7 ms·

Don't use a $5 range outlet for EV charging

21 points by arantius 2y ago

eternityforest 2y ago
What makes a continuous load outlet so expensive? If they were mass produced couldn't they be pretty much the same price?
Analemma_ 2y ago
Does this distinction also apply at the lower amps of ordinary 12V plugs? I frequently trickle-charge my EV from an ordinary 12V outlet outside on the porch for 14 hours or more, is that going to be a problem? (EDIT: sorry, yes, I meant 120V outlet)
- darknavi 2y ago
  I assume you mean 120v outlet, but IMO yes. One good test that I saw somewhere that I do on new outlets I am charging on, is leave the car charging for ~30 minutes and then quickly unplug the charger from the wall. Touch the prongs to your hands. If they are very warm or hot, you are likely over-drawing that outlet and need to ramp down your amperage draw (or better yet, find a new outlet). This article focuses on outlets but the wiring is just as (or more) important and outlets can very easily be installed with under-code wiring.
- abakker 2y ago
  Yes - likely moreso. (I'm assuming you meant 120v plugs, like US residential.) The issue in the circuit ampacity for standard residential outlets - typically, a 120v 15 amp plug will be wired in 14 gauge NM-B wire (romex), which already de-rates the maximum temperature the wire jacketing is allowed to reach over higher ampacity wire (THHN) which is typically run in conduit. For a given wire gauge, THHN has more ampacity and the jacket is rated to a higher temperature. for a 20amp 120v circuit (not common unless you install intentionally for that purpose) you need 12 gauge wire. But, as mentioned in the article, continuous loads need to be up-sized because of temperature, and even standard outlets for the correct ampacity circuit don't often anticipate 100% duty cycle. BUT, the real question is for your trickle charger, how many amps does it draw? if it tries to draw 12 amps on a 15amp circuit, everything is fine. If it tries to draw 15-20 amps on a 15 amp circuit, there is some danger. Many breakers (esp older ones) will not actually pop if the amp demand ramps up slowly. Ampacity Charts: https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/ https://www.cerrowire.com/products/resources/tables-calculat... Source: I've wired a LOT of power tools with big loads, but I am not an electrician. Take this advise as indicative and decide whether it warrants you contacting an electrician to validate your situation.
  - bryanlarsen 2y ago
    Car chargers only pull 12A from a 15A circuit.
    - abakker 2y ago
      Yeah - you'll see that I mentioned that - if that is true, then great. But, IMO, it's worth verifying. Even more worth double checking if the building is old, or an extension cord is involved.
      - bryanlarsen 2y ago
        Yes, the one time I used an extension cord to charge the car, I set the max amperage to 8 even though it was a 15Amp rated cord.
      - LUmBULtERA 2y ago
        It's definitely true on a Tesla using their mobile charger. The car will report on its screen exactly what it's charging at. When I charged at 120v (before getting a hardwire charger installed), the car reported charging at 12 amps.
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doe_eyes 2y ago
I hope I'm not too jaded, but this reads really weird to me. The author disses a "$5 range outlet" (even though I don't think they're usually that cheap), then talks about spending several hundred bucks on better outlets for "evaluation"... and the evaluation never comes. We just get a paragraph of innuendo without any real-world testing or even a thorough teardown. Do the plugs have any real-world design flaws, or is this just gear snobbery? Can the author show that they're heating up too much? Given that there must be hundreds of thousands of home chargers, what's the incidence of problems caused by cheap 240 V plugs?
- bryanlarsen 2y ago
  It's not hard to find pictures online of melted NEMA 14-50 outlets. Design flaw or loose connection? Some will definitely be the latter, but all? Who knows? I'd spend the extra $50. Or set your car to only pull 24A from the outlet rather than full speed. Still more than fast enough to full charge overnight.
- BizarroLand 2y ago
  This blog seems to be one person's passion project. They can write whatever they want to in whatever manner they want to. They're not required to weather your scrutiny or to pass your bar exam to be allowed to post whatever they want. Aside from that, you raise good points, but you can very well ask your questions directly to the author using the comment section of their blog, you're somewhat more likely to get a satisfying answer there than here.
- quickthrowman 2y ago
  > Do the plugs have any real-world design flaws, or is this just gear snobbery? Design flaws? No. Limitations, yes. A $5 NEMA 14-50R is designed for maybe a few dozen to a few hundred insertion cycles. They’re typically used for ranges (and other fixed equipment) that are plugged in once, and then unplugged once more when you replace the appliance. When the contacts wear out, gaps appear and arcs occur inside the device and it melts. Internal shorts can also happen inside the device. Here’s a tear down video of a residential NEMA 5-15R and a commercial NEMA 5-15R that illustrates some of the shortcomings of cheap wiring devices and shows how more expensive devices have a more robust design: https://youtu.be/kX6xnOksQTc https://youtu.be/kX6xnOksQTc It could also be caused by not using a torque screwdriver to tighten the terminal screws, which is required by the NEC. You must tighten the terminal screws to the torque value listed in the wiring device instructions, and hold it there for 5 seconds. A loose termination can cause all sorts of nasty problems. There are many grades of wiring devices meant for different