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Convert NEMA 5-20 to 6-20?

ratsbew

Active Member
Mar 3, 2012
1,122
3
O'Fallon, IL
KBgpRt2.png


Charge rate on NEMA 6-20 on my Model 3.
 
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SSedan

Active Member
Jul 24, 2017
2,948
0
Greenville Wisconsin
I think this is good info but just want to add a qualifier about cold temps. I am sure this works well most of the year most of the country but temp starts dropping below freezing and it is unlikely to work well. Not sure of M3 amperage draw for battery heating but tonight at 37f my S was pulling 15amps at 240volts just to warm the cabin when I sat down to run nav routes.
In the dead of winter 10f and lower with a 30amp outlet battery/interior warmup could consume a few miles.
 
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eprosenx

Active Member
May 30, 2018
2,064
0
Beaverton, OR
So 6-20 charge should be around double the charging rate of a 5-20?

Correct (when on 240v residential service). And actually a faster charge than double since there are fixed overhead losses while charging (cooling pumps, etc) and so any boost in energy input goes direct to the battery since fixed losses are already covered.
 
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davewill

Active Member
Feb 5, 2014
1,802
0
San Diego, CA, US
So 6-20 charge should be around double the charging rate of a 5-20?
Actually a little more because charging has a fixed overhead of 3-400W or so:

5-15: 12a * 120v = 1440W - 300W = 1140W net charge rate
5-20: 16a * 120v = 1920W - 300W = 1620W
6-20: 16a * 240v = 3840W - 300W = 3640W

As you can see with a conservative overhead (I think the overhead might be bigger), the 6-20 is over triple the speed of a 5-15, and 2.25 times a 5-20. Any extra overhead (like from cold weather) will make this even more pronounced.
 

jgs

Active Member
Oct 28, 2014
1,581
0
Ann Arbor, Michigan
I think this is good info but just want to add a qualifier about cold temps. I am sure this works well most of the year most of the country but temp starts dropping below freezing and it is unlikely to work well. Not sure of M3 amperage draw for battery heating but tonight at 37f my S was pulling 15amps at 240volts just to warm the cabin when I sat down to run nav routes.
In the dead of winter 10f and lower with a 30amp outlet battery/interior warmup could consume a few miles.
As long as you don't run the cabin heater while the car is parked overnight to charge (who would do that?) it should be just fine. Last winter I had to charge my S on a mere household plug for a few weeks. It was well below freezing the whole time, car outdoors, not in a garage, and I didn't have a problem getting the expected 3 mph or so of charge. I think the 6-20 solution sounds just great.
 

vickh

Active Member
Dec 16, 2018
3,056
0
az
I've been digging in studying and it really looks as simple as swapping the neutral for the other phase (black and white hot wires) which requires a new 240V gang breaker.

Total bill of materials should be under $20 and will allow 15 miles/hour of charging.

so you did'nt have to replace any wiring to panel? just buy breaker and socket? Seems like the best bang/buck
 
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nwdiver

Well-Known Member
Feb 17, 2013
7,361
19
United States
so you did'nt have to replace any wiring to panel? just buy breaker and socket?

Correct. 6-20 and 5-20 each use 3 wires. To upgrade a 5-20 to 6-20 you're repurposing the neutral as a hot you just need to ensure that there are no other outlets on that circuit. I'm a little surprised this doesn't happen more often since it's by far the most cost effective solution to charging at home. You're increasing your charge rate 2.6x and increasing charge efficiency >5%.
 
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davewill

Active Member
Feb 5, 2014
1,802
0
San Diego, CA, US
so you did'nt have to replace any wiring to panel? just buy breaker and socket?

Yes, it can be that easy if you have a 15a or 20a 120v circuit that has a single outlet on it (or can be rewired to have only one outlet). Unfortunately, that situation isn't very common. It mainly happens when an outlet was installed for a specific purpose like an AC or water heater.
 
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ratsbew

Active Member
Mar 3, 2012
1,122
3
O'Fallon, IL
OP here. This 6-20 setup has been amazing for me. Almost 14 months and I've never needed faster charge rate. The only benefit for me would be since I'm on a time-of-use plan and I could gain more miles during the absolute cheapest hours of the day if I had a HPWC...but it would never pay for itself since I only spent $15.00 for this.

According to TeslaFi, I've pulled 3,984kWh through this outlet.
 

Watts_Up

Active Member
Mar 4, 2019
3,092
0
In a galaxy far, far away
What all is required to convert a NEMA 5-20 outlet to a 6-20?

I have a 5-20 in my garage (just discovered it under a wall plate....score!!!) that is in the perfect spot for my UMC.
I looked at your video, but I would be interested to see also your breaker panel.
I am just curious how many 15 A, 20 A, ... breakers do you have.
In particular, I wonder if you might have at least two 20 A breakers?

