Wiring 3 way switches for detatched garage lights

[beerguzzler50]

Thanks for the correction. I guess I'm a little confused. What are the issues is I use #14 ground to the garage vs. #14 ground to the house?

[Thomas D. Horne, FF EMT]

When you run a separate EGC to the garage it will be in parallel with the neutral of the feeder because the code requires it to be bonded to the neutral at both buildings disconnecting means. That means it will carry a portion of the neutral current during normal operating conditions. If anything then happened to the continuity of the feeder neutral the EGC will carry the neutral current at a very high voltage drop until it fails open. With either a high voltage drop or an open circuit the voltage of all exposed metallic portions of the electrical system and any conductive surface in contact with it will rise to 120 volts relative to the earth or such grounded conductive surfaces as the garage floor.

I am a firefighter / EMT and I have run a call were such a condition killed the user. Yes it's rare but it does happen. Since such incidents are rarely investigated when they occur in a non work setting the number of such incidents is undoubtedly higher than is currently known.

[Tom Horne, Electrician]

Yes that is exactly the type of parallel pathway that the code forbids for three wire feeders. Your switching circuits do count as another metallic pathway.

If you run all portions of the garage end of the circuit in non metallic raceway, use all nonmetallic boxes and cover plates, and install only non metallic lighting fixtures it might be reasonably safe. The moment one of the non metallic switch plates or fixtures is replaced with one that has exposed metal then your single layer of safety is gone. You would also have to violate the code requirement that the EGCs in the garage should be bonded to the neutral of the feeder at the building disconnecting means.

You can use X10 controls via the feeder without violating the code. Wireless three way switches that use radio signals to control the switch at the light would also work.

[mm]

You do? Why7 IIUC, you don't want 3 pairs of 3-ways, you just want three switches to control some lights in the garage.

I presume you want one switch in the house and one in the garage. Where do you want the third switch?

It doesn't really matter.

When you go above two 3-way swtiches, the rest of them have to be

4-way switches. Electrically, the 4-ways have to all be between the three-ways that are at the end.

Between each pair of switches you need 2 hot wires, only one of which will be hot at any given moment. Plus a neutral wire. Plua the uninsulated ground that comes inside BX, for example.

Yes.

I don'tt know what you mean "per switch". You need 4 wires AT each switch, but in most ways of looking at things, they are the same 4 wires. Two are the neutral and ground -- two wires come in and two wires go out, usually spliced witha wire nut.

In addition, for the first 3-way switch one wire goes in and two go out. For the second 3-way, two wires go in and one wire goes out. And for all the 4-ways in between, 2 wires go in and 2 wires go out.

This may sound like 8 wires, but 4 are going back to the previous switch and 4 are going on to the next switch.. You only need four wires, and some places only 3.

No relays, no X-10 needed imo.

Remove NOPSAM to email me. Please let me know if you have posted also.

[Mark Lloyd]

X10 devices use a 121KHz signal sent over the power line. A burst is sent at each zero-crossing (so obviously, X10 requires AC power). No additional wiring is required. X10 commands are slow, about 1/3 second per command. A simple operation usually takes 2 commands. one to select the device and the other to operate the selected device.

One good thing about X10, is that it uses separate ON and OFF commands (rather than just a toggle). This is useful (or even essential) sometimes.

Wireless X10 controllers exist (with the decreased reliability of wireless). It's best to avoid them if you have (or can add) wires to the control locations (the simplest and least expensive X10 controller is an 8-device unit that can be plugged into any outlet using the same power transformer as the devices to be controlled).

Note that there will be a unit code (1-16) and house code (A-P) allowing up to 256 addressable devices. The controller can only be set to one house code (it's best to avoid A since that's the default). You could use G1, G2, G3, and G4.

[Dennis]

I could be mistaken, but you mentioned the ground wire should be white?

The "grounded" conductor (mistakeningly called a neutral in a 120 volt circuit) is colored white, the "grounding" (or bonding) conductor is green.

