Installing nema 14-50 with no ground

Question

Good morning,

Im in the US and I have a problem that I can't seem to find a straight answer for.

I recently bought a new range and the receptacle was a 3 prong but the oven uses a 4 prong cord. I see a lot of people with this issue but the details are a little different.

The previous receptacle was a nema 10-50 and there are only 3 wires coming out of the box, a red, black and white. No ground. I found a video explaining that it's fine to hook the new 14-50r without a ground (just connect the 2 hot and 1 neutral) so I did that. I turned it on and everything appears to be working great. My question is if this is safe or not because aside from that video I haven't seen anyone else online do this same thing.

Any advice would be greatly appreciated

Answer 1

Nope, no good.

The right thing to do in this situation is not to just omit the equipment ground wire from the four-wire receptacle as if it was optional. It will operate, but it will not be code compliant, and it won't be as safe as it could or should be. That wire is after all the safety ground.

If you aren't prepared to run a ground wire for the circuit, the right thing to do in this situation is use the three-wire receptacle, and change the appliance cord to a three-wire, making the connections inside according to the manufacturer's instructions for a three-wire cord. It's a simple fix, easy, inexpensive, code compliant, and reasonably safe. There are literally millions of ranges and dryers installed this way in older homes in the US.

With most ranges and dryers, the instructions will show how to connect your cord if you're using a receptacle without an equipment ground. The connection generally bonds the neutral to the frame of the appliance. While this is not quite as safe as a four-wire circuit wired with an equipment ground, it does provide protection / fault clearing in case of an internal ground fault in the appliance. Here's an example:

from a power company handout.

If you have a four wire cord with the usual four-wire connections inside the appliance, but the equipment ground goes nowhere in that receptacle, you have no fault clearing for those internal ground faults, which is potentially dangerous.

If someone knew what they were doing, I suppose they could use a four-wire cord with a four-wire receptacle that has no equipment ground, but bond neutral to ground inside the appliance like you would with a three-wire cord. You would have the same fault-clearing you'd have with a three wire cord. But that's still a bad idea. For one thing, if anyone ever corrects the wiring of the receptacle, but assumes the appliance is wired normally - a reasonable assumption - they will not remove the bond / jumper inside, and it will create a dangerous configuration where you have unwanted current on the equipment ground. But if they know what they're doing, wouldn't they just do it the right way?

In addition, since the instructions for the four-wire receptacle don't make that equipment ground optional, it's a code violation to install the receptacle without the ground. Even if it was not a code violation, it's a common sense violation. When someone sees a NEMA 14-50R it's reasonable for them to assume there's an equipment ground, and if they plug in equipment wired for that equipment ground, they will unknowingly create an unsafe situation.

Answer 2

I found a video explaining that it's fine to hook the new 14-50r without a ground (just connect the 2 hot and 1 neutral) so I did that. I turned it on and everything appears to be working great.

Did this video include the words "challenge" or "hold my beer"? It should have... yes, Youtube is horrible for electrical advice. Come here; we have an upvote/downvote system where a bad answer like that will get downvoted.

Step 1: See if your wires are illegal.

Look at the neutral. If it's insulated white, or a web of bare wires that were wrapped around the hots, that is acceptable. Look at the 2 hots, if they're both NOT white, that is acceptable.

If you have a white hot or a solid bare neutral, that cable was illegal the day it was installed and it needs to go.

If the cable is illegal, the whole cable needs to be replaced anyway. You can't use 10/2 cable (it's obviously illegal) so you must use 10/3 with ground wire. Problem solved.

Step 2: See if you actually do have a ground.

You have to look at the wires coming into a metal box. There may be a ground wire that was terminated at the box metal instead of the recep; that is fine actually. Grounds are supposed to go to the box metal first, and can be carried to the recep via the metal-metal contact between recep and box.

Next, check for metal conduit - if it's 3 loose insulated wires going into a pipe (white or gray neutral, and any other color hots), then you probably have ground via the metal conduit. Again the receptacle can pick up ground via the metal box.

If you don't have a ground wire or conduit...

You have 2 available plays.

#1 you can retrofit just a ground wire. It needs to be #10 and can go to any junction box where a #10 or larger ground wire goes back to the panel, or metal conduit goes back to the panel, or it can go to the bare copper wires that run between the main panel and the grounding rods. Do not attach to plumbing pipe.

#2 you can skip running the ground wire and install a 2-pole 50A GFCI breaker in the panel. Label the receptacle "GFCI Protected" - "No Equipment Ground".

In both these scenarios, you can install a NEMA 14-50 receptacle properly and legally.

Otherwise, it is legal to continue a 10-50 in service

But not all that safe. If there is a problem with the neutral wire, the chassis of the range WILL be energized. Now as you know, most of the time when people get an electric handshake, they get lucky and don't die. Do not interpret this as "humans are immune to electricity"; they're not and the wrong set of circumstances can converge to kill you anytime there is an unsafe condition.

The problem with a 3-wire range connection is there are no layers to the onion. Mains electrical is designed so there must be a chain of several failures (and at least one code violation) to create an unsafe situation. Not here. You are exactly 1 routine/expectable failure away from a lethal situation. When a wire just breaks, that's not even a Code violation,

If you simply can't change the wiring, the 2-pole GFCI breaker + 14-50 recep is the best option.

However if the wiring is illegal, you must change the wiring.

Remember to un-jumper the range!!!

The dryer will have a jumper to connect (or not connect) dryer neutral to chassis. You must take care to remove that jumper if you use a NEMA 14-50 connection, so that neutral is isolated from ground at the range. (if you use a GFCI breaker, that will enforce this).

I cannot in good faith ever recommend someone connect a machine's chassis to its neutral, but that is what you must do with a 3-wire NEMA 10-30 connection, because the UL approved instructions require that, and that exception was carved into NEC for 3-wire legacy installations of dryers and ranges. If it were me, I'd pursue one of the other options above.

Edit: I inadvertently said "dryer" and "30A" several places. Ranges and dryers have the exact same issue.

Answer 3

There is a reason that the code was changed to 3 wire + safety ground. Many people, including myself, have been tingled, badly shocked or killed by touching a kitchen range and a sink faucet, metal sink or refrigerator simultaneously where the range was on a 3 wire circuit. The frame of the range must be connected to the safety ground (green). The reason that the code was not changed to mandate upgrading obsolete 3 wire (black, red, white) receptacles to 4 wire (black, red, white, green) is that millions of installations would be made illegal and the political backlash would be intolerable.