In general those 20 A plugs are dedicated for kitchen appliances, such as Fridge, Garbage disposal, microwave, toasters...
Also if you are in a house where the dryer uses natural gas, this dryer might have instead a 120 V 15 A or 20 A plug.

I was thinking then, while visiting some relatives or living in a rental place where you don't want to make any electrical circuit changes.
If you can localise two 20 A plugs not caonnected to the same phase, and if there is only ONE plug connected to this circuit,
then it would be interesting to make a kind of "Dryer Buddy" but I call it "Appliance Buddy" in this case to provides 240 V 20 A plug.

The point is that if at any momemt an appliance starts, such as a fridge, the "Appliance Buddy" would stop the EV charger.
This is a little bit like combining two "Dryer Buddy" to make one "Appliance Buddy" to have a NEMA 6-20 without making any electrical changes.
 
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vickh

Active Member
Dec 16, 2018
3,056
0
az
Yes, it can be that easy if you have a 15a or 20a 120v circuit that has a single outlet on it (or can be rewired to have only one outlet). Unfortunately, that situation isn't very common. It mainly happens when an outlet was installed for a specific purpose like an AC or water heater.

or a water softener here in AZ. I have an unused wall plate that I will have an electrician check out and install
 

Watts_Up

Active Member
Mar 4, 2019
3,092
0
In a galaxy far, far away
Yes, it can be that easy if you have a 15a or 20a 120v circuit that has a single outlet on it (or can be rewired to have only one outlet).
Unfortunately, that situation isn't very common.
It mainly happens when an outlet was installed for a specific purpose like an AC or water heater.
This why I would be interested to see the picture of the main panel from theOP.

I noticed in few older built home, that there was a tandem 30 A for an oven range, several 15 A for the rooms, and two 20 A for the kitchen.

If the kitchen is not too far from the garage, you could easily share the two 20 A plugs (if they are not on the same phase)
using some extension cords and an automatic disconnect like used for making a Buddy Dryer.
 
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wws

Member
Aug 11, 2014
855
0
Northern California
This why I would be interested to see the picture of the main panel from theOP.

I noticed in few older built home, that there was a tandem 30 A for an oven range, several 15 A for the rooms, and two 20 A for the kitchen.

If the kitchen is not too far from the garage, you could easily share the two 20 A plugs (if they are not on the same phase)
using some extension cords and an automatic disconnect like used for making a Buddy Dryer.

It is fairly dangerous to do what you are thinking of in homemade fashion. However there is already a device called a "Quick 220". It has the necessary circuitry (e.g., several relays) for relatively safe operation. But won't work on GFCI-protected circuits.
 
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M3BlueGeorgia

Active Member
Dec 10, 2018
1,319
1
Atlanta, GA
I'm going through this now (a bit more work; I'm running dedicated 12 gauge from the panel). Did you just buy Tesla's 6-20 adapter from their site for the mobile charger?

12 gauge will work for 5-20 (120v-20A) but not for 6-20 (240v-20A).
You are going to be pulling twice as many watts, so go with thicker wire. At least 10 gauge.
 

Kirby64

Member
Jun 28, 2018
485
0
Austin, TX
12 gauge will work for 5-20 (120v-20A) but not for 6-20 (240v-20A).
You are going to be pulling twice as many watts, so go with thicker wire. At least 10 gauge.

What are you talking about? The amount of current is the same, so heat wasted in wire losses is the same. 12 gauge wire is 100% acceptable (and code compliant) for a NEMA 6-20 outlet. You need 10 gauge if you want to move up to a 30 amp outlet.
 

gfunkdave

Member
Aug 10, 2016
120
0
Portland, ME
Correct, wire gauge required is a function of the amperage on the circuit. Voltage is irrelevant.

Where voltage becomes a concern is in the insulation on the wire, but all THHN or Romex is rated to much more than standard household voltages. I usually see a 600V rating.

A handy way to think about it is like water going through a pipe. You need a thicker pipe to accommodate more gallons per minute but it doesn't matter if you are expecting 100 gpm at 5 psi or 5000 psi. What does matter in that case is the thickness of the pipe material.
 
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M3BlueGeorgia

Active Member
Dec 10, 2018
1,319
1
Atlanta, GA
12 gauge will work for 5-20 (120v-20A) but not for 6-20 (240v-20A).
You are going to be pulling twice as many watts, so go with thicker wire. At least 10 gauge.

The equations are a bit more complex that this, because it depends on the wire run length.

However, 10 gauge will have less electric loss than 12 gauge, and for anything but a short cable run, it may start to heat up at 240v-20a (240v-16A continuous) whereas it wouldn't at 120v-20a.