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HPWC Amp and Wire Specifications

chriSharek

Member
Feb 19, 2015
873
70
Sarasota, FL
I'm preparing for my baby 9 months out (fitting, right?). I hope to take delivery prior to our annual Thanksgiving trip to Grandma & Grandpa's. I'm getting a single charger S85. Is the spec for the HPWC a 2-pole 40 amp breaker or 50? Also, based on the breaker size, what size wires will I need? #6? Thanks for the help.


And just FYI, I did try to search and find answers on this on Tesla's site as well as this forum with little success.
 

dirkhh

Middle-aged Member
Jul 7, 2013
3,638
128
Portland, OR, USA
By default the HPWC requires a 2 pole 100A breaker and #3 wire

Or to quote FlasherZ's home charging FAQ

WHAT WIRE SIZES SHOULD BE USED FOR INSTALLING MY HPWC?

Note: All wire sizes assume copper conductors!

For wire-in-conduit, 3 AWG THHN (dry locations) or THWN (wet locations) is sufficient to carry 100 amps, but many electricians will use 2 AWG to ensure there is enough headroom, and it’s carried more widely by supply houses. The ground wire must be a minimum of size 6 AWG.

I am told that Canadian consumers have the option of type NM cable (3/3+ground) for this installation, but NEC does not permit this (because 3 AWG must be used at the 60 degC rating, only 85 amps).

If these conductors will ride in the same conduit as another circuit, they must be “de-rated” and 2 AWG is required.

If the HPWC is set to 40A charging with the little dip switches then technically 8AWG on a 50A breaker should be enough.
The breaker always needs to be 25% higher than the continuous charging current.
 

SabrToothSqrl

Active Member
Dec 5, 2014
3,816
3,228
PA
you can adjust the dip switches for your install, but with only one onboard charger, there is no advantage to the HPWC... wire in a NEMA 14-50 with 6 gauge wire and a 50 amp breaker.

the HPWC, to run the full 80 amps needs 3 gauge wire and a 100 amp breaker.

I'm still on the fence about the HPWC, that way I can leave my UMC in the car for simplicity. (I've never driven w/the UMC in the trunk).
 

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,088
173
Colorado
The breaker always needs to be 25% higher than the continuous charging current.

This is true in the vast majority of installations, but is not true "always"; the code does allow for breakers that are rated for 100% continuous load. For example, the breakers used in Tesla's Superchargers are rated at 100% continuous load and are sized that way.

That being said, I don't know of any breakers available for home sized panels that are 100% continuous rated. For all installs that we are likely to see in our houses, the breaker must be sized at 125% of the continuous load, or stated another way, the continuous load must be no more than 80% of the breaker size.
 

jthompson

JThompson
Supporting Member
I'm preparing for my baby 9 months out (fitting, right?). I hope to take delivery prior to our annual Thanksgiving trip to Grandma & Grandpa's. I'm getting a single charger S85. Is the spec for the HPWC a 2-pole 40 amp breaker or 50? Also, based on the breaker size, what size wires will I need? #6? Thanks for the help.

Tesla has an HPWC install handbook they can give you (or I can send you). But I am curious - if you have a single charger, you will not be able to use the 80 amp charging capability the HPWC can provide (you are limited to 40 amps with a single charger). Why not go with a less expensive NEMA 14-50 outlet and buy an extra UMC? Or are you planning on buying the second on-board charger after delivery?
 

SW2Fiddler

We Are Cognitive Dissidents
Mar 19, 2014
2,362
3,270
Houston TX
ANY way we could convince you on a second charger?
I might be waiting to charge after you some day at a public charger greater than 40A.
 
Last edited:

chriSharek

Member
Feb 19, 2015
873
70
Sarasota, FL
@FlasherZ: Thanks! I am horrible at searching these sites. Most appreciated.

@JThompson: The additional UMC is $650, right? At $750, I can get the permanently installed HPWC wired in with a holster and all. Plus, I understood that the NEMA plugs are not meant for outside (I have a carport; the wife gets the garage for her open top jeep)

Will the UMC automatically pop the charge door open like the HPWC will?

- - - Updated - - -

SW2Fiddler, what public charging station do you know of that's > 40A? You know the Superchargers bypass the onboard chargers anyway. I'd rather have the SAS than the dual chargers! :)
 
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jthompson

JThompson
Supporting Member
@chriSharek: Sorry about that! I have not kept up with Tesla accessory pricing and did not notice the HPWC prices fell so far from what it was originally. And you are correct about the exterior install - the HPWC is fine for that. Although numerous members (severla of them good friends of mine) have also setup to use a spare UMC outside, and it works fine as well. And yes, the button on the UMC and HPWC do both pop open the charger port.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,028
1,025
Will the UMC automatically pop the charge door open like the HPWC will?

Yes, the silver button on top does the same.

Even if I could only configure it for 40A charging load (50A circuit size), I would still consider a wall connector. They're now much more reasonable ($750) and they allow you to keep your mobile cord in the car without having to wrap it up for trips; they are built for heavier duty, and the cord is 7' longer. You can put it on a variety of circuit sizes, depending upon various factors (whether your service can support it, etc.).

- - - Updated - - -

That being said, I don't know of any breakers available for home sized panels that are 100% continuous rated. For all installs that we are likely to see in our houses, the breaker must be sized at 125% of the continuous load, or stated another way, the continuous load must be no more than 80% of the breaker size.

I know where you can get them, but as you say they're special-purpose and on a per-amp basis they're far, far more than the overall cost of sizing to 125%. So I don't even talk about them, so as not to confuse anyone here. :)

- - - Updated - - -

Why not go with a less expensive NEMA 14-50 outlet and buy an extra UMC? Or are you planning on buying the second on-board charger after delivery?