applications. More $$ = more durable, better contacts, a full brass strap inside the device, etc. Most people are unaware that multiple grades of wiring devices exist, and also unaware that it can be very important to use the correct one and also install it correctly which requires a torque screwdriver. This is why it’s a good idea to just pay an electrician to do it correctly. Leviton sells a heavy duty NEMA 14-50R specifically designed for plug in EV chargers that are designed to handle many insertion cycles. It costs about $67, but that’s the wiring device you buy if you’re going to be doing a lot of insertion cycles. https://store.leviton.com/products/50-amp-ev-charging-receptacle-outlet-heavy-duty-1450r https://store.leviton.com/products/50-amp-ev-charging-recept... There’s no such thing as a NEMA 14-50R that isn’t rated for a 50A continuous load. It wouldn’t be UL listed if that was the case.
jasonpeacock 2y ago
I need to see evidence of this "overheating and melting the outlet". Electrical code requires downrating of actual capacity to prevent things like this. You're far more likely to see damage due to loose connections - either the wires are not fully secured to the outlet, or the plug is not fully seated & snug, both of which cause overheating.
- Kirby64 2y ago
  Read any EV forum. Plenty of people with melted Leviton 14-50 outlets, despite having fully secure and tightened wires.
  - quickthrowman 2y ago
    Fully secured and tightened isn’t good enough. Per code, you need to use a torque screwdriver (or other approved means) to tighten the terminal screws to the torque value listed in the wiring device instructions. > NEC 110.14 (D) Tightening torque values for terminal connections shall be as indicated on equipment or in installation instructions provided by the manufacturer. An approved means shall be used to achieve the indicated torque value.
    - Kirby64 2y ago
      I can assure you this often has nothing to do with torque. The Leviton outlet lists a torque of 40 inch pounds. You can hand tighten much tighter than that relatively easy with a reasonable screw driver. There’s some instances of undertorqued outlets, sure, but that isn’t the predominant factor here. The crap outlets are the issue.
      - quickthrowman 2y ago
        True, you can easily hand tighten to 40 inch pounds. After looking at some more evidence, I agree that it’s probably just a poorly designed receptacle, probably on par with a residential 5-15R which are made to a much lower standard than a comparable commercial 5-15R. It looks like Leviton may have discontinued the receptacle that lots of people had melt on them so that probably is the case.
CaliforniaKarl 2y ago
> Even though the 14-50R outlet is technically a 50A outlet, when used as a kitchen range plug, they are often wired on a 40A circuit. This is permitted by the Canadian Electrical Code rule 26-744 5). I wonder if the US National Electric Code allows this.
- egberts1 2y ago
  The “50” in 14-50R refers to the maximum "rated" amperage allowed through the receptacle. Load-wise, to avoid melted connector, you don't plug something with load capacity of more than 37-ish ampere thru this 14-50R receptacle. The OP is confusing load rating vs. capacity rating. However, computed loads are always adequately under the breaker size, and beneath wire capacity, and below the receptacle rating, all three and each components of a circuit. Many urban building codes often demand the 14-50R receptacle to match the 6/3 COPPER (not Romex) wire and 50A breaker size, often as a response to mass introduction of EV. NEC 2018/2022 is unchanged about the permissible used of 50A-rated receptacle with smaller 40A breaker but NEC code firmly states that a breaker cannot exceed 8/3 AWG wire rated capacity and many types of 8/3 sheathing barely supports 50A; that's because NEC is all about load-rating, well beneath its rated capacity. Naturally, in light of those NEC "restrictions", if an EV charger calls for a 50A RATED circuit (because charger performs at nominal load operation at 37A-ish, you'll want all three components of the circuit to each carry 50A. This is the part where the former electric stove/range 8/3 wire failed to meet the new EV charger's demand. If the EV charger is rated for 60A but operates nominally at 46A, DO NOT go the 50A installaion route. Go with 60A. Operating your load capacity near its rated capacity is potential meltdown situation, especially if weather turns hot, Hot, HOT! Also for 50A rated EV charger in the high-temperature area (garage), 8 AWG copper wire and 6 AWG aluminum wire are not NEC-code recommended despite having the 50 AMP to 60 AMP ampacity rating (NEC code); go with 6/3 copper. For most residential garage having 50A-rated EV charger, that means 6/3 (non-Romex) copper AWG, 50A breaker, and 14-50R receptacle. Open-air carport and year-round cooler weather region can NEC-wise get away with (but local/urban electrical code may prevent) the use of 8/3 AWG copper (but no aluminum) wires.
  - Kirby64 2y ago
ldbooth 2y ago
I worked at an EV charger manufacturer. This is a known issue. The issue is a 240V plug value engineered for non-continuous use for things like cooking and laundry loads (where amperage spikes but levels off at fairly low amps) versus a continuous 7-10 hour load like an EV/EVSE (where you have high amps continuously and lots of resulting heat transfer). It's limited to home EV charging. This is one reason why given the choice between a NEMA plug source or a hard wired source (to circuit in Junction box), I would choose the wired source/circuit connection. The plug manufacturers also know about the melted NEMA connector issue and are designing versions for continuous use at the higher price points mentioned.
- deleted 2y ago
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21 points by arantius 2y ago

