14-50 vs 14-30 Question

[Rojer Lockless]

Hi guys.

My dryer output is a 14-30 that I'm currently not using for anything. I only have the 14-50 plug for my M3.

My question is can I replace the outlet on the 14-30 even though its only a 30 amp breaker and plug the car in using the 14-50 plug and will the car figure it out and only charge at the reduced amps?

Thanks.

 

[Eno Deb]

My dryer output is a 14-30 that I'm currently not using for anything. I only have the 14-50 plug for my M3.

My question is can I replace the outlet on the 14-30 even though its only a 30 amp breaker and plug the car in using the 14-50 plug and will the car figure it out and only charge at the reduced amps?

No. The 14-50 adapter signals to the car that it's connected to a 50A circuit, so you'd have to rely on manually reducing the current. It's also a code violation. Don't do it. The 14-30 adapter is just $35.

 

[Kirby64]

No. The 14-50 adapter signals to the car that it's connected to a 50A circuit, so you'd have to rely on manually reducing the current. It's also a code violation. Don't do it. The 14-30 adapter is just $35.

+1. The adapter is $35. A new outlet plus breaker plus appropriate wiring is going to be a lot more than $35. If you just replace the outlet, it'll be a lot more than $35... since you'll probably burn down your house.

 

[derotam]

+1. The adapter is $35. A new outlet plus breaker plus appropriate wiring is going to be a lot more than $35. If you just replace the outlet, it'll be a lot more than $35... since you'll probably burn down your house.

Ehh, he shouldn't burn down the house since the 30A breaker *should* trip. Now if it doesn't trip, then yes, burned down house is likely.

 

[Rojer Lockless]

Got ya, that's what I was wondering. I'll just get the adapter. Thank you I don't think it's worth running a 50 amp breaker to the panel ect just for a little faster charge.

 

[Kirby64]

Ehh, he shouldn't burn down the house since the 30A breaker *should* trip. Now if it doesn't trip, then yes, burned down house is likely.

Honestly, it's entirely possible it wouldn't. 32A (what a UMC gen 2 would pull) is within margin for continuous operation (where it wouldn't trip) if certain conditions are right.

Most breakers I've seen have current-time curves that imply they won't trip until 1.2x their rating even after an infinite time, assuming the temperature is right. And that's no good for the wiring...

Here's a 30A GE breaker (first one I found):
https://apps.geindustrial.com/publibrary/checkout/DES-062?TNR=Time Current Curves|DES-062|PDF&filename=DES-062.pdf

Looks like it wouldn't trip until 35A at 40C, which isn't unreasonable in the summer time.

EDIT: Re-reading the current-curve, it actually looks like that should be 32.5A at 40C... still, that wouldn't trip a UMC2.

 

[ewoodrick]

Never, ever replace a socket with a higher current one. Even if the breaker would trip, you are heating the wires beyond normal and will contribute to catastrophic failure, if not today, maybe a year from now
And if the fire Marshall finds this as the cause, your insurance may decide not to pay.

Just get the adapter and sleep well at night

 

[Rojer Lockless]

I was planning on setting the car to 28 amp max. I wasn't going to try and overcharge it just because the plug was a 50 but the wires and breaker were 30.

 

[Big Earl]

I was planning on setting the car to 28 amp max. I wasn't going to try and overcharge it just because the plug was a 50 but the wires and breaker were 30.

A 30 amp breaker should have no more than a 24 amp continuous load. 80% rule.

 

[davewill]

You can also hack off the neutral pin on your 14-50 adapter, then it will plug into 14-30, 14-50 and 14-60. A solution I consider OK for one time use where you can double check that you aren't drawing too much, but not for daily use. Just buy the 14-30 adapter.

 

[Federico]

Can you check the wire gauge of your 14-30 outlet? if is 8 AWG you can change the Breaker/Outlet and use the same wire, but if is 10 AWG, then you should buy the 14-30 adapter.

 

[Rojer Lockless]

Already ordered the 14-30. Thanks guys.

 

[SteveGardner]

I just got a new 240 line (with two ganged 50A breakers and the correct outlet) installed by an electrician, who charged $250 here in Bend, Oregon (where electricians are so much in demand that I had to wait several weeks).

I'd been using a regular 110 line since I got my 3 in late March. Charging time went from 4/hr to 29/hr.

Well worth the investment of $250. Actually, $259 including the 14-50R receptacle (which I order from Amazon in advance).

 

[Merle]

Wiring is usually rated over what the breaker rating is set for, meaning that the breaker is designed to be the weak link in the chain. Flip a breaker too much and you shorten the lifespan so that it will cut out at lower percentages or more quickly.

This occurs in snow country with people who have hot tubs that are nearing the end-of-life due to the motors giving out or low water (pumps and heating elements)

Another weak link is the actual outlet. Often you don’t know what kind of abuse it has gone through (particularly those in high traffic areas) and it can arc/short. You can see this in commercial areas where equipment is plugged in and removed (vacuums or pumps)

A CB designed to trip at 30A can be run constantly at 29A, it doesn’t know anything about percentages and is rated to trip at that number. The wiring jobs are typically also done conservatively with the manufacturer giving a threshold of what it can carry and for how long based upon a temperature range. The job of the breaker is to protect the wiring, and if it doesn’t trip while under the rated amperage, then you’ll be fine. If it doesn’t trip above the rated amperage then you have other problems.

