Mobile connector flashes 2x - “ground loss”

[dohmahmigh]

Still waiting to pick up my car but I just got a 14-50 socket installed today and when i plug in the MC, the T flashes 2x, indicating a "ground loss". I measured the voltage across L1-to-ground, L2-to-ground, L1-to-neutral, and L2-to-neutral - they all read ~120V so no issues there. I looked at the ground and neutral to the buses at the panel and they're all tight. When i plug the MC to a 5-15 outlet, it's all green, so don't think it's the MC problem.

Attached a pic of the subpanel. The bottom right 50amp is the MC breaker. Also circled in red are the ground and neutral wire to their respective bus connection.

Any thoughts any one?

 

[Sophias_dad]

FYI, that subpanel looks pretty overloaded based on the perceived gauge of the feeder wire and the new circuit breaker should be GFCI. I see 20+15+50 duplex breakers in there, ignoring all the other breakers and the new 50A for the UMC. Optimistically that MIGHT be 4 gauge good for 85 amps.

It might well be a miswired 14-50 adapter. See if you can find the proper voltages at the end which connects to the UMC body.

 

[dohmahmigh]

That subpanel looks pretty overloaded, and the new circuit breaker should be GFCI.

It might well be a miswired 14-50 adapter. See if you can find the proper voltages at the end which connects to the UMC body.

Thanks for your input. Yeah i'll swap out for a GFCI breaker once it arrives. I just have an extra 50amp breaker lying around so wanted to try it out first.

Don't quite understand what you mean by miswired 14-50 adapter? I used a multimeter to measure the voltage of the receptacle across different pins they all checked out L1/L2-to-neutral/ground all read ~120V. L1-to-L2 reads ~240V

 

[jcanoe]

What brand of 14-50 receptacle? There were reports of some defective Bryant 14-50 receptacles. Usually Hubbell/Bryant (Bryant is now owned by Hubbell) is one of the brands people choose for a reliable 14-50 receptacle.

 

[Sophias_dad]

Thanks for your input. Yeah i'll swap out for a GFCI breaker once it arrives. I just have an extra 50amp breaker lying around so wanted to try it out first.

Don't quite understand what you mean by miswired 14-50 adapter? I used a multimeter to measure the voltage of the receptacle across different pins they all checked out L1/L2-to-neutral/ground all read ~120V. L1-to-L2 reads ~240V

That foot-long connector between the UMC and the plug might have been made incorrectly so regardless of what the outlet is providing, the UMC might not be seeing it.

 

[dohmahmigh]

What brand of 14-50 receptacle? There were reports of some defective Bryant 14-50 receptacles. Usually Hubbell/Bryant (Bryant is now owned by Hubbell) is one of the brands people choose for a reliable 14-50 receptacle.

Using the hubbell as many recommended

 

[dohmahmigh]

That foot-long connector between the UMC and the plug might have been made incorrectly so regardless of what the outlet is providing, the UMC might not be seeing it.

So to be clear, you’re talking about the adapter that Tesla seller many different versions of eg 14-50, 14-30, 5-15, etc right? If so, how do I test that? Just stick the probes of the multimeter in? To which pins/holes?

 

[Sophias_dad]

So to be clear, you’re talking about the adapter that Tesla seller many different versions of eg 14-50, 14-30, 5-15, etc right? If so, how do I test that? Just stick the probes of the multimeter in? To which pins/holes?

Yes, that's what I'm asking about. The pinout is available online somewhere, or at least it should be easy to figure out.

 

[OxBrew]

Is the neutral bus bonded to the panel? Not supposed to be in a sub panel. Not sure how the MC could tell if it was, just something to check.

(there's normally a screw that should be removed so there's no connection between neutral bus and the box, and you should be able to see the empty hole)

Also, be sure the box is properly grounded first, I don't see an obvious ground bond wire, usually a bit bigger, and attached to a ground rod outside (or 2 ground rods)

So the neutral feed might be providing the only "ground" path right now.

