HPWC on 60amp #6?

[Glamisduner]

A few months back when I was at Lowes picking up the wire, they didnt have enough 4 awg for my run. They recommended 2 awg since it was there and they had enough. I said if you can price match, im game. Well now I have my HPWC on an 80 amp breaker and can load share if/when I end up with two Teslas. However, 2 awg wire is a massive pain. But I feel really good when I am charging at 48 amps that I am nowhere near the limit.

You said it man. And here I thougth 4awg was a pain hah! I wonder if I had used 3awg if I would have been able to fit in in my 14-50 outlet I installed before the HPWC. I probably would have needed larger than 1" conduit for 3awg 4 wire run?

 

[Petrlol]

You said it man. And here I thougth 4awg was a pain hah! I wonder if I had used 3awg if I would have been able to fit in in my 14-50 outlet I installed before the HPWC. I probably would have needed larger than 1" conduit for 3awg 4 wire run?

Yeah 3 seems to be the limit in 1" for 3awg.
Conduit fill chart

 

[Sophias_dad]

Yeah 3 seems to be the limit in 1" for 3awg.
Conduit fill chart

Yes, but the ground line can be smaller than the other three.... I'm not sure if it would fit, but it might be worth a look.

In fact, if its a continuous run of metallic conduit, it may be possible to use the conduit itself as the ground. I haven't dealt with conduit myself.

 

[Sophias_dad]

(NEC seems to rate this wire at 95 amps, but from other charts I found 80 is recommended breaker)

That's because the 95 amp rating is usable when the 90 degree celsius rating can be used. To be allowed use the 90 celsius rating, every component and connection in the circuit must be rated to handle 90 degrees celsius. I'm pretty sure that breakers are rated for 75C, and the HPWC manual itself tells you to use the 75C rating in at least one place. 90 degrees celsius is 194 farenheit, plenty hot enough to burn a person. Even 75 is pretty hot.

There's even more adjustments to the ratings, if the expected ambient temperatures are notably higher or lower than the ambient temperatures the wire tables were anticipating. These adjustments are usually pretty small, so unless you are right at the edge(which you shouldn't be designing to), you can probably ignore them.

Also, due to the continuous nature of an EV load, with an 80 amp breaker, you are supposed to only put 64 amps to the vehicle.

 

[SDRick]

Are you guys having any trouble using the back wall entry with the larger gauge wires?

 

[Feathermerchan]

Are you running neutrals? Why? The HPWC and mobile connectors do not use it. Save yourselves some pain and $ by only running two hots and a ground. I bought a Gen 1 mobile connector and Nema 6-50 so I only need to run 6/2 to charge at 40A which is enough even for a larger car than a Model 3 LR. I have also planned for a second 6/2 run if I get a second car.

 

[eprosenx]

Just use 4awg then you don't have to worry. Bonus points if you use 4awg THHN, but sure 6awg THHN in conduit should be ok. Difference in price is negligible though, might as well run 4awg. 6awg Romex however you will need to set the limit to 40 amps. At 40 amps you may was well install a 14-50 and get the newer HPWC so it can be removed more easily.

I'm currently using 4awg THHN with a 60 amp breaker, HPWC set to 48 amps continuous. I can change the breaker to something higher in the future (90 amp) (NEC seems to rate this wire at 95 amps, but from other charts I found 80 is recommended breaker) if I get another car that can charge over 48 amps, I'll swap out the breaker.

I just want to add some color to this apart for future folks googling: 4 AWG Copper Romex (NM cable) is good for a 70a circuit (and equivalent Wall Connector setting). 4 AWG Copper THHN (in conduit) is good for an 80 amp circuit (and equivalent Wall Connector setting). 6 AWG Copper THHN (in conduit) is good for a 60a circuit (and equivalent Wall Connector setting).

Note that the above does not correct for ambient temperatures, more than three current carrying conductors in one conduit, or voltage drop. Though in nearly all installations what I stated above holds true (because you derate for temp adjustments from the actual wire 90c temperature rating, not the artificial 60a or 75c limits imposed by NEC romex ratings or the terminal ratings, and most run dedicated conduits, and voltage drop is actually not a code issue and is nearly never a factor in EV charging). Also, the #'s I quote above are whole breaker sizes. In most cases the wire above is good for like 65 amps but I only quote it as 60 amps since the Wall Connector does not have a 65 amp setting.