What makes a continuous load outlet so expensive? If they were mass produced couldn't they be pretty much the same price?

Analemma_ 2y ago

Does this distinction also apply at the lower amps of ordinary 12V plugs? I frequently trickle-charge my EV from an ordinary 12V outlet outside on the porch for 14 hours or more, is that going to be a problem? (EDIT: sorry, yes, I meant 120V outlet)

darknavi 2y ago
I assume you mean 120v outlet, but IMO yes. One good test that I saw somewhere that I do on new outlets I am charging on, is leave the car charging for ~30 minutes and then quickly unplug the charger from the wall. Touch the prongs to your hands. If they are very warm or hot, you are likely over-drawing that outlet and need to ramp down your amperage draw (or better yet, find a new outlet). This article focuses on outlets but the wiring is just as (or more) important and outlets can very easily be installed with under-code wiring.
abakker 2y ago
Yes - likely moreso. (I'm assuming you meant 120v plugs, like US residential.) The issue in the circuit ampacity for standard residential outlets - typically, a 120v 15 amp plug will be wired in 14 gauge NM-B wire (romex), which already de-rates the maximum temperature the wire jacketing is allowed to reach over higher ampacity wire (THHN) which is typically run in conduit. For a given wire gauge, THHN has more ampacity and the jacket is rated to a higher temperature. for a 20amp 120v circuit (not common unless you install intentionally for that purpose) you need 12 gauge wire. But, as mentioned in the article, continuous loads need to be up-sized because of temperature, and even standard outlets for the correct ampacity circuit don't often anticipate 100% duty cycle. BUT, the real question is for your trickle charger, how many amps does it draw? if it tries to draw 12 amps on a 15amp circuit, everything is fine. If it tries to draw 15-20 amps on a 15 amp circuit, there is some danger. Many breakers (esp older ones) will not actually pop if the amp demand ramps up slowly. Ampacity Charts: https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/ https://www.cerrowire.com/products/resources/tables-calculat... Source: I've wired a LOT of power tools with big loads, but I am not an electrician. Take this advise as indicative and decide whether it warrants you contacting an electrician to validate your situation.
- bryanlarsen 2y ago
  Car chargers only pull 12A from a 15A circuit.
  - abakker 2y ago
    Yeah - you'll see that I mentioned that - if that is true, then great. But, IMO, it's worth verifying. Even more worth double checking if the building is old, or an extension cord is involved.
    - bryanlarsen 2y ago
      Yes, the one time I used an extension cord to charge the car, I set the max amperage to 8 even though it was a 15Amp rated cord.
    - LUmBULtERA 2y ago
      It's definitely true on a Tesla using their mobile charger. The car will report on its screen exactly what it's charging at. When I charged at 120v (before getting a hardwire charger installed), the car reported charging at 12 amps.

