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orange 02-19-2008 11:01 AM

Power to Switch First
 
I found this forum while searching for info on pot light install.
Saw response to someone by Stubbie on this subject. Could someone comment on the advantages/disadvantages of power to switch first?

In a remodel, I am adding 2 small pot lights to a mid circuit plug. The pot lights (50Watts) have thermal protection and very small box on top. It says it can take max. 2 12AWG IN and 2 12AWG Out. In my view you'd be hard pressed to put 2 #14 IN with wire nuts, so was looking at power to switch first.

Comments please.

orange

Stubbie 02-19-2008 12:06 PM

No better than the source to answer. I like power to a switch first for both 3 ways and single poles. This gets a neutral in that box vs. no neutral like a switch loop with power to the light fixture first. Many more options available down the round if changes are made.
As far as one being better than the other they both work and nothing wrong going either way. If only powering one light hitting the switch first will reduce the number of wires in wirenuts at the light fixture. And yes the manufacturers don't give you much room in some of the wiring enclosures. One cable in and one cable out is to allow for connecting to another light and switch loops to a single light.

arichard21 02-19-2008 12:12 PM

Quick question:

Do they make cables specificly for things like switch loops containing 2 black wires, as opposed to 1 BK 1 WH and coloring the white to identify it as HOT?

Stubbie 02-19-2008 12:37 PM

I made a reply then deleted I think the best approach here is to ask why do you think it would make a difference?

arichard21 02-19-2008 12:49 PM

Quote:

Originally Posted by Stubbie (Post 99345)
I made a reply then deleted I think the best approach here is to ask why do you think it would make a difference?


Just curiousity, I guess. I can see several instances that they could be used... switch loops, 240 volt applications, etc.

My thinking is that if a homeowner opens up a switch and sees a white wire with electrical tape or marker on it they aren't always going to know that the white wire is hot...

Stubbie 02-19-2008 01:16 PM

Ok thats fair enough. First the NEC and the manufacturers didn't design wiring for the homeowner. They did however expect who ever opens a switch box to understand what they would be looking at and how it is supposed to work. If you saw a white wire connected to a switch you know darn sure it is either hot or switched hot or it would not be landed on a switch. If it is marked black I know it is the constant or power hot. I know this because that is the correct convention. On a 3 way switch it can be a switched traveler as can black and red. If a black and red (we are considering nm-b) are landed on a single pole switch one will be switched hot (usually red) and one will be constant power....again by convention. True gounded legs (neutrals) are never switched in a premise wiring method, unless someone has done something real unorthodox.

AllanJ 02-19-2008 01:26 PM

Quote:

Originally Posted by arichard21 (Post 99337)
Do they make cables specificly for things like switch loops containing 2 black wires, as opposed to 1 BK 1 WH and coloring the white to identify it as HOT?

14-2 Romex type cable with red and black conductors is used in Canada. It's a low volume (manufactured wise) item and therefore costs a lot more per foot. It would not be universally adopted from this point forward unless the NEC were changed to forbid white-black cables in switch loops.

arichard21 02-19-2008 01:27 PM

Quote:

Originally Posted by Stubbie (Post 99354)
Ok thats fair enough. First the NEC and the manufacturers didn't design wiring for the homeowner. They did however expect who ever opens a switch box to understand what they would be looking at and how it is supposed to work. If you saw a white wire connected to a switch you know darn sure it is either hot or switched hot or it would not be landed on a switch. If it is marked black I know it is the constant or power hot. I know this because that is the correct convention. On a 3 way switch it can be a switched traveler as can black and red. The black or red (we are considering nm-b) will be the switched hot on a single pole switch....again by convention. True gounded legs (neutrals) are never switched in a premise wiring method, unless someone has done something real unorthodox.

Makes sense. Thanks.

orange 02-19-2008 03:10 PM

Quote:

Originally Posted by Stubbie (Post 99334)
No better than the source to answer. I like power to a switch first for both 3 ways and single poles. This gets a neutral in that box vs. no neutral like a switch loop with power to the light fixture first. Many more options available down the round if changes are made.
As far as one being better than the other they both work and nothing wrong going either way. If only powering one light hitting the switch first will reduce the number of wires in wirenuts at the light fixture. And yes the manufacturers don't give you much room in some of the wiring enclosures. One cable in and one cable out is to allow for connecting to another light and switch loops to a single light.

Thanks for the response. It's what I was thinking(hoping) but it's good to get confirmation from a tradesman.

Stubbie 02-19-2008 03:53 PM

It is also very common to run three wire cable from a single light fixture to the switch box. This will allow for replacement if a ceiling fan/light or some other light and motor operated appliance without rewiring. The red wire is just left unused until needed.

Silk 02-19-2008 11:35 PM

Just a side note. There have been NEC proposals to require a neutral at all switches for future "smart" devices which will consume power and not just switch it, and for that a neutral is required. The proposals have failed so far, but it is only a matter of time before it will be required.

220/221 02-20-2008 09:07 PM

Quote:

My thinking is that if a homeowner opens up a switch and sees a white wire with electrical tape or marker on it they aren't always going to know that the white wire is hot...

It's not called a suicide switch for nothin :thumbsup:

CowboyAndy 02-21-2008 06:55 AM

So, what is the general concensus... do the pros prefer to run power to the switch first or run on a switch loop?

HouseHelper 02-21-2008 09:20 AM

Quote:

Originally Posted by CowboyAndy (Post 99944)
So, what is the general concensus... do the pros prefer to run power to the switch first or run on a switch loop?

Switch first. The only exceptions I make are on remodels where going to the light first is more cost effective.

AllanJ 02-21-2008 09:40 AM

Quote:

Originally Posted by Stubbie (Post 99392)
It is also very common to run three wire cable from a single light fixture to the switch box. ... The red wire is just left unused until needed.

By the way, if power came to the fixture, would it be proper to leave the white wire unused for the future? Even though the usage first thought of was a second switch for a fan, etc. and the white wire would have to become the unswitched hot at said later date?


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