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14-30 extension cord

Nole

Member
Nov 5, 2019
11
2
Vancouver Island
hi all. I have a 14-30 outlet in my basement. Unfortunately it is 40 ft from where the new M3+ will be parked in our carport. I am having trouble sourcing a cord up here in BC. The L14-30 cords are available but I believe these are for generators. My question is can I use the L14-30 cord to charge the car? I have ordered the Tesla 13-30 adapter. Thanks in advance.
 

ilyak

Member
Mar 16, 2019
604
712
Walpole, NH
Edit: never mind, I’ve not had my coffee yet - you’re asking about a 14-30, not a 10-30. EVSE does make adapters for 14-30 to 14-50 too, but extension cord availability for 14-30 should be much better than for 10-30, so you don’t need it.

Disclaimer: this is officially not recommended by the manual and may be against the electric code for your location.

With the above said, I have previously successfully used the following set up as a temporary solution:
EVSE 10-30 to 14-50 adapter: NEMA 10-30P to 14-50R Adapter – EVSE Adapters
14-50 extension cord: https://www.smile.amazon.com/dp/B078M7ZFHN/ref=cm_sw_r_cp_api_i_4ov0DbK0JTE0W
Tesla 14-50 pigtail adapter

Since you’re using a 30 amp outlet, you’ll need to set the maximum current to 24A in the car. Also, be sure to properly test your 10-30 and verify that the wire gauge is sufficient for a 24A load - those outlets are typically old and not always installed to code.
 

kkillebrew

Banned
Jun 23, 2019
401
123
austin, tx
I had the exact same issue at my lake house cabin. You can do what you ask yes, but it will require additional adapters and will be expensive. I ended up making one for a simpler, cheaper, safer, higher amp solution. Use 12AWG rubberized stranded three wire cable. If you are okay with charging at 20 to 24 amps. Get it in precut lengths in the RV sections of hardware stores - not electrical for the best price. Home Depot has it in 25 and 50 ft lengths. UL approved 14-30 plug kits ($20 usually configurable to 14-50 as well) and enclosed outlets (Leviton under $10) are usually across the isle.
 

Nole

Member
Nov 5, 2019
11
2
Vancouver Island
I had the exact same issue at my lake house cabin. You can do what you ask yes, but it will require additional adapters and will be expensive. I ended up making one for a simpler, cheaper, safer, higher amp solution. Use 12AWG rubberized stranded three wire cable. If you are okay with charging at 20 to 24 amps. Get it in precut lengths in the RV sections of hardware stores - not electrical for the best price. Home Depot has it in 25 and 50 ft lengths. UL approved 14-30 plug kits ($20 usually configurable to 14-50 as well) and enclosed outlets (Leviton under $10) are usually across the isle.
I guess that would be the way to go. I don’t want to have to remember to dial the amps down to 24 all the time.
Keep it simple stupid is my motto. Thanks.
 
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eprosenx

Active Member
May 30, 2018
2,065
2,483
Beaverton, OR
I had the exact same issue at my lake house cabin. You can do what you ask yes, but it will require additional adapters and will be expensive. I ended up making one for a simpler, cheaper, safer, higher amp solution. Use 12AWG rubberized stranded three wire cable. If you are okay with charging at 20 to 24 amps. Get it in precut lengths in the RV sections of hardware stores - not electrical for the best price. Home Depot has it in 25 and 50 ft lengths. UL approved 14-30 plug kits ($20 usually configurable to 14-50 as well) and enclosed outlets (Leviton under $10) are usually across the isle.

I would highly recommend adding a new receptacle or extending where the current one is located rather than using an extension cord. Extension cords add risk and so they are not recommended.

With that being said, too can build what you need (or have someone make it for you easily).

