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Subject - 3 way switches
doogie my sister inlaw house has three way switched that dont work properley.
they didn't use three wire when they put it in they just used two with no ground how do you hook up a three way switch that is wired with two wires coming in two the box?
Scott Vickrey You can't you need three wires and you should always have a ground so that makes 4 wires total.
doogie so i guess i have to run a three wire to it correct
JimmyDee
quote:
Originally posted by doogie

so i guess i have to run a three wire to it correct


Yep.
Jim
zapped208 Scott V,- Great diagram........It even works!
JimmyDee When I taught this concept, I came up with 3 rules to hooking up 3 way switches:
(1) The white or neutral goes from the feed directly to the load. (in this case it is the light)
(2) The dark screw on one of the 3 way switches goes directly to the feed.
(3) The dark screw on the other 3 way switches goes directly to the load.

This will not change for any reason and of course, the remaining screws connect to the travelers.
Jim
lctrc789 Years ago I worked for a residential contractor and it seems they never bough three wire not even for three way switches, so we used to do simlpe three way hook ups. Hot feed and neutral to switch one, then pull a two wire between the 3 way switches for travelers then two wire to the light as a switch leg. Thus you have a two wire traveler.two wire hot feed at switch one and a two wire feed at switch two. with grounds.
I have seen this done and it can be confusing to those who use three wire all the time.
JimmyDee
quote:
Originally posted by lctrc789

Years ago I worked for a residential contractor and it seems they never bough three wire not even for three way switches, so we used to do simple three way hook ups. Hot feed and neutral to switch one, then pull a two wire between the 3 way switches for travelers then two wire to the light as a switch leg. Thus you have a two wire traveler.two wire hot feed at switch one and a two wire feed at switch two. with grounds.
I have seen this done and it can be confusing to those who use three wire all the time.

Don't think this is legal because the neutral has to be run with the travelers. Problems with induction can come out of a wire run with out the return paired up with it. Using metal boxes would cause warm spots where the wire goes into the box. Might not be a major danger because of the lower amperage but is not good.
Jim
lctrc789 Jimmy I don't think we ever had a problem with these set ups and the did pass inspection, The two wire traveler was just that a two wire traveler. the hot feed was 2 wire and the switch leg was two wire as well all with grounds.
It is not an issue of the fields counteracting here in romex.
lctrc789 Actually Jimmy, I think this does meet code requirements. Article 380-2 states that the ungrounded conductor be used for switching (it does that) and that switch loops do not require grounding. Also if you read article 200-7 c(2) it may help you to understand more on the 3 and 4 way system. Using romex.
Ryan_J Ditto Pat. The nuetral does not have to be run with the ungrounded conductors for a three way, but I think it should be.
JimmyDee
quote:
Originally posted by lctrc789

Actually Jimmy, I think this does meet code requirements. Article 380-2 states that the ungrounded conductor be used for switching (it does that) and that switch loops do not require grounding. Also if you read article 200-7 c(2) it may help you to understand more on the 3 and 4 way system. Using romex.

quote:
207-7c(2) Where a cable assembly contains an insulated conductor for single-pole, 3-way or 4-way switch loops and the conductor with white or gray insulation or a marking of three continuous white stripes is used for the supply to the switch but not as a return conductor from the switch to the switched outlet. In these applications, the conductor with white or gray insulation or with three continuous white stripes shall be permanently reidentified to indicate its use by painting or other effective means at its terminations and at each location where the conductor is visible and accessible.


This is not what I was talking about. I was referring to a conductor being run without its return conductor in the same cable package not the color of wire used.


Artical 380.2??? is this 2002 NEC?
This deals with the neutral conductor being used as a switch leg and not the subject I was talking about either.
Jim
JimmyDee This is more of what I had in mind and what I was talking about and the system that is being talked about. Sure seems to be violating this article.
quote:
300.20 Induced Currents in Metal Enclosures or Metal Raceways.
(A) Conductors Grouped Together. Where conductors carrying alternating current are installed in metal enclosures or metal raceways, they shall be arranged so as to avoid heating the surrounding metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.
Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C).
Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 426.42 and 427.47.
(B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.


If one were using metal boxes, wouldn't this apply? If one were to look closely at the proposed circuit, they would find this condition caused by the travelers, only one of which is energized a any given time, together in a cable with no return path. In this case a neutral. This will cause the problem addressed in the previous code passage where it leaves one switch box and enters the other.
Jim
Ryan_J Hi Jimmy. I agree with you if metal boxes are used. Sorry, I should have indicated that. I was thinking of residential, which, in my area, I never see metal boxes. In addition to 300.20, see 300.3
lctrc789 I could see this if it were if conduit and the counter emf would be a problem but not in romex. The box size should be able to handle it anyway shouldn't it.
Most residential applications are plastic or fiberglass boxes and have very little cuurnet for a light or 2.
You are not talking a commercial job here where you may have many amps of current in one conduit or gang box with several switches and circuits.
JimmyDee I've seen a few in the past few years that used metal boxes. Probably no contractors. I've also seen where they have been used for stacking when they don't have the right size or # of gangs needed.
Jim
JimmyDee
quote:
The box size should be able to handle it anyway shouldn't it.

Size doesn't have anything to do with it. It is what the box is made of that is the problem. I realize that this is not the discussion but was told somewhere is that if one phase goes through a single hole in a steel box and amperage is 50 amps, it will damage the wire because of heat caused by induction. I think this is what is called a burning ring of fire.
Jim