three and four way swithes

[iceman77]

I've always pulled 12-2 for my travlers and 12-2 or 12-3 if I need constant hot for battery backup for my lights. my question is. Is it true I have to run my neutral or sw.leg with my travlers, if so why and where is it in the code because every body tells me I'm wrong but can't show me in code book 2002

 

[peter d]

Assuming NM cable and NM boxes you can do this by the NEC. And you have to make sure the neutral that you inevitably have to borrow with this scheme is from the same circuit that the hot is from, or else you will have an NEC violation.

That said, I consider this to be poor practice and it does cause issues with EMF.

 

[iwire]

I've always pulled 12-2 for my travelers and

If your using metallic wiring methods like MC I don't see anyway to wire three and four ways with 2 wire and meet the NEC requirements found in 300.3(B).

You have to run 3 wire, either using two for travelers and one for the neutral OR using two for travelers and one for the return to the fixture.

It is possible use all two wire NM cable and care to meet 300.20.

 

[peter d]

If your using metallic wiring methods like MC I don't see anyway to wire three and four ways with 2 wire and meet the NEC requirements found in 300.3(B).

You have to run 3 wire, either using two for travelers and one for the neutral OR using two for travelers and one for the return to the fixture.

It is possible use all two wire NM cable and care to meet 300.20.

Copy cat. :roll:

 

[crossman]

If your using metallic wiring methods like MC I don't see anyway to wire three and four ways with 2 wire and meet the NEC requirements found in 300.3(B).

You have to run 3 wire, either using two for travelers and one for the neutral OR using two for travelers and one for the return to the fixture.

It is possible use all two wire NM cable and care to meet 300.20.

Hmmm..... but the two travelers in one cable and the rest in a second cable is not going to meet 300.3(B). Now, trust me, there are places in my own house where I used 2 - 2 conductors in place of 1 - 3 conductor , but it is a violation in my opinion.

Got any diagrams where the travelers could legally be in a 2-wire?

 

[iwire]

300.3(B).

300.3(B)(3) Nonferrous wiring methods

 

[crossman]

Well holy Cow and Doh! How come that never made an impression on me before? Thanks Bob.

BTW, when we were discussing branch circuits sharing a common neutral a few days ago, i tried to find the section about column-width panelboards which allows the neutrals to originate in the pullbox.... in other words, a common neutral goes to a neutral bar in the pullbox. Well, there it is, 300.3(B)(4)

 

[iwire]

I learned of that section on the forums as well.

 

[quogueelectric]

Well holy Cow and Doh! How come that never made an impression on me before? Thanks Bob.

BTW, when we were discussing branch circuits sharing a common neutral a few days ago, i tried to find the section about column-width panelboards which allows the neutrals to originate in the pullbox.... in other words, a common neutral goes to a neutral bar in the pullbox. Well, there it is, 300.3(B)(4)

I cant believe my eyes at the picture in the handbook as it apears to show all of the pipes drilled through the flange in the I column. I cant imagine any structural engineer aproving this without reinforcing the steel. But I have never seen one of these panels I am curious to know why they exist (safe from a forklift I presume)and I would think they would be top fed for the most part.

 

[al hildenbrand]

Got any diagrams where the travelers could legally be in a 2-wire?

I'll do you one better than travellers in a 2-wire.

Consider:

 

[iwire]

Al with both switches 'down' you have a 310.4 issue IMO

 

[dicklaxt]

Bob,whats the issue with both down?.I don't have a book handy? BTW,Al, interesting 3-way setup,how would you hang a 4-way in to that arrangement?.

dick

 

[iwire]

310.4 prevents conductors smaller then 1/0 to be run in parallel except under some specific conditions.

It is my opinion that Al's clever method does not fit the specific conditions that 12 or 14 AWG can be run in parallel.

I want to be clear and say I do not see a safety issue, just a code issue. :smile:

 

[iwire]

I also just noticed another issue.

Al's sketch shows the hot and neutral continuing on presumably to other loads.

The loads down the line will be supplied from a grounded conductor in one cable and a ungrounded conductor in another cable. This would bring us back to a 300.3(B) violation for the loads down line.

Also place the left switch down and the right switch up and follow the current flow. With the switches in that position the left cable will only be carrying grounded current and the right cable only ungrounded current.

 

[dicklaxt]

Okay that being said, if the thinking is that parallel means something other than wires sharing a load equally.

Here is another example thats fits physically to the schematic/wiring diagram. If I were to pipe this up using all 1/C's,would there be a problem with any code violation?This of course is a bit of a different question than the OP.

Al, hanging a 4 way between the hot feed thru and the common/common of the 2-3 should work.

dick

 

[al hildenbrand]

Al with both switches 'down' you have a 310.4 issue IMO

I know this has been hashed thru on the Forum before. I agree that it is not a safety issue, with respect to inductive heating when a nonmetallic method is used (EMF is another matter, but that's not in the Code yet).

The conditions (a), (b) and (c) to Exception No. 1 under 310.4(A) are all met by the circuit in my sketch above. The technical Code issue is in the shopping list of installations of small gage paralleled conductors given in the first paragraph of Exception No. 1. "Control power" is hard to stretch to fit my sketch.

However, I submit, the Code issue is the imprecise meaning of "parallel" in the context of 310.4.

My sketch illustrates a hot conductor paralleled with the common-common conductor, in one of four switch states, but the paralleling is not for voltage drop improvement or reduction of conductor size. So, I would say, 310.4 doesn't apply.

If the meaning of "parallel" in 310.4 were a blanket meaning covering all possible parallel installations, then installing metal raceway between a meter socket and the service disconnect would be a violation.

 

[al hildenbrand]

hanging a 4 way between the hot feed thru and the common/common of the 2-3 should work.

One can add one, or more, 4 ways to this, but:

1. none of the 4 ways can break the common-common conductor,
2. nor can they break the hot conductor.

Also, I haven't been able to imagine a way to introduce 4 ways that can be accomplished solely with 14/2 (unless there are abondoned conductors). The minimum I've achieved has been with a some 14/3.

 

[al hildenbrand]

If I were to pipe this up using all 1/C's, . . .

What kind(s) of pipe?

 

[dicklaxt]

Al why can't the 4-way break the common-common conductor? When I speak of pipe I'm saying any RMC.

If I call the 3-way a SPDT switch and the 4-way a DPDT switch and use all 1/C wires routed in RMC as required, then my network becomes a hot ,neutral, control wires(switch legs) and switches that can control anything desired,I don't see an issue electrically with any of the above,,,,whats your take on this scenario and how would it be concerned with a so called common-common?I would call this just another control wire that runs from A to B.

dick

 

[iwire]

My sketch illustrates a hot conductor paralleled with the common-common conductor, in one of four switch states, but the paralleling is not for voltage drop improvement or reduction of conductor size. So, I would say, 310.4 doesn't apply.

I don't see any code section supporting the view that if paralleling simply happens by consequence that is OK.

If the meaning of "parallel" in 310.4 were a blanket meaning covering all possible parallel installations, then installing metal raceway between a meter socket and the service disconnect would be a violation.

IMO the 310.4 does not apply to grounding conductors or raceways, but I know the RMC would actually be both grounded and grounding.

No comment on the 300.3(B) issues I brought up?