The first thing we need to know is the size of the box. That will tell us whether it has enough space for the additional conductors you would have to add to have a second switch and a new cable in that box. Don't get too worried if it is not large enough because there are other ways to accomplish what you want to do which we will explain separately.I tested both switches and they both have power to them when off.
Why do you say that testing between the hot and the ground will not identify the always hot wire?The first thing we need to know is the size of the box. That will tell us whether it has enough space for the additional conductors you would have to add to have a second switch and a new cable in that box. Don't get too worried if it is not large enough because there are other ways to accomplish what you want to do which we will explain separately.
If you turn the circuit off, and extend all of the wires out of the box, you could then take photographs that show how all the wires are connected and what color they are. If the wires are cloth or fiber covered do not manipulate them at all and let us know. Then post the photographs in a new posting. You needn't remove the switch from the wires or open any splices to take the photographs since the way the wires are connected to the switch and to each other will tell us things we need to know to be of help to you. Be gentle with the wires and avoid creating sharp bends in them.
Tell us if there are wires from one cable or two connected to the 3 way switch in the device box which you are interested in, The biggest clue here will be a white wire, which may have been marked or tagged to indicate that it is not a Grounded Current Carrying Conductor, connected to the 3 way switch and that wire comes from the same cable as the other 2 wires that are attached to the switch. If there is only one cable connected to the switch and no other cables in that box you will have to run another source of power to that box in order to supply a new set of lights from a switch that will be mounted in that same box.
If there are 2 cables in the box, were you would like to take power from, and a splice which connects white wires together then here is the test procedure:
De-energize the circuit and test all of the conductors in that box with a non contact voltage probe.
If that test does not indicate any wire being energized then test all of the wires connected to the 3 way switch to the bare ground wires in the box using a contact tester.
If there is no voltage present remove the switch from the box and let it hang by it's wires. Do not disconnect any wires from anything! Do not open any splice!
In order to be able to connect the tester probe to the white wire, without breaking the splice, gently roll the wire nut so that it's tip points into the box.
Since there are now energized terminal screws and wires in the box you must have guarded those exposed energized conductors against contact by anyone.
Re-energize the circuit.
The common terminal of the switch is the one which is a different color from the other 2 terminals.
Test between the common terminal screw of the 3way switch and the white wire when the light is off. To make contact with the white wire you will insert one of the testers probes into the wire end of the wire nut which you turned around prior to re-energizing the circuit. Do not test to the bare or green wire because that will not tell you what you need to know. If the common terminal is still energized when the light it controls is off then it is at the end were the power comes from and will remain energized at all times. The wire which is connected to that common terminal is the wire that you can take power from.
If that common terminal is deenergized when the light is off then it is at the switched end of the three way circuit and cannot be used as a source of power for anything else.
Did I say that? I didn't mean to! I said that using the Equipment Grounding Conductor (EGC) "will not tell you what you need to know." He will need both conductors of a cable that is energized all the time in that box in order to use that cable for a source of power for a new circuit. By testing between the common conductor at the 3 way switch and the white wires in a splice he will be sure that he has both an energized conductor and a Grounded Current Carrying Conductor in that box. I don't yet know if there are other circuits in that box. If there are other circuits in that box spliced white wires might be a traveler junction for a different 3 way circuit which passes through that box but is not switched at that location. Que the old Shadow radio show intro. Who knows what evil lurks in the heart of a now retired electrician? Not even the shadow knows! We have no easy way of knowing about how this box was originally wired or what may have been done since then. And he allowed as he was just making sure. Arlo Guthrie in the movie Alice's Restaurant.Why do you say that testing between the hot and the ground will not identify the always hot wire?
I would prefer that he test between the hot and the ground rather than trying to get a probe inside the wire nut connecting the neutrals.
Here are the two options.
Yes there would be an always hot at one switch. However there might not be a neutral at either switch.
It is required as of the 2014 code - NEC 404.2(c). There must be a grounded circuit conductor (neutral) in all switch boxes, although there are some exceptions. Here are a couple illustrations, showing where the 4-conductor cable would be used for dead-end switches:Just for my education, I have never seen 4 wire used to make a three way switch work. I always seen and used 3 wire 14 ga. or 12 ga. wire to make them work. Never seen the white neutral run through and capped off with a wire nut. Is this required by code or just an illustration to account for all the wires? I realize that means you have to use the white wire as one of the travelers.
First lets lay out the 2 basic pathway types for any switch. One is the switched feed. A pair of current carrying conductors; 1 grounded and the other energized come to the switch location and then continue on the load such as a luminaire. The energized conductor of a switched feed goes through the switch to provide control. In all other respects the box in which the switch is mounted is much like a splice box with the Grounded Current Carrying Conductor (Neutral) spliced through the box with a wire nut and the Energized Current Carrying Conductor connected through a switch instead of a wire nut.