But please. Do NOT do what was suggested above. 12 gauge is only supposed to be used for 20a (16a continuous for EV charging). You should use 10 gauge for 30a (24a continuous).
 

kkillebrew

Banned
Jun 23, 2019
401
123
austin, tx
I would highly recommend adding a new receptacle or extending where the current one is located rather than using an extension cord. Extension cords add risk and so they are not recommended.

With that being said, too can build what you need (or have someone make it for you easily).

But please. Do NOT do what was suggested above. 12 gauge is only supposed to be used for 20a (16a continuous for EV charging). You should use 10 gauge for 30a (24a continuous).
That ampacity rating refers to a 100 ft run of in wall romex, not an extension cord. Do the math and you will see there is no problem with 12 gauge in this situation. In any case he could just go to #10. Of course adding a receptacle is better duh... but the premise is is that he wants or needs an extension cord. And the attitude that you need someone to actually build that for you? Are you an electrician?

All that being said @epersonx is basically correct. 40ft is too long for an extension even though it can successfully be done. If your breaker box is more that 60ft from your outlet you may have trouble no matter what.
 
Last edited:

eprosenx

Active Member
May 30, 2018
2,065
2,483
Beaverton, OR
That ampacity rating refers to a 100 ft run of in wall romex, not an extension cord. Do the math and you will see there is no problem with 12 gauge in this situation. In any case he could just go to #10. Of course adding a receptacle is better duh... but the premise is is that he wants or needs an extension cord. And the attitude that you need someone to actually build that for you? Are you an electrician?

All that being said @epersonx is basically correct. 40ft is too long for an extension even though it can successfully be done. If your breaker box is more that 60ft from your outlet you may have trouble no matter what.

So ratings for line cord (like SOOW or SJOOW) are indeed different than in wall conductors like NM cable or THHN, but I don’t think 12 gauge is OK in any way for 24 amps continuous. I don’t know all the UL/NEC details that may or may not apply to this, but I don’t know of any reputable manufacturers that make 14-30 cords with a gauge as thin as 12 gauge.

Not to mention that the voltage drop for 24 amps on only 12 gauge wire would be large. I would need to run the math, but that may too may be a limiting factor.

The reason I mentioned having someone build it for you is that there are folks that can do it better / cheaper than perhaps you can in the field. Specifically, I have been ordering L14-30 generator extension cords from IronBox (via Amazon). While the ones I have been getting are not moulded, they can make moulded ones also that require high temp injection molding equipment that I personally don’t have.
 
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user212_nr

Active Member
Aug 26, 2019
1,407
737
US
hi all. I have a 14-30 outlet in my basement. Unfortunately it is 40 ft from where the new M3+ will be parked in our carport. I am having trouble sourcing a cord up here in BC. The L14-30 cords are available but I believe these are for generators. My question is can I use the L14-30 cord to charge the car? I have ordered the Tesla 13-30 adapter. Thanks in advance.

An extension cord is basically just a wire with a few properties:
1) An outlet on one end and a plug on the other
2) A massive amount of rubber that is used for
___ a) keeping someone from cutting it
___ b) waterproofing
3) stranded wires that are more flexible
4) they are rated by the number of amps they can carry, for the sake of less technical persons

These are all things which make the wire more expensive and things which you don't want in your situation.

What you want is actually called a "wire" and its not that big of deal to plug it into your outlet as an "extension". An extension cord is just a waste of money. The wire can then be stapled to the wall and will be a semi-permanent solution.
 

user212_nr

Active Member
Aug 26, 2019
1,407
737
US
Online Wire Size Calculators & Tables

Screen Shot 2019-11-20 at 12.41.59 PM.png
 
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eprosenx

Active Member
May 30, 2018
2,065
2,483
Beaverton, OR

8 AWG is likely overkill.

The load should only be 24 amps on a 30a circuit (for EV charging). So that is what you would calculate the voltage drop as.

Also, 3% voltage drop is allowable. EV’s are not going to have a problem with a lower voltage as long as it is not such a swing on voltage between the starting voltage and the voltage under load that the car stops charging due to it thinking there is something wrong.
 