 

[jcanoe]

I would double check the torque on the screws of the wire termination for the Hubbell 14-50 receptacle. Unless you have an electrician's experience you really need to use a torque screwdriver to properly torque the allen head screws and lug type terminals used on the Hubbell 14-50R to the correct 75 inch-pound spec (not the usual 25 inch-pound torque.)

 

[stopcrazypp]

I would check the ground connection at your outlet where you put your 14-50. It seems you didn't check that yet. Take the outlet out and see if the connections are properly made. Check for continuity between ground wire and the ground pin. There is a possibility your ground wire might be a bit thin for the clamp, in which case doubling up or using a pigtail might be best.

FYI the Mobile connector doesn't even use the neutral in the 14-50 (if you measure continuity on the other end of adapter it is not connected to anything), it only uses the ground pin, so that is critical.

 

[dohmahmigh]

I would double check the torque on the screws of the wire termination for the Hubbell 14-50 receptacle. Unless you have an electrician's experience you really need to use a torque screwdriver to properly torque the allen head screws and lug type terminals used on the Hubbell 14-50R to the correct 75 inch-pound spec (not the usual 25 inch-pound torque.)

Thanks. Will double check that later on

 

[dohmahmigh]

I would check the ground connection at your outlet where you put your 14-50. It seems you didn't check that yet. Take the outlet out and see if the connections are properly made. Check for continuity between ground wire and the ground pin. There is a possibility your ground wire might be a bit thin for the clamp, in which case doubling up or using a pigtail might be best.

FYI the Mobile connector doesn't even use the neutral in the 14-50 (if you measure continuity on the other end of adapter it is not connected to anything), it only uses the ground pin, so that is critical.

How do I “Check for continuity between ground wire and the ground pin”?

 

[dohmahmigh]

Is the neutral bus bonded to the panel? Not supposed to be in a sub panel. Not sure how the MC could tell if it was, just something to check.

(there's normally a screw that should be removed so there's no connection between neutral bus and the box, and you should be able to see the empty hole)

Also, be sure the box is properly grounded first, I don't see an obvious ground bond wire, usually a bit bigger, and attached to a ground rod outside (or 2 ground rods)

So the neutral feed might be providing the only "ground" path right now.

I believe the neutral and ground are bonded at main service panel that’s located in the back of the house before coming into the subpanel.

 

[mongo]

Still waiting to pick up my car but I just got a 14-50 socket installed today and when i plug in the MC, the T flashes 2x, indicating a "ground loss". I measured the voltage across L1-to-ground, L2-to-ground, L1-to-neutral, and L2-to-neutral - they all read ~120V so no issues there. I looked at the ground and neutral to the buses at the panel and they're all tight. When i plug the MC to a 5-15 outlet, it's all green, so don't think it's the MC problem.

Attached a pic of the subpanel. The bottom right 50amp is the MC breaker. Also circled in red are the ground and neutral wire to their respective bus connection.

Any thoughts any one?

I may be missing it, but I don't see a ground feed to the breaker panel.

 

[stopcrazypp]

How do I “Check for continuity between ground wire and the ground pin”?

Since the ground wire is just bare, this should be easy. In practically every multimeter there is a continuity mode (many will beep). Stick one probe into the ground pin of the outlet, have one probe on the bare ground wire.

If you want to check the ground pin to panel, it'll be a lot harder given your probes can't reach that far (for mine personally, my 14-50 is right under my subpanel so I can even easily check the panel connection too).

As others mentioned however, your subpanel doesn't appear to have a ground wire from your main panel. That might be the cause of the issue. Is your subpanel perhaps bonded via the conduit from main panel to subpanel? Those conduit connections sometimes can be iffy, and if the conduit is buried, it may have corroded, which would cause poor grounding.

