Adding separate wire to convert 6-2 Cable to 6-3 Wiring

Question

I have an installed but not hooked up 6/2 cable (black, white and ground, like this) in my garage for potential future use with an EV charger. I am finishing the garage and will be covering up the cable but am worried that I might actually need a 6/3 cable instead to support a 14-50 receptacle. I prefer the 14-50 as they seem to be more versatile and common for EV charging than say a 6-50.

Similar questions have asked whether existing 6/2 cabling can be used to hook up to a 14-50 as is, or how to run a new wire in parallel. In my case I have the following additional questions:

• Is it safe (I know it is possible) to wire up a 14-50R with a 6/2 cable, leaving the neutral terminal empty?
• Since I still have the walls open, can I run a separate wire like this through the studs alongside the existing 6/2 cable? I.e. am I missing something by not having that wire be part of the sheathing with the 6/2 cable and not armored (as recommended in the linked question above)?

Answer 1

The Code requirement, for good reason, is all conductors must be in the same cable or conduit. I'm not sure whether conduiting this route and stuffing old cable and new wire in the conduit would suffice, that would be up to the local inspector. The conduit would have to be quite large because it would be a nightmare to pull, and because the flat 6-2 cable gets treated same as a round wire of its largest dimension. With 2 "wires" in the conduit, "wires" can only take up 31% of conduit cross section. One thing conduit would be very good for is allowing easy adds and change-ups, extra helpful if you're mudding up the walls! Metal conduit is allowed to serve as the ground wire.

However I would re-cable with 6-3 rather than risk having the inspector redflag it and have to bust out drywall to fix it.

There's no reason to tear the 6-2 out of the wall, unless you have another place to use it (not outdoors, mind). Just bring it into a 120mm (4-11/16") junction box ($2.50 at electrical supply, $5 at big-box) and cap it off at both ends. It can be used later for welders, or EV chargers whose labeling/instructions allow use of a 6-20, 6-30 or 6-50 connection.

You have this. You needed this. Note how many lattés there are in the price difference. I like to use frappucino's (or pizzas) as units of cost savings in cases like this. This case is a glitch, on my screen it shows a $0.02 difference and I suspect normal pricing would put it at 30%.

I find inexperience + savings seeking = this kind of error. A lot. Before you seal up the walls (why do that at all?? It's a garage) I suggest searching for where else this might have been done.

In both the examples you linked, you have lifted out of context.

• The "retrofitting a wire" case, two things wrong there: first it applies only to ground wires, which are a different case because they are not conductors; grounds only carry current during emergencies. And second it applies to old work that was grandfathered because it was legal at the time it was installed. Some people think grandfathering is amnesty for code violations. It's not.
• In the neutralless 14-50, that case talked about the plug, not the socket. That makes all the difference in the world. The plug is free to take only the conductors it needs, but the socket must proffer all the conductors that its design implies. A neutralless 14-x socket could actually cause a deadly problem if you plug in an appliance that had formerly been wired for NEMA 10.

Answer 2

Safe to run a cable without neutral? Sure. If you have a device that doesn't use a neutral then that is perfectly fine.

OK to run a neutral separate from the hots? No. Others can quote the NEC, but the bottom line is that the wires should all be separate wires together in one conduit or use a /3 cable. There are two issues as I understand it:

• Making sure that anything that actually uses a neutral always uses the correct neutral.
• The wires together cancel out each other's magnetic fields. When they are run separately (even a few inches apart) that doesn't happen and, over a long run, can cause problems.

Note that running a neutral separately (bad!) is very different from running a ground separately (good!). There are a number of reasons why retrofit ground is often a good idea (though likely not permitted in this case, for example, because it is a new installation), and since a ground wire does not normally carry any current, the concerns about magnetic fields, heating, etc. are not the same as with a neutral wire. For related reasons, a ground can often be smaller than the associated hot & neutral wires.

There is another advantage to running the neutral (properly) now. That gives you the option of installing a subpanel. You can then connect your EV charger to the subpanel and also additional receptacles, lighting, etc.

Answer 3

Since it's hard to predict future requirements, and since you have the walls open anyway, rip out the cable and install conduit (the flex plastic stuff is easy to install in most situations).

Then pull the individual wires you need. If ever requirements change then new wires can be pulled.

And if you don't need the wires yet you can just install the conduit now, saving the actual wires for later.

(In fact, installing a conduit or two like this is not a bad idea even if you have no anticipated use for it just now. If you need it in the future it will be there.)

Answer 4

That wire we need to be protected in a conduit. So put all 4 in the conduit and a tie wrap in the panel identifying it as part of the circuit (4- 2 ungrounded (hots), 1 grounded (neutral), 1 grounding conductor (EGC).