I don’t know anyone who tests breakers periodically in residential locations to ensure that they’re doing their job. Like I said, it shortens their life. This even includes the old Zinsco / GTE-Sylvania setups.

Melted wiring (that I have seen) occurs in two primary spots: at the outlet and at the breaker. I’m actually looking at backtracking a wire in a panel that has insulation damage due to heat and corrosion. It can occur where you kink it as well but most runs are pulled when the framing is done and not bent.

Just my $0.02

 

[Rownolds]

Code clarification: The breaker has to be sized for the LOWEST rating of any wire or device in the circuit (exception: 15 amp outlets on a 20 amp circuit, since you can't plug in a 20 amp appliance to a 15 amp outlet). So this means that yes, you can put a 14-50 outlet on a circuit that is protected by a 30 amp breaker. Just like you can run 6 gauge wire to a 20 amp outlet it's OK by code, but you have to have no more than a 20 amp breaker protecting the circuit. Also, code says that if you are going to draw continuously for 3 hours or more you have to de-rate by 20%. So even if everything in the circuit is rated for 30 amps, you can't draw more than 24 amps, by code, for more than 3 hours. So set your car to charge at 24 amps at that location. If you want 30 amps and the car will be charged at that rate in less than 3 hours, it's OK to bump the charge rate up to 30 amps. There's nothing stopping you from drawing 30 amps for 10 hours straight since code doesn't make you put in a 24 amp breaker, but you'd still be violating code.

 

[NoMoreBMWs]

I just got a new 240 line (with two ganged 50A breakers and the correct outlet) installed by an electrician, who charged $250 here in Bend, Oregon (where electricians are so much in demand that I had to wait several weeks).

I'd been using a regular 110 line since I got my 3 in late March. Charging time went from 4/hr to 29/hr.

Well worth the investment of $250. Actually, $259 including the 14-50R receptacle (which I order from Amazon in advance).

You should be getting a higher charging rate at 50a, some where close to 40/hr rather than 29/hr which is typical of a 40a circuit.

 

[ItsNotAboutTheMoney]

You can also hack off the neutral pin on your 14-50 adapter, then it will plug into 14-30, 14-50 and 14-60. A solution I consider OK for one time use where you can double check that you aren't drawing too much, but not for daily use. Just buy the 14-30 adapter.

The adapters are current-limited and should be used appropriately. It shouldn't be hacked to plug into any 30A circuit.

(Part of the issue with the 14-50 adapter is that there's no separate 40A socket definition, so a 14-50 socket might be on a 40A breaker and the safe thing for Tesla to do is limit it to 32A.)

 

[RaeW]

Code clarification: The breaker has to be sized for the LOWEST rating of any wire or device in the circuit (exception: 15 amp outlets on a 20 amp circuit, since you can't plug in a 20 amp appliance to a 15 amp outlet). So this means that yes, you can put a 14-50 outlet on a circuit that is protected by a 30 amp breaker. Just like you can run 6 gauge wire to a 20 amp outlet it's OK by code, but you have to have no more than a 20 amp breaker protecting the circuit. Also, code says that if you are going to draw continuously for 3 hours or more you have to de-rate by 20%. So even if everything in the circuit is rated for 30 amps, you can't draw more than 24 amps, by code, for more than 3 hours. So set your car to charge at 24 amps at that location. If you want 30 amps and the car will be charged at that rate in less than 3 hours, it's OK to bump the charge rate up to 30 amps. There's nothing stopping you from drawing 30 amps for 10 hours straight since code doesn't make you put in a 24 amp breaker, but you'd still be violating code.

Nice to see an intelligent reply rather than the Chicken-Little responses i.e. "burn your house down" and other BS. When I got my MS in 2015 it came with a 14-50 adapter. I installed a 14-50 socket on a 240 V/30 AMP line with 6 gauge wiring. I then set the car to charge at 24 AMPs and put a label on the outlet noting it is 30 AMPs. After three years, in deference to code, I changed the socket to a 14-30.
This makes no practical difference except for code. BTW, the TESLA 14-30 adapter was $45, not $35.

 

[tschmidty]

You should be getting a higher charging rate at 50a, some where close to 40/hr rather than 29/hr which is typical of a 40a circuit.

Er, he is using the Gen 2 mobile charger that has a max rate of 32 amps. HPWC on a 50amp circuit would be 40 amps (37mph for me).

I'd been using a regular 110 line since I got my 3 in late March. Charging time went from 4/hr to 29/hr.

FWIW, you can a wall charger prewired with a 14-50 outlet (or wire it with a 14-50 cord) and plug it in there for 40amps for a whopping 37mph per hour! And actually you can get 40 amps with the old Gen 1 charger which is what I am doing.

 

[TexasEV]

You should be getting a higher charging rate at 50a, some where close to 40/hr rather than 29/hr which is typical of a 40a circuit.

No, because you don’t charge at 50A on a 50A circuit. With the Gen 2 UMC the maximum is 32A charging. That is true whether the NEMA 14-50 outlet is installed on a 50A circuit or on a 40A circuit.