[Bud--]

I'm not sure what you are asking. You can't run a #14 ground from house to garage as this would be a "separate metalic path" which is prohibited if you run only a neutral (without a ground) as the supply in your feeder. A #14 ground from house to garage would appear in parallel with the neutral. The grounds at the garage are picked up from the common neutral/grounding-electrode.

bud--

[Bud--]

You ran a feeder with 2 hots, a neutral and no ground. The other option is to run include a ground. The ground wire is sized from a table and would likely be smaller than #2, I'm too lazy to look it up. The ground wire from the house is connected to the ground wires in the garage (ground bar) and the grounding electrode (usually ground rod). The difference is that the neutral bar is isolated from the garage ground system. If you wired the garage this way you don't need #14 grounds from the house to the garage because the feeder ground is sufficient.

I have a very rare disagreement with Tom Horne, who puts up very good posts. The fault clearing path as you are wiring the garage is via the feeder neutral. If you ran a separate ground wire with the feeder, the fault clearing path would be through the likely smaller feeder ground wire. I don't see how that is an advantage.

I assume there is only one Tom Horne and you just changed hats?

bud--

[beerguzzler50]

OK, let me restate, cause I think I am finally getting it.

for my light fixture in the garage, the neutral (white wire) stays in the garage. It is the Hot/Switched Hot/Runner (3 wires) that goes to the House 3way and then to the garage 3way. I got that.

If I run a #14green wire from the garage to the house as an EGC ground (just for the switch which is in non-metalic switchbox)...I have violated code?

If I run the green ground wire from the house side switch to the house EGC, and keep the garage side switch grounded to the garage, would this allow me to keep the grounds separate and not violate code/be unsafe?

I'm trying to figure out my options short of running another #4AL feeder cable for the ground. I can pull more #14 wires, but just need to know how I can make this code compliant and safe.

Thanks!

[Goedjn]

I don't think you can. You have two mutually exclusive choices:

1: Supply power to the garage with two hot wires, and a combined ground/nuetral connected to earth in the garage.

and

2: Have switches in the house that are electrically connected to something in the garage.

I'm pretty sure you're not allowed to do both. SO you have to either figure out how to control the garage lights with a remote, or run a 4-wire feeder cable to the garage, and abandon the local ground.

[beerguzzler50]

I don't have the NEC, but my understanding is that 225.30(d) allows an exception for outside lighting to be controlled from multiple locations is permitted. I'm not clear though if what I want to do falls within that. Either way since it is detached, I must have the local ground even with a 4 wire feeder, just would keep the neutral and EGC seperate in that case. (i think)

[Thomas D. Horne, FF EMT]

No you do not "abandon the local ground"! The grounding electrode system is required in either case whether the feeder has an Equipment Grounding Conductor (EGC) run with it or not. In a three wire feeder the neutral of the feeder is bonded to the grounding electrode system of the garage at the building disconnecting means. With a four wire feeder that includes an EGC The EGC is bonded to the grounding electrode system at the building disconnecting means and the neutral is kept aloof from ground in the garage so that the neutral current will not flow on the parallel conductive pathways to the building in which the service is located.

[Tom Horne, Electrician]

Perhaps I was not clear. If the fault clearing path is via the feeder's neutral it would be because the Equipment Grounding Conductors (EGCs) are connected to the main bonding jumper at both buildings. Between the main bonding jumper and the switch boxes the EGC would not be in the same raceway or cable as the current carrying conductors for the circuit. Such divergent pathways always have a higher impedance then one that remains with the current carrying conductors for it's entire length.

[Bud--]

Assuming lites are on the same circuit you can run a common hot plus 2 switch legs per switch.

With your configuration - feeder with no house-ground wire - a #14 house-garage ground wire is a prohibited separate metalic path.

Sounds good to me.

[Dennis]

This is a feeder, you cannot go to earth ground on the load side of a service (NEVER). By code, he must run a 4-wire feeder to the remote panel.

[Bud--]

Read 2005NEC 250.32 (B) (2)

bud--

[Dennis]

Well I be damned. They changed it to allow feeders. I was wrong, and not more than a little surprised. Haven't had many states reference 2005 yet, most are still on the 99 where it was referencing services. (After all these years of it being a no, no...... grin.)

Thanks for the reference Bud.

Dennis