PSA - periodically replace your NEMA 14-50 outlet

[nwdiver]

I wish Tesla would not include the UMC so more folks would consider the Wall Connector, so much more robust in many ways.

What about a wall connector that uses a 14-50

Nothing wrong with a 14-50. A lot of this is just selection bias. HPWCs fail too but that's chalked up to a bad install. Every 'melted' 14-50 is immediately blamed on the 14-50. Sometimes it's a bad install, sometimes it's the UMC, sometimes someone didn't plug it in all the way... etc. etc.

IMO the biggest thing that would help is charging at the current you need instead of always pushing 40 or 32A. If you only need 5kWh and you've got all night... charge at 20A or even 10A. 20A produces 75% less heat than 40A. 10A ~93% less heat.

 

[mswlogo]

If you leave the UMC plugged in all the time

So who is going to enforce that?
Who is going to enforce that for next owner of the home shall leave their UMC plugged in?
Who is going to enforce a child never touches it?

If my wife promises (cross heart heart stick a needle in your eye) to never, ever unplug her GFCI protected hair dryer in the bathroom will the electrical inspector let me skip installing GFCI on the Bathroom outlet? Why not? It's exactly the same suggestion you just made.

The point is, the UMC is portable, it can be unplugged, and will be unplugged. And it might not be the person that had it installed.

 

[mswlogo]

What about a wall connector that uses a 14-50

Nothing wrong with a 14-50. A lot of this is just selection bias. HPWCs fail too but that's chalked up to a bad install. Every 'melted' 14-50 is immediately blamed on the 14-50. Sometimes it's a bad install, sometimes it's the UMC, sometimes someone didn't plug it in all the way... etc. etc.

IMO the biggest thing that would help is charging at the current you need instead of always pushing 40 or 32A. If you only need 5kWh and you've got all night... charge at 20A or even 10A. 20A produces 75% less heat than 40A. 10A ~93% less heat.

We were talking about protecting from being electrocuted via the code requirement for a GFCI on 14-50 outlets. But sure, anything can fail and cause other problems too. 14-50 outlets are a common culprit of failures you even stated a great example, they didn't plug in all the way, lost it's tension, corroded. etc. And yeah the 14-50 could be overloaded and being the weakest link is likely to melt first.

It's been shown that higher currents generally charge more efficiently (to a point). Partly because the longer you charge the longer the car doesn't sleep (which uses power). And in really cold temps the heating of the battery can take a very long time at lower currents and is sometimes still being exposed to cold weather (your fighting heat losses) so it's just chasing it's tail at low current. On a high current circuit it can get the battery warmed up quickly and switch to 100% charging more efficiently (shorter heating period less heat loss). Higher current might also keep or raise the battery to a better temperature for more efficient charging as well. And when using departure time charging you could have a warmer battery (with higher current over a shorter time closer to departure) for better regen.

Charge Efficiency Chart From Our Model 3

Looks like Tesla no longer offers the 14-50 corded Wall Connector, again.

 

[nwdiver]

We were talking about protecting from being electrocuted via the code requirement for a GFCI on 14-50 outlets.

If a GFCI is required for a 14-50 outlet then every RV park I've been to is in violation.

In terms of the charge efficiency at different charge rates those numbers were collected at the car and didn't include line losses. I agree it's plausible that a VERY low rate of 5 maybe even 10A could be counter productive but it's unlikely 20A would be worse once line losses are accounted for. If you have a ~50' run plus another 20' of EVSE cable there's a ~1% reduction in total energy loss from 40A to 20A. There are a lot of variables involved. I agree charging at ~40A+ may be beneficial when it's cold.


Maybe I'll attempt to test this...

 

[mswlogo]

If a GFCI is required for a 14-50 outlet then every RV park I've been to is in violation.

In terms of the charge efficiency at different charge rates those numbers were collected at the car and didn't include line losses. I agree it's plausible that a VERY low rate of 5 maybe even 10A could be counter productive but it's unlikely 20A would be worse once line losses are accounted for. If you have a ~50' run plus another 20' of EVSE cable there's a ~1% reduction in total energy loss from 40A to 20A. There are a lot of variables involved. I agree charging at ~40A+ may be beneficial when it's cold.

Maybe I'll attempt to test this...

RV’s are being argued here. I don’t own an RV park. If I did and it was before the new code requires it, I’d have GFCI on the 14-50 for liability reasons. I’m sure folks could be tired, dark and wet when plugging in and a recipe for accidents. Possibly even plugging in after a few beers.

- Mike Holt's Forum

You make a valid point that the chart is at the car only. But the car itself does prefer it.