It may be tough to check that if your subpanel is far away from your main panel. The only way I can think is to get a wire, measure its resistance (this wire is essentially functioning as an extension cord for one of your probes). Then connect the wire to the ground on one of the panels and bring the wire to the other panel, then measure resistance again at the ground connection at the second panel. The additional resistance would essentially be the resistance from your main to subpanel.

In my subpanel, there is a grounding bushing and a jumper wire that connects to the ground terminals in the subpanel (although it looks like an actual green jacketed ground wire through the conduit that loops through that bushing), which ensures a good ground connection from conduit. Something that looks kind of like this (just a quick example, may not necessarily be compatible):

https://www.lowes.com/pd/Sigma-Elec...al-Conduit-Compatible-Conduit-Fitting/3392512

 

[mongo]

Is the neutral bus bonded to the panel? Not supposed to be in a sub panel. Not sure how the MC could tell if it was, just something to check.

(there's normally a screw that should be removed so there's no connection between neutral bus and the box, and you should be able to see the empty hole)

Also, be sure the box is properly grounded first, I don't see an obvious ground bond wire, usually a bit bigger, and attached to a ground rod outside (or 2 ground rods)

So the neutral feed might be providing the only "ground" path right now.

Missed that you also called out not seeing ground feed.
Since this is a sub panel, it should be a green (or green tape wrapped if > 6 AWG) insulated wire from the main panel ground bus.

 

[dohmahmigh]

Missed that you also called out not seeing ground feed.
Since this is a sub panel, it should be a green (or green tape wrapped if > 6 AWG) insulated wire from the main panel ground bus.

Thanks y’all for the input so far. I’ve taken a few more pics of the set up.

1st pic is the main panel. It looks like the ground and the neutral are bonded as I see bare wire and white wire connected to the same bus. Is that right?

2nd pic shows two bare wires leaving the box. Left conduit goes straight to the ground and the right conduit turns towards the garage.

3rd pic shows where the right conduit in the 2nd pic ends but with a metal wire (painted in greyish color) sticking out and continues thru the wall into the garage

4th pic shows that greyish wire connected to a gas pipe.

Since I have extra 6awg wire left, i pulled out 3 of the wires from inside and connect them so it’s long enough for me to connect from the gas pipe to the ground bus in the subpanel.

But unfortunately same issue persists.

Do I need a bigger gauge wire to make that ground connection from the gas pipe to the subpanel ground bus?

Thanks y’all!

 

[ShawnA]

Hi @dohmahmigh ,

I'm sorry if I missed it but I do not see the external ground in your main panel...

The ground wire as others have mentioned may be a large bare copper wire...
Sometimes a ground wire is bonded to a WATER pipe but I have never heard
and would be afraid of a ground wire bonded to a GAS pipe.

Your main service ground should be connected to a 6 foot or 8 foot copper
rod driven into the ground near your service entrance which is near the
electric meter...

Good luck,

Shawn

 

[OxBrew]

Yeah.

So is the pic of the full panel with all the breakers a sub panel, maybe in the garage?

Sub panels need separate ground rods. Neutrals need to be not bonded to the box. (remove the special screw that electrically connects the neutral bus to the sub panel box)

The main panel SHOULD be bonded ground to neutral, that is the ONLY place they are bonded together, so that is correct.

Can you take a new pic of the sub panel, with the new ground bond?

Edit: Ok, I think I understand. The main panel is just the 125A breaker. I think the sub panel should have its own ground bond straight down to the ground rod, and no ground wire between the sub and main panels.

And gas lines absolutely do need to be bonded to water lines, usually at the water heater, just since they are close together. And water bonded to the ground rod, usually at the main panel.

Neither water or gas can be a substitute for a ground rod, there's no guarantee they are actually grounded. Could have a repair somewhere up stream with a section of plastic pipe, or not making good earth contact.

Best is to install 2 ground rods 6ft apart and bond them per code. It's easy.