I noticed with a two wire cable (with a ground), the ground and neutral wires in the circuit breaker box all connect together. If I have a two wire only cable to a new three wire receptacle can I install a jumper from the neutral to the ground terminal in the receptacle box with the same results?
Wiring – connect a GFCI outlet’s ground screw to the neutral wire if no ground wire is available
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If your house was wired by a human electrician then I seriously doubt that your gang box has two supply cables with their neutrals connected together. Surely what you think are two supply cables are actually one supply cable and one unswitched load branch leading to at least some of the outlets. All that jumper wire between the switches is how the hot node ultimately reaches the outlets.
If you are intensely curious you could experiment by disconnecting everything and using a contact meter to find which cable supplies power to the gang box. This is probably the only way you will ever obtain true faith in the fact that you don't have two power cables entering the box.
As for validation, you obviously have the box wired at least as correctly as the original electrician did.
Many electricians recommend using "pigtails" to connect the hot node to all the switches and loads, because then a single connection failure will cause only one load to lose power. However, unless you want to use your house as a laboratory to learn the electrician trade, there's no need to change something that's already working.
Each of the 'conduits' as you say, have an uninsulated ground conductor. If there are three such 'conduits' then there has to be a splice joining them. Add your ground there.
I've installed many insteon devices before. The first thing I do, and my best advise, is to spread out all the wiring after removing he old switch and before installing the new, to know absolutely what you have to work with.
If you absolutely have to connect to a ground without cutting and splicing the original, I would recommend a split bolt.
It's going to look weird as hell in an outlet box, but if you thoroughly clean/abrade the existing ground so it makes good contact, a split bolt should do the trick
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Best Answer
Although the neutral wire will generally be near ground potential, there are some situations where it might not be. For example, when switching on a large motor, the voltage on the neutral wire may jump briefly but significantly. Further, if the neutral wire breaks between a device and the panel, it will very likely end up with full line voltage on it. If the neutral wire were bonded to the ground terminal on a piece of equipment, any voltage on it could shock anyone touching the equipment. Because the current would be flowing on the ground wire which the ground-fault interrupter does not switch, the GFCI would provide no protection against it.
The accepted way to handle the situation where no ground is available is to use a GFCI with its ground lead attached to nothing but with a label affixed reading "NO EQUIPMENT GROUND". A GFCI used in such fashion will not detect some failure modes that would be detected if the grounding wire were bonded to neutral but the danger of putting neutral voltage on the ground wire exceeds the safety gain from catching those particular failure modes.
It would be helpful if someone were to sell a GFI which was designed to connect ground to neutral well enough to trip the detector immediately if a device has a leak between its hot and ground leads, but not well enough to pose a dangerous condition. I am unaware of any such devices being for sale, however.