I suspect you are confusing the cost of line loss at different amps. Going from 20A to 40A doubles whatever your loss is, in Watts. But going from 20A to 40A cuts the run time in half (or better, because the car prefers it). So your loss in kWh remains the same (or better).

if your wires are cooking at rated amps, efficiency is not your primary problem.

 

[kkillebrew]

A GFCI is built into the UMC but that can’t protect the exposed outlet.

Does a hair dryer with GFCI on the cord exclude you from needing a GFCI in your bathroom outlet, If you promise to only use the hair dryer? You’re suggesting exactly the same thing.

Yes I am, I was assuming if you are having a 50 amp circuit installed for a car charger it is for a dedicated purpose except for the few times he needs to uplnug the mobil charger. You said yourself it can, and does cause problems. There are many posts to this example. I am not suggesting that anyone be unsafe. A hair dryer is quite a different thing in all ways and is not a good example, but I concede your point.

 

[ucmndd]

You make a valid point that the chart is at the car only. But the car itself does prefer it.

I suspect you are confusing the cost of line loss at different amps. Going from 20A to 40A doubles whatever your loss is, in Watts. But going from 20A to 40A cuts the run time in half (or better, because the car prefers it).

What is leading you to believe the car “prefers” to charge at higher amperage?

As for efficiency, it’s been shown a couple different times that the highest efficiency tends to be at the multiples of the individual charger boards in the car.

Early S/X with one or two 40 amp chargers were most efficient at ~40 or 80 amps.

The next gen with either two or three 24A charging boards have efficiency peaks at 24, 48, or 72 amps.

I haven’t seen anyone measure/confirm, but I suspect the current gen S/X and Model 3 chargers are most efficient at multiples of 16 - 16, 32, or 48 amps.

 

[ucmndd]

@mswlogo is there something specific about my question to you or the objective work of others (which you can find in this forum section) that you “disagree” with?

 

[cduzz]

What about a wall connector that uses a 14-50

Nothing wrong with a 14-50. A lot of this is just selection bias. HPWCs fail too but that's chalked up to a bad install. Every 'melted' 14-50 is immediately blamed on the 14-50. Sometimes it's a bad install, sometimes it's the UMC, sometimes someone didn't plug it in all the way... etc. etc.

IMO the biggest thing that would help is charging at the current you need instead of always pushing 40 or 32A. If you only need 5kWh and you've got all night... charge at 20A or even 10A. 20A produces 75% less heat than 40A. 10A ~93% less heat.

It is clear to me and should be clear to anyone that adding a 14-50 or any other plug in the mix makes the circuit less reliable and less safe.

A fixed charger is obviously safer. The question is "how much safer?" and "is that added margin of safety worth the money to buy a dedicated charger?"

Your options for charging your car are:

• Never charge at home
• use an existing plug and your existing adapter (let's assume you've got a 14-50 in your garage from when the prior owner of your garage was a welder or had a drill press)
  • plug / un-plug constantly as you need your charger in the car or connected to the plug to charge
  • buy a 2nd mobile charger
  • leave mobile charger plugged in and don't have it in the car
• use an existing plug and you buy an adapter for your mobile charger
  • plug / un-plug constantly as you need your charger in the car or connected to the plug to charge
  • buy a 2nd mobile charger
  • leave mobile charger plugged in and don't have it in the car
• convert existing plug to use hard-wired charger
• add entirely new circuit
  • use nema 14-50 or similar, go to "use an existing plug"
  • have circuit hard-wired to connect to a dedicated charger

I think I'd say that the above is ranked from least to most expensive.

We will have a good gauge for how dangerous it is to use plugs when insurance companies start treating non-permanently installed charger setups the same way the treat aluminum wires or knob and post wiring. If insurance companies start asking "do you have an electric car? Do you charge it at home? Do you use a dedicated fixed charger or does your charger have a plug?" a bell should go off in your head saying "geez, enough incidents have happened that perhaps it isn't as safe as I thought."

I personally have an outdoor nema 6-20 plug that runs on a dedicated circuit that was originally for a 120 circuit that has 12 gauge wires; I had an electrician convert it to be a no-neutral 240v circuit and I use an adapter for my gen-1 mobile charger so I am plugging and unplugging the cord whenever I use it. I have plugged it in in the rain and it didn't kill me. I also charge at home once per month. I did not buy a fixed charger at first because I wasn't comfortable that such a dinky circuit would be good enough for my uses. I didn't want to get a bigger circuit because adding one would be opening a giant can of worms -- need new panel, new feed from utility, new meter, etc.

Turns out that after some experimenting in this latest cold snap, it is sufficient to warm a cold soaked battery after only 2 hours, so I can safely call it "good enough" and after I scrape together enough money I'll convert the outdoor outlet to a junction box and install a hardwired charger like the tesla wall charger or a clippercreek lcs20.

In the meantime, mostly, I just charge charge at work.

