3-way switch loops

[iwire]

Re: 3-way switch loops

Guys I am not sure we will get an answer to this one.

I tried Yahoo and Google and it seems it is a well known quote thats source is unknown.

I saw it credited to Abe Lincoln also.

 

[peter d]

Re: 3-way switch loops

Originally posted by georgestolz:

That's why I said to switch and feed opposite ends. I hate stocking an odd oversized box in my truck to cope with an inability to count.

 

[iwire]

Re: 3-way switch loops

Originally posted by georgestolz:
Three cables? Let's try the same setup, without switching and feeding at opposite ends.

Cable 1: 14/3 Travellers for light kit
Cable 2: 14/3 Travellers for fan
Cable 3: 14/3 Travellers for half-hot
...Half hot, this will have to be a dead-end anyway...

Cable 4: 14/3 Switchleg for half hot
Cable 5: 14/3 Switchleg for C/F
Cable 6: 14/2 Power In
Cable 7: 14/2 Power Out

That's 19 CCC's.
19x2 = 38
+ Grounding = 40
+ Devices = 52
+ Clamps = 54

That's alotta wire, there.
That's why I said to switch and feed opposite ends. I hate stocking an odd oversized box in my truck to cope with an inability to count.

You sure lost me on this one.

1)Current carrying conductors do not apply to box sizing.

2)If your using plastic boxes there should be no 'clamp' count.

3)Why '2' grounds?

4)12 devices in a 3 gang?

 

[iwire]

Re: 3-way switch loops

Originally posted by peter d:
Personally, I always use deep boxes no matter what. It makes my life easier when it's time to put the devices in, and I never have to worry about a box fill problem.

That is also what the policy of the company I work for is.

99% of the time we will use 4" sq. deeps with plaster rings. No worries about box fill or trouble with large devices.

 

[peter d]

Re: 3-way switch loops

Originally posted by iwire:
2)If your using plastic boxes there should be no 'clamp' count.

Bob, since nonmetallic boxes larger than single gang are required to have clamps, whether integral or separate, I can see no reason why we can exclude them from our box fill calculations.

According to the Carlon website, when UL tests box volume, they break out the integral clamps.

 

[iwire]

Re: 3-way switch loops

Originally posted by peter d:
Bob, since nonmetallic boxes larger than single gang are required to have clamps, whether integral or separate, I can see no reason why we can exclude them from our box fill calculations.

314.16(B)(2) Clamp Fill. Where one or more internal cable clamps, whether factory or field supplied, are present in the box, a single volume allowance in accordance with Table 314.16(B) shall be made based on the largest conductor present in the box. No allowance shall be required for a cable connector with its clamping mechanism outside the box.

I do not consider the plastic 'flap' that poses as a clamp to be internal. It is part of the box wall.

An internal clamp IMO is what you find in a metal box with the screw.

 

[peter d]

Re: 3-way switch loops

Originally posted by iwire:
I do not consider the plastic 'flap' that poses as a clamp to be internal. It is part of the box wall.

An internal clamp IMO is what you find in a metal box with the screw.

The brown bakelite boxes that are so common in New England do require an internal metal clamp. There is no doubt this counts toward box fill.

As far as the PVC boxes go, they are all different. Some have very intrusive clamps that bend down and into the box when a cable is inserted, while others are indeed as you say, part of the box wall and take up very little room. I still count the clamps nonetheless.

 

[al hildenbrand]

Re: 3-way switch loops

1)Current carrying conductors do not apply to box sizing.

Well, that's one way to think of how to differentiate EGCs from the insulated conductors in the NMB cables.

2)If your using plastic boxes there should be no 'clamp' count.

A significant percentage of NM boxes have internal clamps (screw & bracket, or seperate bracket pinched in place)

3)Why '2' grounds?

That's 2 cubic inches for 1 ground

4)12 devices in a 3 gang?

And that's 12 cubic inches for three devices.

 

[iwire]

Re: 3-way switch loops

Originally posted by peter d:
The brown bakelite boxes that are so common in New England do require an internal metal clamp. There is no doubt this counts toward box fill.

Agreed

Originally posted by peter d:
As far as the PVC boxes go, they are all different. Some have very intrusive clamps that bend down and into the box when a cable is inserted, while others are indeed as you say, part of the box wall and take up very little room.

I have never seen a PVC box that has internal clamps, yes they fold into the box but they are not internal clamps IMO.

Count them if you want I would not.

 

[iwire]

Re: 3-way switch loops

Originally posted by al hildenbrand:

1)Current carrying conductors do not apply to box sizing.

Well, that's one way to think of how to differentiate EGCs from the insulated conductors in the NMB cables.

I would say that would be a bad way to do it as someone you teach that way may think neutrals do not count.

Originally posted by al hildenbrand:

2)If your using plastic boxes there should be no 'clamp' count.

A significant percentage of NM boxes have internal clamps (screw & bracket, or seperate bracket pinched in place)

See my answer above about this to Peter.

Originally posted by al hildenbrand:

3)Why '2' grounds?

That's 2 cubic inches for 1 ground

4)12 devices in a 3 gang?

And that's 12 cubic inches for three devices.

Yeah, I misunderstood his list.

