First question here. Hope I get the terminology correct.
We have a three switch panel in our living room. Position 1 is a 3-way switch that toggles lights on the underside of a covered patio. Power is supplied by a circuit that controls the patio and a small nook off our kitchen. The other 3-way switch is about 40 feet away in a bedroom off the kitchen. We have never known what the switches at position 2 and 3 do, for years.
Clearing away some foliage in preparation for house painting, we discover an outdoor box with a screw in flood light receptacle. I put a bulb in and discover that the switch on position 2 toggles the light. I would like to put a timer on this light, so I decide to check out the switch to make sure it is a two-pole and to see whether I need a timer with a neutral. I turn off the breaker that controls the patio lights, but the flood light stays on. I basically have to go through the entire box to find the breaker for the floodlight. It's the kitchen breaker, which is weird but I guess I can kind of see how they did it.
Ok, so I turn off both breakers and take off the cover. I stick my voltage meter in and, surprise, position 3 is hot! At this point, I turn off the house power at the panel. I look behind the switches to see what I can see, but I decide I don't want to mess with it. I put the cover back on. After much experimentation, I find that position three toggles the bottom plug on a two-plug receptacle in the living room, which is fed by power on a different circuit. The top plug has continuous power. I have no need for a switched outlet in this room.
When I looked behind the switches, I couldn't see very well, but from what I could see, none of the switches are grounded. The box is metal. I don't think it is grounded. It looks as though all 6 ground wires were capped under one nut. I think the bundle is making contact with the box, but I could not see it screwed to the box. Maybe it is. It also looked as though there was a bundle of neutrals, presumably from more than one circuit.
What can I do with this mess? I probably need a pro, but I'm curious what my options are. In a three-gang metal box, do all three circuits need to be separately ground? Is it ok to combine neutrals? Is three circuits in one box even permitted?
If I decide to take out the switch for the plug in the room, can I simply splice the circuit back together and keep it in the box, or do I need to pull the romex and terminate in the box? Or something else. I haven't looked at the plug device to see what's going on back there.
I guess put more simply, all I care about having at the wall here is the 3-way for the patio lights and a timer for the newly-discovered flood. What are my options?
Best Answer
You can have multiple circuits in one box. But you have to:
So it sounds like the existing setup is a bit strange but not necessarily a problem, in and of itself. Grounding may be an issue, and is the simplest part, so let's tackle that first:
Grounding
Grounding can be through a ground wire or through a metal connection - e.g., metal conduit. In your case, you said "all 6 ground wires were capped under one nut". That sounds like all 3 cables in and all 3 cables out. You're set for grounding.
Box Fill
A box can only hold a certain number of wires and devices. The exact number depends on the dimensions of the box, the size of the wires (12 vs. 14) and a number of other factors. It gets complicated. Assuming that the existing setup is code-compliant, it is quite possible that replacing a simple switch with a timer may cause either code (calculated values) or practical issues with box fill. If that is the case (or "just to play it safe if you're not sure") removing one of the switches would likely solve the problem - giving you more room to work. However, removing a switch leads to...
Switch Requirements
Most rooms are required to have a switched light. Or rather, they have to be designed for a switched light, though nobody can force a homeowner to put in a light (or to change a light bulb that burns out). This can be done using a switched ceiling fixture or (as was the case with my house - first thing I got "fixed" when I moved in) a switched receptacle for a plug-in lamp. That is why you have a switched receptacle.
If you have another switched light in the same room as the switched receptacle then you should be fine. If you do not have a switched light then code may actually require you to keep that switched receptacle (or, alternately, change it to a switched ceiling fixture).
If you do remove a switch, best practice is to either remove the wires or cap them with wire nuts (so they could be used again in the future, and disconnect the wires at the breaker or prior junction so that you don't have extra, unknown, live wires in the box.
Combining Circuits
You may be able to combine circuits. That can help with box fill (both code and practical) because then you can remove some of the cables. However, you need to make sure that you are not going to end up with overloaded circuits. That is generally not a problem with LED lighting, but it is still a consideration. When you have any 3-way circuits you need to make sure that you are combining only at the "incoming power" switch and not at the "other switch" as you could end up with some wacky (and possibly dangerous) situations if you mess that up.
Neutral Problem
Harper pointed out that your neutrals are currently combined between circuits. You can't do that! You will have to match up each neutral with its matching hot/switched hot. Then combine each of those pairs of neutrals together. In the end, the number of neutral groups should be the same as the number of circuit breakers that are related to circuits in this box.
Timers and Neutrals
Many timers, smart switches and other devices require neutral. Code now requires neutral in most switch boxes for that reason. Based on your description, that should not be a problem here, with the possible exception of the 3-way switch (again, if it has "incoming power" then it is fine but the other 3-way likely does not have neutral).