And when Glamisduner said you need to set the Wall Connector to 40 amps it is important to note he is referring to the 50/40 amp setting (so the circuit is a 50a circuit, but due to the 80%/125% rule for continuous loads you only get to use 40 amps). If you set the Wall Connector to 40/32 amps then you would be not getting the full possible speed out of the wire.

Also, Glamisduner is technically correct in that in some situations you could put in a 90a breaker with 4awg THHN copper in conduit, but you would be using the "next size up" rule which never comes into play on the Wall Connector due to it not having the ability to set its max to 85 amps for instance. You would have to set it to 80 amps and then there would be no reason to use a 90a breaker FWIW. You can never actually use the 90c rating of the #4 THHN (which is 95 amps) since the Wall Connector and any residential breaker you find will be limited to 75c terminal temperatures.

A few months back when I was at Lowes picking up the wire, they didnt have enough 4 awg for my run. They recommended 2 awg since it was there and they had enough. I said if you can price match, im game. Well now I have my HPWC on an 80 amp breaker and can load share if/when I end up with two Teslas. However, 2 awg wire is a massive pain. But I feel really good when I am charging at 48 amps that I am nowhere near the limit.

Was that 2 AWG THHN or Romex? (copper I assume?) If it was THHN in conduit then you could do a 100a breaker and 80a continuous to the car (or pair of cars if you load share) if you main electrical service can handle it. If Romex then you could do a 90a breaker.

Though what size ground wire did you run? You need 8 awg for any circuit over 60 amps.

 

[Sophias_dad]

Are you running neutrals? Why? The HPWC and mobile connectors do not use it. Save yourselves some pain and $ by only running two hots and a ground. I bought a Gen 1 mobile connector and Nema 6-50 so I only need to run 6/2 to charge at 40A which is enough even for a larger car than a Model 3 LR. I have also planned for a second 6/2 run if I get a second car.

The reason we started writing about 3 conductor systems is that the topic somewhat morphed into putting in a 14-50 outlet, which needs a neutral. I didn't run a neutral to my HPWC, and part of the reason I used 6/2 and not 4/2 romex is that 4/2 romex doesn't appear to be available.

 

[woodguyatl]

I just want to add some color to this apart for future folks googling: 4 AWG Copper Romex (NM cable) is good for a 70a circuit (and equivalent Wall Connector setting). 4 AWG Copper THHN (in conduit) is good for an 80 amp circuit (and equivalent Wall Connector setting). 6 AWG Copper THHN (in conduit) is good for a 60a circuit (and equivalent Wall Connector setting).

Note that the above does not correct for ambient temperatures, more than three current carrying conductors in one conduit, or voltage drop. Though in nearly all installations what I stated above holds true (because you derate for temp adjustments from the actual wire 90c temperature rating, not the artificial 60a or 75c limits imposed by NEC romex ratings or the terminal ratings, and most run dedicated conduits, and voltage drop is actually not a code issue and is nearly never a factor in EV charging). Also, the #'s I quote above are whole breaker sizes. In most cases the wire above is good for like 65 amps but I only quote it as 60 amps since the Wall Connector does not have a 65 amp setting.

And when Glamisduner said you need to set the Wall Connector to 40 amps it is important to note he is referring to the 50/40 amp setting (so the circuit is a 50a circuit, but due to the 80%/125% rule for continuous loads you only get to use 40 amps). If you set the Wall Connector to 40/32 amps then you would be not getting the full possible speed out of the wire.

Also, Glamisduner is technically correct in that in some situations you could put in a 90a breaker with 4awg THHN copper in conduit, but you would be using the "next size up" rule which never comes into play on the Wall Connector due to it not having the ability to set its max to 85 amps for instance. You would have to set it to 80 amps and then there would be no reason to use a 90a breaker FWIW. You can never actually use the 90c rating of the #4 THHN (which is 95 amps) since the Wall Connector and any residential breaker you find will be limited to 75c terminal temperatures.



