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NEMA 10-30 adapter + NEMA 14-50 extension cord

PoitNarf

My dog's breath smells like dog food
Jun 7, 2016
2,870
4,317
NJ
Just came back from a trip to my family’s vacation house up in Cape Cod MA. There are three superchargers planned for Cape Cod in the near future, but as far as I know construction has not started on any of them. Since the closest supercharger was a 45 minute drive away I needed to be able to charge at a decent rate at the house. Luckily the dryer at the house was switched from electric to gas at some point, so there was an unused but still active NEMA 10-30 outlet in the basement. I went on Amazon and bought myself a NEMA 10-30 to 14-50 adapter, https://www.amazon.com/dp/B06VWGVQDF/ref=cm_sw_r_cp_api_i_mK8dBb8FAM5M2, and a 30 foot NEMA 14-50 extension cord, https://www.amazon.com/dp/B0024ECIP0/ref=cm_sw_r_cp_api_i_WL8dBb3Z0N6AN.

This solution worked out very well. Obviously I had to bump the amps down to 24 since I was charging from a 30 amp circuit. This is very important since I had the 14-50 adapter plugged into my UMC, so my Model 3 assumed it could go the full 32 amps. With the max draw at 24 amps I was able to get 23 miles per hour of charge. Roughly half of the charge rate I get at home with my wall connector. Eventually I’d like to install an actual 14-50 outlet so I can get the full charge rate out of my UMC. Here’s some photos for any that are looking to implement a similar solution.

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Electrastg

Member
May 5, 2018
9
8
St. George, Utah
I ran a permanent outlet from my unused dryer outlet into my garage and installed a 14-50 outlet so I could use the adapter that comes with the M3. The adapter doesn't know what amp and voltage is going through it. Just had to set the amperage down to 24 amps. as recommended since the circuit was 30amps. Mine charges at 24miles/hr. Tesla provides an excellent interface to adjust to individual circumstances.

On another charging subject:

I was considering a route the other day in an area where there aren't many superchargers and realized that there are numerous RV parks around the country that supply 240v 50amp circuits. If in a pinch just stop by one to get topped up. I am sure you can get a charge at a reasonable price.
 

cybergates

Member
Feb 14, 2017
550
240
So Cal
I ran a permanent outlet from my unused dryer outlet into my garage and installed a 14-50 outlet so I could use the adapter that comes with the M3. The adapter doesn't know what amp and voltage is going through it. Just had to set the amperage down to 24 amps. as recommended since the circuit was 30amps. Mine charges at 24miles/hr. Tesla provides an excellent interface to adjust to individual circumstances.

On another charging subject:

I was considering a route the other day in an area where there aren't many superchargers and realized that there are numerous RV parks around the country that supply 240v 50amp circuits. If in a pinch just stop by one to get topped up. I am sure you can get a charge at a reasonable price.

i extended my unused dryer outlet too - but put a 14-30 socket instead and then 14-30 tesla adapters for gen 1 or gen 2 that auto-reduce to 24 amps are available from the tesla website. They have 10-30 adapters too
 
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cybergates

Member
Feb 14, 2017
550
240
So Cal
Just came back from a trip to my family’s vacation house up in Cape Cod MA. There are three superchargers planned for Cape Cod in the near future, but as far as I know construction has not started on any of them. Since the closest supercharger was a 45 minute drive away I needed to be able to charge at a decent rate at the house. Luckily the dryer at the house was switched from electric to gas at some point, so there was an unused but still active NEMA 10-30 outlet in the basement. I went on Amazon and bought myself a NEMA 10-30 to 14-50 adapter, https://www.amazon.com/dp/B06VWGVQDF/ref=cm_sw_r_cp_api_i_mK8dBb8FAM5M2, and a 30 foot NEMA 14-50 extension cord, https://www.amazon.com/dp/B0024ECIP0/ref=cm_sw_r_cp_api_i_WL8dBb3Z0N6AN.

This solution worked out very well. Obviously I had to bump the amps down to 24 since I was charging from a 30 amp circuit. This is very important since I had the 14-50 adapter plugged into my UMC, so my Model 3 assumed it could go the full 32 amps. With the max draw at 24 amps I was able to get 23 miles per hour of charge. Roughly half of the charge rate I get at home with my wall connector. Eventually I’d like to install an actual 14-50 outlet so I can get the full charge rate out of my UMC. Here’s some photos for any that are looking to implement a similar solution.