As far as RVs go -- how many of those draw 40a continuously for 6 hours at a shot?

 

[nwdiver]

As far as RVs go -- how many of those draw 40a continuously for 6 hours at a shot?

As far as GFCIs go the average current draw is irrelevant to the question.

I've charged at several RV parks and I've never had an issue aside from the car lowing the amperage to 30A due to voltage droop. Like I said... a lot of the issues with 14-50s are selection bias. I had a solar inverter melt a wire because of a loose termination... had that been a 14-50 it could have ended up on the forums as another cautionary tale of why hard-wired is so much better.

I setup a charger for my Mom when she got her Model 3. I chose to use a HPWC with a 14-50 to give her the flexibility of using her UMC if there was a problem with the HPWC. I also told her to limit her charge rate to ~20A unless there was a reason she needs to charge faster.


I like your NEMA 6-20 solution. IMO that's really one of the best ways to go.

 

[DarkMatter]

How often do people actually carry the UMC with them? I only do when I'm going somewhere out of town with an AirBNB where I will charge, or the airport, or similar. Before that it lived plugged in until I installed a Wall Connector.

 

[eevee-fan]

My neighbor has a Model S, I told him to charge at the lowest amp he needs to get it topped up daily.

Calculate from when you plug in to charge to when you need the car charged by... set the charge rate on the car appropriately.

And your power company would love you for it, if they weren't so evil in the first place. haha

Low current draw = low amp = loss risk of fire. Win-Win-Win!

I own a Bolt EV, it came with a 12A EVSE that sticker says is good for 120v but it's actually 120/240v. Anyway, my NEMA 14-50R with #6 wiring inside the walls only handles 12A out of 50A max/40A continuous... runs nice and cool!

 

[nwdiver]

My neighbor has a Model S, I told him to charge at the lowest amp he needs to get it topped up daily.

Calculate from when you plug in to charge to when you need the car charged by... set the charge rate on the car appropriately.

Low current draw = low amp = loss risk of fire. Win-Win-Win!

I do agree with some of the previous statements that there is a limit to the positives of low amp charging... especially if it's cold. But I think anything >10A should be fine.

 

[brucet999]

If a GFCI is required for a 14-50 outlet then every RV park I've been to is in violation.

Maybe I'll attempt to test this...

Without looking inside their distribution panel, how would you know whether or not an RV park 14-50 outlet circuit is GFCI protected?

 

[JPoldo]

So who is going to enforce that?
Who is going to enforce that for next owner of the home shall leave their UMC plugged in?
Who is going to enforce a child never touches it?

Mswlogo, you make very valid points. Guess I was only thinking of my specific situation where I'm the only person who touches the NEMA outlet and there are no children. Selfishly, there was no consideration for the next home owner. Fortunately, my electrical box, wall plate, and conduit are all plastic so doubt anyone could get a ground fault shock. When installing the next 14-50, I'll spend $50 additional for the GFCI.

 

[mswlogo]

Mswlogo, you make very valid points. Guess I was only thinking of my specific situation where I'm the only person who touches the NEMA outlet and there are no children. Selfishly, there was no consideration for the next home owner. Fortunately, my electrical box, wall plate, and conduit are all plastic so doubt anyone could get a ground fault shock. When installing the next 14-50, I'll spend $50 additional for the GFCI.

I’m just stating what the new code is. You can choose what ever you choose to do. But You clearly do not understand how one does get electrocuted by your comments. Good luck.

 

[nwdiver]

Without looking inside their distribution panel, how would you know whether or not an RV park 14-50 outlet circuit is GFCI protected?

.... have you never been to an RV park? Where you plug in usually IS the distribution panel. The breaker is almost always right above the plug.

 

[ucmndd]

@mswlogo is there something specific about my question to you or the objective work of others (which you can find in this forum section) that you “disagree” with?

@mswlogo I guess we’ll go with “no” then?

 

[brucet999]

.... have you never been to an RV park? Where you plug in usually IS the distribution panel. The breaker is almost always right above the plug.

No, I haven't, but I have never noticed a distribution panel (usually at or including the meter and distributing power to several circuits, although it could be a sub panel) in a public facility that allows access by the public to the breakers. Usually a service panel is either inside a locked equipment room or at least its cover is padlocked to prevent unauthorized access.

 

[tga]

No, I haven't, but I have never noticed a distribution panel (usually at or including the meter and distributing power to several circuits, although it could be a sub panel) in a public facility that allows access by the public to the breakers. Usually a service panel is either inside a locked equipment room or at least its cover is padlocked to prevent unauthorized access.

RV parks generally have one of these at every (50A) space. There is a similar version without the 14-50 (just the TT-30 and 5-20). There are independent breakers for each outlet at the space.