Was that 2 AWG THHN or Romex? (copper I assume?) If it was THHN in conduit then you could do a 100a breaker and 80a continuous to the car (or pair of cars if you load share) if you main electrical service can handle it. If Romex then you could do a 90a breaker.

Though what size ground wire did you run? You need 8 awg for any circuit over 60 amps.

This may have been said already, but those people who are reluctant to run conduit because they have not done it before are likely to wish they chose to run conduit, (the plastic is easy to work with) one they start messing with large gauge romex.

 

[Glamisduner]

I just want to add some color to this apart for future folks googling: 4 AWG Copper Romex (NM cable) is good for a 70a circuit (and equivalent Wall Connector setting). 4 AWG Copper THHN (in conduit) is good for an 80 amp circuit (and equivalent Wall Connector setting). 6 AWG Copper THHN (in conduit) is good for a 60a circuit (and equivalent Wall Connector setting).

Note that the above does not correct for ambient temperatures, more than three current carrying conductors in one conduit, or voltage drop. Though in nearly all installations what I stated above holds true (because you derate for temp adjustments from the actual wire 90c temperature rating, not the artificial 60a or 75c limits imposed by NEC romex ratings or the terminal ratings, and most run dedicated conduits, and voltage drop is actually not a code issue and is nearly never a factor in EV charging). Also, the #'s I quote above are whole breaker sizes. In most cases the wire above is good for like 65 amps but I only quote it as 60 amps since the Wall Connector does not have a 65 amp setting.

And when Glamisduner said you need to set the Wall Connector to 40 amps it is important to note he is referring to the 50/40 amp setting (so the circuit is a 50a circuit, but due to the 80%/125% rule for continuous loads you only get to use 40 amps). If you set the Wall Connector to 40/32 amps then you would be not getting the full possible speed out of the wire.

Also, Glamisduner is technically correct in that in some situations you could put in a 90a breaker with 4awg THHN copper in conduit, but you would be using the "next size up" rule which never comes into play on the Wall Connector due to it not having the ability to set its max to 85 amps for instance. You would have to set it to 80 amps and then there would be no reason to use a 90a breaker FWIW. You can never actually use the 90c rating of the #4 THHN (which is 95 amps) since the Wall Connector and any residential breaker you find will be limited to 75c terminal temperatures.



Was that 2 AWG THHN or Romex? (copper I assume?) If it was THHN in conduit then you could do a 100a breaker and 80a continuous to the car (or pair of cars if you load share) if you main electrical service can handle it. If Romex then you could do a 90a breaker.

Though what size ground wire did you run? You need 8 awg for any circuit over 60 amps.

Hey thanks for clarifying that, I saw the NEC rating had a * at 95 amps for 4awg THHN without an explanation on the chart I was using, so 75c breaker rating is why the other chart I was using is suggesting using 80 amp breaker with 4awg then, and explains why you want 3awg or 2awg for maximum delivery to a HPWC!

 

[Glamisduner]

Are you guys having any trouble using the back wall entry with the larger gauge wires?

If your using conduit and are not coming in from the next room don't bother you can see my thread here for why:
Replacing 14-50 with HPWC, outlet on the wrong side of the stud

Although if your using Romex rear entry should work fine as you would just use a clamp.

 

[eprosenx]

Hey thanks for clarifying that, I saw the NEC rating had a * at 95 amps for 4awg THHN without an explanation on the chart I was using, so 75c breaker rating is why the other chart I was using is suggesting using 80 amp breaker with 4awg then, and explains why you want 3awg or 2awg for maximum delivery to a HPWC!

This is the chart I use as a quick reference, but the official table is in the 2017 NEC (NFPA 70). I think you would find it interesting to do their "free registration" so you can access it online. I forget the actual table # off the top of my head, but I reference it constantly.
Ampacity Charts - CerroWire

 

[Park2670]

Are you guys having any trouble using the back wall entry with the larger gauge wires?

Yes. Getting the two 2awg wires to make the "U" turn into the Wall Connector was extremely painful. Took me hours to get it right.

Yeah 3 seems to be the limit in 1" for 3awg.

I have two 2 awg and a 6awg ground. It was awful getting it into the 1" conduit.