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ivy_

Member
Sep 25, 2019
144
140
Michigan
8 AWG is likely overkill.

The load should only be 24 amps on a 30a circuit (for EV charging). So that is what you would calculate the voltage drop as.

Also, 3% voltage drop is allowable. EV’s are not going to have a problem with a lower voltage as long as it is not such a swing on voltage between the starting voltage and the voltage under load that the car stops charging due to it thinking there is something wrong.

this table is for building wiring, not extension cords. This table is more applicable: http://www.cmewire.com/catalog/sec19-fcx/fcx-cu-01-amp.pdf

Since the charger will only draw 24 amps, you can use 12 AWG SOOW cord. However, I would consider moving up to 8 AWG if the cord had any length to it, to limit voltage drop. Once you’re past the plug, the cord is sized for the device, not the circuit itself. For example, a lamp can be plugged in to a 20 amp circuit, but likely uses 18 gauge wire, which is enough for the lamp, but not a full 20 amps.
 

eprosenx

Active Member
May 30, 2018
2,065
2,483
Beaverton, OR
this table is for building wiring, not extension cords. This table is more applicable: http://www.cmewire.com/catalog/sec19-fcx/fcx-cu-01-amp.pdf

Since the charger will only draw 24 amps, you can use 12 AWG SOOW cord. However, I would consider moving up to 8 AWG if the cord had any length to it, to limit voltage drop. Once you’re past the plug, the cord is sized for the device, not the circuit itself. For example, a lamp can be plugged in to a 20 amp circuit, but likely uses 18 gauge wire, which is enough for the lamp, but not a full 20 amps.

So while technically cord like SOOW may be good for 24 amps (barely) as 12 AWG, I suspect UL would not be ok with this (I don't know the UL regs as well as I know NEC). If it is anything like NEC, they require continuous loads to have conductor sizing at 125% of the expected draw. Beyond that, I don't think it would ever be a good idea to build an extension cord with less ampacity than the receptacles it plugs into since someone may use that cord for some load other than an EV that might need the full 30 amps (non-continuous).

10 AWG is definitely the standard size for a 30a circuit. As @ivy_ mentions, if you have a long run or specifically care about voltage drop you could move up a size to 8 AWG, but for 40' I would likely not.

If we were talking about using SOOW cord as a hardwired line set into some device, then yes, you could potentially size it smaller than the circuit size (as in your lamp example).
 

gilscales

Active Member
Jul 16, 2016
1,684
1,899
Long Beach, CA
hi all. I have a 14-30 outlet in my basement. Unfortunately it is 40 ft from where the new M3+ will be parked in our carport. I am having trouble sourcing a cord up here in BC. The L14-30 cords are available but I believe these are for generators. My question is can I use the L14-30 cord to charge the car? I have ordered the Tesla 13-30 adapter. Thanks in advance.
The reasons for not using an extension cord, 1. you will not have gfci protection for the extension unless you have a gfci breaker on the circuit (not likely) 2. having 24A on a cord without gfci protection means that if someone punctures the insulation and makes contact with the conductor you could have a potential to do severe damage to someones health. 3. just one more weak spot in the connection to fail and an off the shelf extension cord will not have the best quality receptacle and plug.

Why not remove the 14/30 outlet and use this for a junction box then mount a surface box (extension) on top of the outlet box with conduit coming from that with 10 gauge wire to your desired location, I would then recommend a high quality 14/30 outlet such as the Bryant 9430FR Buy Single Straight Blade Receptacles - Free Shipping over $50 | Zoro.com as they are far superior in construction to the big box store units.
 

user212_nr

Active Member
Aug 26, 2019
1,407
737
US
The OP "nole" is long gone. Stop responding to this thread and putting it at the top of the "Battery and Charging" forum.

His last response was 5 days ago that he found what he needed.
 

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