deleted 2y ago

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doe_eyes 2y ago

I hope I'm not too jaded, but this reads really weird to me. The author disses a "$5 range outlet" (even though I don't think they're usually that cheap), then talks about spending several hundred bucks on better outlets for "evaluation"... and the evaluation never comes. We just get a paragraph of innuendo without any real-world testing or even a thorough teardown. Do the plugs have any real-world design flaws, or is this just gear snobbery? Can the author show that they're heating up too much? Given that there must be hundreds of thousands of home chargers, what's the incidence of problems caused by cheap 240 V plugs?

bryanlarsen 2y ago
It's not hard to find pictures online of melted NEMA 14-50 outlets. Design flaw or loose connection? Some will definitely be the latter, but all? Who knows? I'd spend the extra $50. Or set your car to only pull 24A from the outlet rather than full speed. Still more than fast enough to full charge overnight.
BizarroLand 2y ago
This blog seems to be one person's passion project. They can write whatever they want to in whatever manner they want to. They're not required to weather your scrutiny or to pass your bar exam to be allowed to post whatever they want. Aside from that, you raise good points, but you can very well ask your questions directly to the author using the comment section of their blog, you're somewhat more likely to get a satisfying answer there than here.
quickthrowman 2y ago
> Do the plugs have any real-world design flaws, or is this just gear snobbery? Design flaws? No. Limitations, yes. A $5 NEMA 14-50R is designed for maybe a few dozen to a few hundred insertion cycles. They’re typically used for ranges (and other fixed equipment) that are plugged in once, and then unplugged once more when you replace the appliance. When the contacts wear out, gaps appear and arcs occur inside the device and it melts. Internal shorts can also happen inside the device. Here’s a tear down video of a residential NEMA 5-15R and a commercial NEMA 5-15R that illustrates some of the shortcomings of cheap wiring devices and shows how more expensive devices have a more robust design: https://youtu.be/kX6xnOksQTc https://youtu.be/kX6xnOksQTc It could also be caused by not using a torque screwdriver to tighten the terminal screws, which is required by the NEC. You must tighten the terminal screws to the torque value listed in the wiring device instructions, and hold it there for 5 seconds. A loose termination can cause all sorts of nasty problems. There are many grades of wiring devices meant for different applications. More $$ = more durable, better contacts, a full brass strap inside the device, etc. Most people are unaware that multiple grades of wiring devices exist, and also unaware that it can be very important to use the correct one and also install it correctly which requires a torque screwdriver. This is why it’s a good idea to just pay an electrician to do it correctly. Leviton sells a heavy duty NEMA 14-50R specifically designed for plug in EV chargers that are designed to handle many insertion cycles. It costs about $67, but that’s the wiring device you buy if you’re going to be doing a lot of insertion cycles. https://store.leviton.com/products/50-amp-ev-charging-receptacle-outlet-heavy-duty-1450r https://store.leviton.com/products/50-amp-ev-charging-recept... There’s no such thing as a NEMA 14-50R that isn’t rated for a 50A continuous load. It wouldn’t be UL listed if that was the case.

jasonpeacock 2y ago

I need to see evidence of this "overheating and melting the outlet". Electrical code requires downrating of actual capacity to prevent things like this. You're far more likely to see damage due to loose connections - either the wires are not fully secured to the outlet, or the plug is not fully seated & snug, both of which cause overheating.

