1 Upvote on 1 Post
Scotty,
A direct short with 16-gauge wires will blow a 20-amp breaker almost instantly. The 16g wires won't have time to heat. A partial short or heavy power draw on those same wires could cause the wires to heat before the breaker trips. Fortunately it's very difficult to overload a single lighting fixture. The 16-gauge wires can easily handle the load, even if all the bulbs in a 6-lamp chandelier were replaced with 100 watters.

RE the code challenges: What if the next homeowner decides to add a high-draw device in place of the light? Say, a heater/fan in a bathroom or 20 more feet of 12/2 off the light for an air conditioner? Suddenly your 14/2 is seriously overloaded. The breaker is rated for 20 amps, the 14/2 is rated for 15, and the devices are pulling 17.

The common household switch is rated at 15, but it's not a circuit breaker. It won't kick off if it has to pass 17 amps, or even 20. It could heat up, though, or more commonly it will arc when turned on or off. Code in this case seems stupid, but it also takes into consideration the fact that there will usually be more than one 15a-rated switch on any given 20a circuit.

For a graphic illustration of one possible outcome, please take a look at this thread.
 

Last edited by Rick Johnston; 08-05-08 at 05:13 AM.
  #12  
Old 08-05-08, 07:40 AM
T
Member
Join Date: Oct 2005
Location: USA
Posts: 1,569
Received 74 Upvotes on 69 Posts
pcboss has it correct

but, to make this even easier:
house wire is made to be attached to flammable material ie 2x4's

internal luminere wiring is not...
 
 

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