[ July 10, 2005, 11:51 AM: Message edited by: iwire ]

 

[al hildenbrand]

Re: 3-way switch loops

Posted by IWire

someone you teach that way may think neutrals do not count.

Neutrals don't carry current?

I don't know Bob, I've seen this part of the Box Calc bring on a teachable moment in the eyes of the newbies as they struggle with current vs. voltage. . . I think one can argue just as well that "current carrying conductor" is a valuable tool in the continuum of learning about this Code.

 

[al hildenbrand]

Re: 3-way switch loops

Behold, one manufacturer's 3 gang NM wall case. It comes with factory installed internal clamps.

 

[iwire]

Re: 3-way switch loops

Originally posted by al hildenbrand:

Posted by IWire

someone you teach that way may think neutrals do not count.

Neutrals don't carry current?

I don't know Bob, I've seen this part of the Box Calc bring on a teachable moment in the eyes of the newbies as they struggle with current vs. voltage. . . I think one can argue just as well that "current carrying conductor" is a valuable tool in the continuum of learning about this Code.

Well we disagree here and I think you enjoy causing confusion. :roll:

If you want to turn 'current carrying conductor' into another 'outlet thread' I will step out the door now as I find those arguments counter productive and confusing to people just entering the trade. :roll:

JMO, Bob

 

[George Stolz]

Re: 3-way switch loops

Originally posted by iwire:
I have never seen a PVC box that has internal clamps, yes they fold into the box but they are not internal clamps IMO.

Count them if you want I would not.

Peter D wrote:
For a grand total of 30 cubic inches. Within the limits of most plastic 2-gang nail ons, so no box fill issues here.

My point is, I like Matt's diagram, and that is a very feasible way of doing it.

What kind of fan boxes do you use? Farmer-switching a ceiling fan is like trying to swallow a 2x4! A two-wire and a threewire in a ceiling fan box? Good luck!

Personally, I always use deep boxes no matter what. It makes my life easier when it's time to put the devices in, and I never have to worry about a box fill problem.

I just hate the Carlon boxes. We used them for a while, and went back to the Allied's. That stupid cable clamp in the back just bugs me.

How did the switched duplex enter the equation? Looks like you tried to stealth that one in.

It did sneak that in, but I feel it's a valid concern. Frequently, at least around here, bedrooms with ceiling fans are complimented by a switched outlet by the bed, even in the tract homes. So, I slipped that in for good measure.

In reality, it's balancing itself out--you're getting three switches, three gang box, just putting up higher numbers. But I'm reasonably sure the 4-gangs I use have only 54 cu in. I think my three-gangs weigh in at 46, or thereabouts.

So having 54 cu in of conductor fill in a 46 cu in box is like pounding 10 lbs of...sugar...in a 5 lb sack.

Edit: Changed "have" to "hate"
Amazing how a typo can change the meaning of a statement! (Imagine a smiley here, I already have 8!)

[ July 10, 2005, 12:22 PM: Message edited by: georgestolz ]

 

[iwire]

Re: 3-way switch loops

Originally posted by al hildenbrand:
Behold, one manufacturer's 3 gang NM wall case. It comes with factory installed internal clamps.

Yes and if it has those internal clamps I would count them.

If it has the typical fold in clamps I would not count them.

It's pretty straight forward.

 

[iwire]

Re: 3-way switch loops

Originally posted by georgestolz:

Originally posted by iwire:
I have never seen a PVC box that has internal clamps, yes they fold into the box but they are not internal clamps IMO.

Count them if you want I would not.

Bob, these are integral cable clamps. They have to be, to comply with 314.17(C).

I do not see where you get that idea.

The section requires securing to the box period.

That could be inside or outside with a separate NM connector.

Edit, By the way 'internal' is not the same as 'integral'

[ July 10, 2005, 12:25 PM: Message edited by: iwire ]

 

[peter d]

Re: 3-way switch loops

What kind of fan boxes do you use? Farmer-switching a ceiling fan is like trying to swallow a 2x4! A two-wire and a threewire in a ceiling fan box? Good luck!

 

[al hildenbrand]

Re: 3-way switch loops

Posted by IWire
It's pretty straight forward.

Yup, if there are internal clamps, count'em. Just as you chose to say don't count'em:

I have never seen a PVC box that has internal clamps,

I thought I'd attempt to add a little more information to the thread. . .

Also, Bob, you didn't answer the question I returned to you. . .What about neutrals as current carrying conductors?. . .

 

[peter d]

Re: 3-way switch loops

Originally posted by al hildenbrand:
Also, Bob, you didn't answer the question I returned to you. . .What about neutrals as current carrying conductors?. . .

The simple, non 500-post-thread answer is, "Yes, they are current carrying"

[ July 10, 2005, 12:36 PM: Message edited by: peter d ]

 

[George Stolz]

Re: 3-way switch loops

Originally posted by iwire:
The section requires securing to the box period.

That could be inside or outside with a separate NM connector.

Uh, in the blue Carlon boxes, how is NM secured to the box, if not by the crappy flappy things in the box?

How do you secure NM to Carlon boxes?
How do you secure NM to Allied boxes?

Why do the single gangs in both Carlons and Allieds differ from their multigang brothers?

I'd say, 314.17(C).

Peter: Good point. I use different ones. Had that coming.

[ July 10, 2005, 12:45 PM: Message edited by: georgestolz ]