Kirby64 2y ago
Read any EV forum. Plenty of people with melted Leviton 14-50 outlets, despite having fully secure and tightened wires.
- quickthrowman 2y ago
  Fully secured and tightened isn’t good enough. Per code, you need to use a torque screwdriver (or other approved means) to tighten the terminal screws to the torque value listed in the wiring device instructions. > NEC 110.14 (D) Tightening torque values for terminal connections shall be as indicated on equipment or in installation instructions provided by the manufacturer. An approved means shall be used to achieve the indicated torque value.
  - Kirby64 2y ago
    I can assure you this often has nothing to do with torque. The Leviton outlet lists a torque of 40 inch pounds. You can hand tighten much tighter than that relatively easy with a reasonable screw driver. There’s some instances of undertorqued outlets, sure, but that isn’t the predominant factor here. The crap outlets are the issue.
    - quickthrowman 2y ago
      True, you can easily hand tighten to 40 inch pounds. After looking at some more evidence, I agree that it’s probably just a poorly designed receptacle, probably on par with a residential 5-15R which are made to a much lower standard than a comparable commercial 5-15R. It looks like Leviton may have discontinued the receptacle that lots of people had melt on them so that probably is the case.

CaliforniaKarl 2y ago

> Even though the 14-50R outlet is technically a 50A outlet, when used as a kitchen range plug, they are often wired on a 40A circuit. This is permitted by the Canadian Electrical Code rule 26-744 5). I wonder if the US National Electric Code allows this.

egberts1 2y ago
The “50” in 14-50R refers to the maximum "rated" amperage allowed through the receptacle. Load-wise, to avoid melted connector, you don't plug something with load capacity of more than 37-ish ampere thru this 14-50R receptacle. The OP is confusing load rating vs. capacity rating. However, computed loads are always adequately under the breaker size, and beneath wire capacity, and below the receptacle rating, all three and each components of a circuit. Many urban building codes often demand the 14-50R receptacle to match the 6/3 COPPER (not Romex) wire and 50A breaker size, often as a response to mass introduction of EV. NEC 2018/2022 is unchanged about the permissible used of 50A-rated receptacle with smaller 40A breaker but NEC code firmly states that a breaker cannot exceed 8/3 AWG wire rated capacity and many types of 8/3 sheathing barely supports 50A; that's because NEC is all about load-rating, well beneath its rated capacity. Naturally, in light of those NEC "restrictions", if an EV charger calls for a 50A RATED circuit (because charger performs at nominal load operation at 37A-ish, you'll want all three components of the circuit to each carry 50A. This is the part where the former electric stove/range 8/3 wire failed to meet the new EV charger's demand. If the EV charger is rated for 60A but operates nominally at 46A, DO NOT go the 50A installaion route. Go with 60A. Operating your load capacity near its rated capacity is potential meltdown situation, especially if weather turns hot, Hot, HOT! Also for 50A rated EV charger in the high-temperature area (garage), 8 AWG copper wire and 6 AWG aluminum wire are not NEC-code recommended despite having the 50 AMP to 60 AMP ampacity rating (NEC code); go with 6/3 copper. For most residential garage having 50A-rated EV charger, that means 6/3 (non-Romex) copper AWG, 50A breaker, and 14-50R receptacle. Open-air carport and year-round cooler weather region can NEC-wise get away with (but local/urban electrical code may prevent) the use of 8/3 AWG copper (but no aluminum) wires.
- Kirby64 2y ago

ldbooth 2y ago

I worked at an EV charger manufacturer. This is a known issue. The issue is a 240V plug value engineered for non-continuous use for things like cooking and laundry loads (where amperage spikes but levels off at fairly low amps) versus a continuous 7-10 hour load like an EV/EVSE (where you have high amps continuously and lots of resulting heat transfer). It's limited to home EV charging. This is one reason why given the choice between a NEMA plug source or a hard wired source (to circuit in Junction box), I would choose the wired source/circuit connection. The plug manufacturers also know about the melted NEMA connector issue and are designing versions for continuous use at the higher price points mentioned.

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