WARNING: Extension Cords

We had a NEMA 14-50 outlet (with GFCI in the circuit breaker) installed in the garage when it was necessary To replace our electric service box (dated from the late 60’s) to “future-proof” the service. After all, soon BEVs and PHEVs will be ubiquitous, right? We got our 2020 Prime (Blue Magnetism rocks) a couple weeks back and realized that, OH Crap, the plug is on the passenger side, and it’ll be a stretch to access our plug unless I back in. Our very first accessory purchase was a 6-foot adapter from Rob43. Problem solved! Thanks, Rob- charging has been flawless.

 

If the Prime is your only EV for a while, I'd recommend switching the breaker to a 20A breaker, if it's something larger right now. That will help protect the wiring in the extension cord and EVSE in the unlikely event of a fault. You don't have to change the breaker to charge the Prime, but if you do it reduces risk. Unfortunately 240V GFCI breakers are not cheap.

Or install a permanent charging station that's designed to plug directly into the 14-50 and leave the breaker at 40 or 50A.

Backing into the garage isn't so bad. It makes pulling out easier!

 

I've been using this extension cord off and on, for about 8 years now, with no issues.
RIDGID 50 ft. 10/3 Heavy-Duty Contractor-Grade Indoor/Outdoor Extension Cord-HD#729-706 - The Home Depot

 

I put white duct tape on the floor to use as a guide while backing it using the backup camera. I like it better that way because now there's no way I'll close the garage door on my open hatch. (I have a low ceiling.) Did that on the PiP and chewed up the spoiler. Not a big deal on the PiP but it would be really bad on the Prime.

 

In California that would not be up to code if there is any 14 AWG wiring inline. I believe 15A circuits are 14 AWG (white Romex) and 20A circuits are 12 AWG (yellow Romex). If you ever tried to sell your house and an astute building inspector figured this out you might have to make it right.

 

If it's a 14-50 outlet, presumably there's no 14 gauge wire in the walls. It would be 6 or 8 gauge on a 40 or 50A breaker.

I'm not completely clear on the details, but I don't think code regulates what you plug into an outlet as much as what's in the walls. For example I can plug in a lamp with 16 gauge wiring or a vacuum cleaner with 17 gauge wire into a 15 or even a 20A circuit. I think the rules for 240V outlets are a little different, since they are not really meant to be general use like 15A or 20A outlets.

So I'm suggesting that if they are going to use the factory EVSE, with it's 5-15p plug, the 40A or 50A breaker should be replaced with 20A. I'm not sure if it's a code requirement, but it's a good idea because the trip current on a 40A breaker can easily melt the 5-15p plug and any wiring in the EVSE.

A reputable EVSE that's sold with a 14-50p plug would be designed to be safe on a 50A circuit, so no breaker change would be needed there.

 

I can't imagine any licensed electric putting 14 AWG on a circuit with a large breaker and NEMA 14-50 outlet.

 

I was commenting on replacing a 15A breaker with a 20A breaker, presumably 110/120V circuit in my reply. Swapping breakers without regard for what is in the wall is what I was referring to.

 

But no one here was suggesting boosting a 15A breaker to 20A. He was talking about dropping the 40A or 50A breaker normally expected on that particular 240V outlet, down to 20A.

If any 14AWG wire was on that 40-50A circuit, then it was far far out of code already. Changing the breaker to 20A doesn't make it any worse at all.

 

Sorry. The thread topic was extension cords and 120V circuits, presumably with L1 charging, and I wasn't paying close attention that subthreads were talking about L2 and 240V circuits. Most of the thread was talking about overloading under-gauged extension cords and the perils of 15A and 20A circuits. Mea culpa.

 

I've used a 12AWG extension cord since I got my Prime. The first thing I did was measure the temperature rise in the plug-end after an hour or two of continuous charging. It was around 8 degrees F, which isn't much.

However, I've been watching that temperature rise increase over the years. I cleaned the blades and switched to another outlet. No change. Eventually, that temperature rise got to 80 degrees F, which is just way, way too much. So I cut the factory end off.

Inside was pure copper wire (good) so I added a decent quality clamp-style plug to the end. The new temperature rise is 4 degrees F, which is basically nothing.

My point is, you have to watch these things. They can degrade with time.

Doing the replacement requires no special skill or tools. You basically need something to cut the wire (I used diagonal cutters), strip the wire (I used my pocket knife), and a phillips screw driver.

 

Wow, that's really bad. Good thing you kept an eye on it.

I wonder if one of us needs to start manufacturing extension cords with a thermal fuse in the plug end? The factory EVSE has a temperature sensor in the plug.

 

Yup! Super easy. But I've discovered that it's often a good idea to go back in a week or so to retorque the clamp screws. You'll probably get another quarter to half turn out of them. I found that true with braided and solid wires when doing installations with all kinds of screw type terminals.

 

I read through this and I think I got the answer to the question I had

I was looking at chargers online and saw one from a company that makes 16A, 32A and 40A (all 240v). They quoted charge times for the Prime and 110v was 3.1Hours, but at 240v it was 2.1 hours, regardless of which charger was used, whereas other vehicles quoted different times for each charger type

I wondered why and figured it was probably because the Prime draws less than 16A when charging. Rob43 said "The standard answer is 12 amps, the real answer is ~11.7 amps" so that's my answer


Model S is 59 hours at 110v !

 

The Prime can draw anywhere from 4A to 16A at any voltage. The stock charge cable (EVSE) that comes with the car is 120V at 12A. The maximum is 240V at 16A. You can set it to 8A and it will drop to 4A on 240V at the end of the charge.

 

I don't know if that statement is correct. I thought PRIME can only charge at 12A using110v. Yeah, if it can get 16A at 110v, then it may finish it at 3.1 hours, but it doesn't AFAIK.

 

It's around 5.5 hours at 12A and 120V.

 

Yes, I know. I use OEM L1 EVSE all the time. I am just wondering about the comment "quoted charge times for the Prime and 110v was 3.1Hours" as stated by @Turquo.

 

It's wrong.