Was that 2 AWG THHN or Romex? (copper I assume?) If it was THHN in conduit then you could do a 100a breaker and 80a continuous to the car (or pair of cars if you load share) if you main electrical service can handle it. If Romex then you could do a 90a breaker.

Though what size ground wire did you run? You need 8 awg for any circuit over 60 amps.

Copper THHN. I sized all the wiring and ground so I could eventually move to a 100 amp breaker, but I will need to upgrade my house sub panel and main panel first. So 80 amps it is for now.

 

[Feathermerchan]

Home charging needs boil down to haw many local miles driven and Wh/mile. Number of cars only matters as to how many charge outlets you need. I'm planning on two cars and about 10,000 miles per year total. at 300 Wh/mil that is about 3,000 kWh / year or 8.2 kWh per day. Assuming a 10 hour charge that requires 8.2 kW which on 240V is 34A total. I am running two 50A circuits to my garage. That should give me plenty of headroom. I'm running 6/2 so it is pretty easy to maneuver.

 

[Sophias_dad]

I'm planning on two cars and about 10,000 miles per year total. at 300 Wh/mil that is about 3,000 kWh / year or 8.2 kWh per day. Assuming a 10 hour charge that requires 8.2 kW which on 240V is 34A total. I am running two 50A circuits to my garage

I think your math is wrong there... 34amps times 240v times 10 hours is 82kwh per day, if I did my math right... It looks like you can get by on a 120v outlet....

4 miles times 10 hours times 365 is 14,600 miles per year....

 

[Park2670]

But there is going to be that one day you get home after a longer, cold drive and will need an extra 50 miles. Which is why I ended up installing the Wall Connector.

 

[Sophias_dad]

But there is going to be that one day you get home after a longer, cold drive and will need an extra 50 miles. Which is why I ended up installing the Wall Connector.

Yes, I would never advocate for having only a 120V charger.... it can barely be done in warm climates, and is just useless in the cold.

 

[Park2670]

Yes, I would never advocate for having only a 120V charger.... it can barely be done in warm climates, and is just useless in the cold.

When I have traveled in my car, I end up 450 miles away from home. I tried once with the 15 amp 120v plug. It had been charging for two days straight and not useful enough. I purchased the 20 amp 120v adapter, and it actually is enough to get the battery filled up over the weekend before driving home.

 

[Feathermerchan]

I think your math is wrong there... 34amps times 240v times 10 hours is 82kwh per day, if I did my math right... It looks like you can get by on a 120v outlet....

4 miles times 10 hours times 365 is 14,600 miles per year....

My math is corrected below.
I assumed 5,000 miles/year for two cars. That's 10,000 miles/year
I assumed 300 Wh/mile. The Model 3 is rated at 240 Wh/mile. I have the Performance and average nearer to 300.
10,000 miles X 300 Wh/mile is 3,000,000 Wh or 3,000 kWh.
3,000 kWh / 365 days is 8.2 kWh/day
I assumed a 10 hour charging window.
To get 8 kWh in 10 hours you have to charge at 0.8 kW.
0.8 kW is 800 W so 800 W / 240 V = 3.3 A
Two 50 A circuits is about 30 times as much as I'll need unless one car is a Rivian pickup.
Unless you drive an awful lot, I don't see the need for a 100 A sub panel in your garage.
One or two 50A circuits should be plenty.

I charge at 120V now and most of the time it is OK. The car is in the insulated garage. But sometimes I do need more.
There are a couple of superchargers around me and I have used them.
I do take my cord with me because my mother has a Nema 6-50. I need that because she lives in Kerrville and there are no superchargers near there.

 

[tls]

If your jurisdiction is on 2017 NEC, you should be able to use 6-6-6 copper or 4-4-6 AL type SE (including SER or SEU, I believe, but not type USE) cable.

Under 2017 code you are not required to derate this cable type to 60C so long as the conductors are 8 AWG or larger. This will get you significantly more ampacity than Romex (NM-B) without going to conduit. Certainly enough to charge at 48A.

The Lowe's site has 6-6-6 Cu for $2.24 a foot. But the 4-4-6 AL is a particularly good deal - $0.67/foot at wireandcableyourway.com.