I use essentially the same situation but from 14-30 adapter --> 14-50 and then a 14-50 15 foot cord (essentially same cord shorter length). From there I could use a 14-50 but worry about manually dialing amps down. One could either cut the neutral pin on a 14-30 tesla adapter adn use that to auto-reduce to 24 amps (goof proof). Or use this funky pigtail adapter that takes a 14-50 plug --> 14-30 sockets (yeah 2 of them but I just use 1). I have this one screwed to the wall so its secure. https://www.amazon.com/gp/product/B00SJESJU2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

A 14-30 cord would just simplify things but I like the option to be able to take the 14-50 extension on road trips.
 

eprosenx

Active Member
May 30, 2018
2,075
2,541
Beaverton, OR
I ran a permanent outlet from my unused dryer outlet into my garage and installed a 14-50 outlet so I could use the adapter that comes with the M3. The adapter doesn't know what amp and voltage is going through it. Just had to set the amperage down to 24 amps. as recommended since the circuit was 30amps. Mine charges at 24miles/hr. Tesla provides an excellent interface to adjust to individual circumstances.

This violates code and I *HIGHLY* don't recommend it for a permanent install situation that you use frequently without direct supervision. I hear in the forums that the Tesla's sometimes "forget" that you have dialed the amperage down for a given location of charge and so it may try to draw too much current. You don't want to rely on the breaker operating properly to resolve that dangerous situation. The NEC relies both on things being engineered/installed properly to not cause an overcurrent situation PLUS then fuses/breakers as an added layer of safety. Putting a 50a plug on a 30a circuit takes away one level of safety (note that it is dumb in this country that you are allowed to use a 50a plug on a 40a circuit in some situations, but certainly not a 30a circuit).

If you can't run a direct 50a back to the panel (which is what optimally I would do in all situations), you should downgrade your plug to a 30a plug and just get the correct UMC adapter so there is no chance of it trying to draw more than 24a.
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,780
22,251
San Diego
This violates code and I *HIGHLY* don't recommend it for a permanent install situation that you use frequently without direct supervision. I hear in the forums that the Tesla's sometimes "forget" that you have dialed the amperage down for a given location of charge and so it may try to draw too much current. You don't want to rely on the breaker operating properly to resolve that dangerous situation. The NEC relies both on things being engineered/installed properly to not cause an overcurrent situation PLUS then fuses/breakers as an added layer of safety. Putting a 50a plug on a 30a circuit takes away one level of safety (note that it is dumb in this country that you are allowed to use a 50a plug on a 40a circuit in some situations, but certainly not a 30a circuit).

If you can't run a direct 50a back to the panel (which is what optimally I would do in all situations), you should downgrade your plug to a 30a plug and just get the correct UMC adapter so there is no chance of it trying to draw more than 24a.

I agree. The correct Tesla adapter for a 14-30 or 10-30 plug is only $45 or so. Change out the 14-50 to whatever type of dryer outlet you have, get the correct Tesla adapter, and all will be well in the universe.
 

timk225

Active Member
Mar 24, 2016
2,050
2,305
Pittsburgh
In that photo of your blue 3 with the charging cable, I noticed that your center hub cap and lug nut cover kit isn't installed properly. The vertical line of the Tesla "T" should be pointing at the valve stem. Why? I don't know, it just seems like a good standard to set for attentive 3 owners.
 
Last edited:

PoitNarf

My dog's breath smells like dog food
Jun 7, 2016
2,870
4,317
NJ
In that photo of your blue 3 with the charging cable, I noticed that your center hub cap and lug nut cover kit isn't installed properly. The vertical line of the Tesla "T" should be pointing at the valve stem. Why? I don't know, it just seems like a good standard to set for attentive 3 owners.

Nope, it’s yours that is not installed correctly. All of the Ts on my wheels are pointing dead center at one of the lug nuts. That has more symmetry to it ;)
 

Electrastg

Member
May 5, 2018
9
8
St. George, Utah
I agree. The correct Tesla adapter for a 14-30 or 10-30 plug is only $45 or so. Change out the 14-50 to whatever type of dryer outlet you have, get the correct Tesla adapter, and all will be well in the universe.
Thanks for the feedback. I have an adapter on order and will swap out the outlet so there aren't any problems in the future.
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,780
22,251
San Diego
Thanks for the feedback. I have an adapter on order and will swap out the outlet so there aren't any problems in the future.

Yeah, the problem is that when you sell your house, the last thing on your mind is going to be that receptacle which isn’t to code. If the buyer hired a home inspector, they might make you switch it out anyways.

