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NEMA 15-50R to 14-50R

I'm visiting my son in Georgia in a few weeks, and will be taking my new Tesla. His ice cream shop has two ice cream makers that use a 3-phase 15-50R. I'm looking for an adapter to (or make my own) allow the S to charge from those outlets. Am I right in that all I need to do is use 2 out of the 3 legs to get 208V? Is this safe and has anyone been successful in charging the model S on this type of plug?

Thanks!

This is what his plugs look like:

337088-ProductImageURL.jpg
 

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,089
182
Colorado
They are a little pricey, but your idea should work.

HUBBELL HBL8452C AC Plug NEMA 15-50 Male Angled - Electric Plugs - Amazon.com $64.00 + $9.99 shipping

Wiring Diagram 15-50P.PNG


Just remember that this will be the same as a 6-50 to 14-50 adapter. There is no neutral to connect to the neutral in the 14-50. The UMC will work, but label the adapter very well so that an RV user will not use it and blow many of their 120V devices.
 

Cosmacelf

Well-Known Member
Supporting Member
Mar 6, 2013
10,658
34,840
San Diego
Sounds workable, but someone who understands commercial 3 phase power, like FlasherZ, should weigh in. Looks like you would connect the grounds together and then X and Z from the 15-50 to the two hots of the 14-50, and leave the 14-50 neutral unconnected. Use 6 gauge wire for the interconnect.
 

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,089
182
Colorado
Yes, I was thinking of using X/Y and leaving out Z, but I guess it doesn't matter? No need to connect W of the 14-50 to anything?

View attachment 84852 View attachment 84853

Yes, G to G, X to X, and Y to Y should work fine for the Tesla UMC, leaving Z (Phase 3) unconnected on the 15-50 and W (neutral) unconnected on the 14-50. W (neutral) unconnected on the 14-50 can produce unexpected voltage for an RV or other use that is expecting 120 Volts, W to X, and W to Y. That is why the adapter needs to be clearly and boldly labeled "Only for Tesla Charging, Not for RV Use" or something like that.

See NEMA connector - Blade identification - Wikipedia for reference.
 
Yes, G to G, X to X, and Y to Y should work fine for the Tesla UMC, leaving Z (Phase 3) unconnected on the 15-50 and W (neutral) unconnected on the 14-50. W (neutral) unconnected on the 14-50 can produce unexpected voltage for an RV or other use that is expecting 120 Volts, W to X, and W to Y. That is why the adapter needs to be clearly and boldly labeled "Only for Tesla Charging, Not for RV Use" or something like that.

See NEMA connector - Blade identification - Wikipedia for reference.

That's just what I needed, Thanks! I'll test voltages on the 14-50 before I actually connect the UMC to make sure everything looks good!
 

deonb

Active Member
Mar 4, 2013
4,062
4,362
Redmond, WA
W (neutral) unconnected on the 14-50 can produce unexpected voltage for an RV or other use that is expecting 120 Volts, W to X, and W to Y. That is why the adapter needs to be clearly and boldly labeled "Only for Tesla Charging, Not for RV Use" or something like that.

Isn't that just an open circuit? Similar to a circuit with a switch on the neutral.

You typically don't want to switch neutral due to human safety reasons, but it doesn't harm 110V equipment if you do. (It doesn't work of course... but it's not harmful).
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,030
1,030
Isn't that just an open circuit? Similar to a circuit with a switch on the neutral.

You typically don't want to switch neutral due to human safety reasons, but it doesn't harm 110V equipment if you do. (It doesn't work of course... but it's not harmful).

It's not an open circuit. It's very harmful to 120V equipment. Remember that neutral is a grounded center-tap of the transformer that carries the imbalance between leg 1 & leg 2. Allow it to float, and you'll get imbalanced voltages based on the current drawn across the legs.

Imagine appliance 1 between L1 and neutral, and appliance 2 between neutral and L2. Current will flow; the completed circuit is L1-app1-N-app2-L2, with neutral floating.

- - - Updated - - -

Sounds workable, but someone who understands commercial 3 phase power, like FlasherZ, should weigh in. Looks like you would connect the grounds together and then X and Z from the 15-50 to the two hots of the 14-50, and leave the 14-50 neutral unconnected. Use 6 gauge wire for the interconnect.

For most 3-phase power, this will work. You may end up with 208V or 240V, depending on whether it's a wye or delta configuration. The 18-series receptacle is for wye when neutral is required, the 15-series receptacle can be used for delta or wye when only L-L is needed. The wiring Cosmacelf spoke of will work either way. As mentioned, label that adapter 6 ways from Sunday with "NO NEUTRAL - TESLA CHARGING ONLY".
 

deonb

Active Member
Mar 4, 2013
4,062
4,362
Redmond, WA
It's not an open circuit. It's very harmful to 120V equipment. Remember that neutral is a grounded center-tap of the transformer that carries the imbalance between leg 1 & leg 2. Allow it to float, and you'll get imbalanced voltages based on the current drawn across the legs.

Imagine appliance 1 between L1 and neutral, and appliance 2 between neutral and L2. Current will flow; the completed circuit is L1-app1-N-app2-L2, with neutral floating.

Right, of course - you still have the neutral connected between the 2 legs on the other side of the circuit. My bad.
 
It's not an open circuit. It's very harmful to 120V equipment. Remember that neutral is a grounded center-tap of the transformer that carries the imbalance between leg 1 & leg 2. Allow it to float, and you'll get imbalanced voltages based on the current drawn across the legs.

Imagine appliance 1 between L1 and neutral, and appliance 2 between neutral and L2. Current will flow; the completed circuit is L1-app1-N-app2-L2, with neutral floating.

- - - Updated - - -



For most 3-phase power, this will work. You may end up with 208V or 240V, depending on whether it's a wye or delta configuration. The 18-series receptacle is for wye when neutral is required, the 15-series receptacle can be used for delta or wye when only L-L is needed. The wiring Cosmacelf spoke of will work either way. As mentioned, label that adapter 6 ways from Sunday with "NO NEUTRAL - TESLA CHARGING ONLY".

Thanks FlasherZ! I'll be sure to label it properly :)
 

bro1999

Active Member
Apr 26, 2016
2,784
3,569
Maryland
So I am staying at an Airbnb next month, and the house has a "NEMA 15-50 EV charging outlet" included in the listing. I confirmed with the host that it is indeed a 15-50 and not a 14-50 outlet. I tried following the discussion above, but I'm still sorta lost. Is there no simple "plug and play" adapter I could buy that I could use with the UMC to charge from a 15-50 outlet? The Tesla store doesn't list a 15-50 adapter as being available.
 

Cosmacelf

Well-Known Member
Supporting Member
Mar 6, 2013
10,658
34,840
San Diego
So I am staying at an Airbnb next month, and the house has a "NEMA 15-50 EV charging outlet" included in the listing. I confirmed with the host that it is indeed a 15-50 and not a 14-50 outlet. I tried following the discussion above, but I'm still sorta lost. Is there no simple "plug and play" adapter I could buy that I could use with the UMC to charge from a 15-50 outlet? The Tesla store doesn't list a 15-50 adapter as being available.
Unless the Airbnb is in a commercial building, the most likely explanation is that the host is wrong. Have him send you a picture.
 
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