Anyways, it will make it easier for you since you won’t have to make sure the amps are set correctly.
 
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eprosenx

Active Member
May 30, 2018
2,075
2,541
Beaverton, OR
Yeah, the problem is that when you sell your house, the last thing on your mind is going to be that receptacle which isn’t to code. If the buyer hired a home inspector, they might make you switch it out anyways.

Hah, I *highly* doubt any home inspector would catch that. I don't think they generally go through and check the entire electrical system for compliance. They are usually just looking for anything really obviously wrong.

But yes, best to just do it right/safe up front!
 

eprosenx

Active Member
May 30, 2018
2,075
2,541
Beaverton, OR
This violates code and I *HIGHLY* don't recommend it for a permanent install situation that you use frequently without direct supervision. I hear in the forums that the Tesla's sometimes "forget" that you have dialed the amperage down for a given location of charge and so it may try to draw too much current. You don't want to rely on the breaker operating properly to resolve that dangerous situation. The NEC relies both on things being engineered/installed properly to not cause an overcurrent situation PLUS then fuses/breakers as an added layer of safety. Putting a 50a plug on a 30a circuit takes away one level of safety (note that it is dumb in this country that you are allowed to use a 50a plug on a 40a circuit in some situations, but certainly not a 30a circuit).

If you can't run a direct 50a back to the panel (which is what optimally I would do in all situations), you should downgrade your plug to a 30a plug and just get the correct UMC adapter so there is no chance of it trying to draw more than 24a.

I may have to eat my own words on this one. I just was reading really deep into the code to verify that you are allowed to do a NEMA 14-50 receptacle on a 40 amp circuit and I realized that the only actual code requirement I find for situations where you only have a single receptacle on a single circuit is:

NEC 210.21(B)(1)
"Single Receptacle on an Individual Branch Circuit
A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit."

By my reading, that would allow you to put a NEMA 14-50 receptacle on a 30a rated circuit.

Now if you have multiple outlets on the same circuit then the restriction to 40a or 50a receptacles applies and I think it is only allowed for electric ranges (in residential settings), but for single outlets on a circuit I think the above applies...

So yeah, what you did might not actually violate code by itself as long as you kept the 30a breaker, but I still would highly recommend installing a 30a receptacle so that you don't forget to crank the setting down (or the Tesla "forgets" for you) and you blow the breaker...

Though actually, since your *intended* use for that plug is for a Gen 2 UMC with a NEMA 14-50 tip which will draw up to 32 amps per its nameplate rating, it still violates code due to the "continuous loads" not being allowed at greater than 80% of the rating of the circuit.

Once you switch the tip on the UMC to a 30a one though its nameplate value is changed to 24a so it is totally fine then.

Clear as mud?
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,780
22,251
San Diego
oops, I forgot about the dedicated circuit rule. By code, I don’t think you are allowed to extend a NEMA 14-30 receptacle. To be truly compliant, you should remove the dryer receptacle and blank faceplate it so that there aren’t two receptacles off that same circuit. We’re really nitpicking now,..
 

cybergates

Member
Feb 14, 2017
550
240
So Cal
oops, I forgot about the dedicated circuit rule. By code, I don’t think you are allowed to extend a NEMA 14-30 receptacle. To be truly compliant, you should remove the dryer receptacle and blank faceplate it so that there aren’t two receptacles off that same circuit. We’re really nitpicking now,..

That's what I did with mine. Blank plate and that old "leg" is disconnected inside a attic junction box with a new leg to the garage.
 

SigNC

Active Member
Aug 23, 2017
1,572
1,480
NC
I use the exact same setup as the OP because it allowed me to leverage a single 14-50 extension in multiple situations.
 
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eprosenx

Active Member
May 30, 2018
2,075
2,541
Beaverton, OR
oops, I forgot about the dedicated circuit rule. By code, I don’t think you are allowed to extend a NEMA 14-30 receptacle. To be truly compliant, you should remove the dryer receptacle and blank faceplate it so that there aren’t two receptacles off that same circuit. We’re really nitpicking now,..

Oh yes, when he said he "extended" it I assumed that meant he spliced into the end of the circuit in an electrical box and extended it to another electrical box with a receptacle. Plugging in to do the extension I presume is not compliant (but I honestly have not gone and looked it up).

I should also call out that last night I found a new NEC code section specifically for electric vehicle wiring. Section 625 of the 2017 code. Some good nuggets in there. You can register for free access to the code so you don't have to pay the stupid money for the book if you want to look at it.
 

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