The difference between UMC and HPWC now is $100. I think the marginal benefits of HPWC over second UMC are far greater than the $100 cost. That was not true when the HPWC was $1200, though.
 

chriSharek

Member
Feb 19, 2015
873
70
Sarasota, FL
@FlasherZ, you are bang on. That is exactly why I was going to get the HPWC: holster, outside install, permanent, and allows me to keep my mobile connectors in the car, MOBILE! I currently have a "HPWC" for my Volt that I'm planning to move for my son. It's worked great for 4 years and that allows me to keep the 120V charger in the trunk for mobile opportunities.

@Lloyd - thanks. This install guide is more comprehensive and detailed than the older one. The one page showing the dip switches (had to stop giggling like a girl) clearly shows that a 40 amp or 50 amp breaker could be used. And for a single charger on the car, I'll opt for the 50 amp to get my maximum 29 miles/hour of charge. But, looking at your ampacity chart, if I'm pulling 40 amps, I only need to use a #8 wire? That doesn't sound sufficient for some reason.
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,335
2,203
San Luis Obispo, CA
@FlasherZ, you are bang on. That is exactly why I was going to get the HPWC: holster, outside install, permanent, and allows me to keep my mobile connectors in the car, MOBILE! I currently have a "HPWC" for my Volt that I'm planning to move for my son. It's worked great for 4 years and that allows me to keep the 120V charger in the trunk for mobile opportunities.

@Lloyd - thanks. This install guide is more comprehensive and detailed than the older one. The one page showing the dip switches (had to stop giggling like a girl) clearly shows that a 40 amp or 50 amp breaker could be used. And for a single charger on the car, I'll opt for the 50 amp to get my maximum 29 miles/hour of charge. But, looking at your ampacity chart, if I'm pulling 40 amps, I only need to use a #8 wire? That doesn't sound sufficient for some reason.

Remember to add 20% for continuous use. For a 50 amp breaker I would use #6.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,028
1,025
@Lloyd - thanks. This install guide is more comprehensive and detailed than the older one. The one page showing the dip switches (had to stop giggling like a girl) clearly shows that a 40 amp or 50 amp breaker could be used. And for a single charger on the car, I'll opt for the 50 amp to get my maximum 29 miles/hour of charge. But, looking at your ampacity chart, if I'm pulling 40 amps, I only need to use a #8 wire? That doesn't sound sufficient for some reason.

See my FAQ in my signature.

If you're using wire-in-conduit, #8 is sufficient for 40A charging load (50A circuit rating), assuming typical THHN.
If you're using NM-B (Romex), you must use #6. Article 334 specifies that Romex cable ampacity must always be considered from the 60 degC column, except inspecific derating situations, but must never be more than the 60 degC column.

- - - Updated - - -

Remember to add 20% for continuous use. For a 50 amp breaker I would use #6.

You add 25%, not 20%. Charging current * 1.25 = wire/breaker size requirement. So 40A charging load requires conductors & breaker at 50A.
 

SW2Fiddler

We Are Cognitive Dissidents
Mar 19, 2014
2,362
3,270
Houston TX
SW2Fiddler, what public charging station do you know of that's > 40A? You know the Superchargers bypass the onboard chargers anyway. I'd rather have the SAS than the dual chargers! :)
Charging Time. Arguably, the single possible compromise/limitation/downside of an amazing car ownership experience. Why anyone would not want to minimize this as much as possible, why even Tesla Product Specialists have been heard to advise against a second charger, maximizing - future-proofing - the car's charging capability, I just cannot fathom. At least the dual-charger option is no longer a Get-It-At-Factory-Or-Regret-It decision; you have lots of time before and after baby's delivery :)

I'll answer your question with where my Duals should help out (me, and Anyone Waiting For Me To Finish) on a hypothetical trip towards your area. Does not even list non-Tesla >30A spots like Sun Country Highway, which are still increasing. Many Tesla owners find they do want to travel MUCH more than they did in their previous cars.
I would be shocked if this list ain't about doubled by your Model S's first birthday, too:
FLORIDA

Boca Beach Club, Boca Raton
Charger

Boca Raton-Town Center at Boca Raton
Store

Waldorf Astoria Boca Raton Resort & Club
Charger

Bonita Beach Vacation Rental Home, Bonita Springs
Charger

South Seas Island Resort, Captiva
Charger

Dimmitt Automotive Group Collision Center, Clearwater
Charger

Dania Beach
Store, Service Center

Bahama Bay Resort, Davenport
Charger

Banyan Air Service, Fort Lauderdale
Charger

Hilton Fort Lauderdale Beach Resort
Charger

Victoria Park Hotel, Ft. Lauderdale
Charger

Cheeca Lodge & Spa, Islamorada
Charger

Jacksonville
Service Center
COMING SOON

Four Points by Sheraton Jacksonville Beachfront
Charger

Ocean Key Resort and Spa, Key West
Charger

Orlando-Longwood
Store, Service Center

Port d'Hiver Bed & Breakfast - Select Registry, Melbourne Beach
Charger

InterContinental Miami
Charger

Mandarin Oriental, Miami
Charger

Miami-Dadeland
Store

Eden Roc Miami Beach
Charger

Miami-Lincoln Road, Miami Beach
Store

The Ritz-Carlton, South Beach, Miami Beach
Charger

GEM Remotes, Naples
Charger

Ritz Carlton - Golf Resort, Naples
Charger

The Ritz-Carlton, Naples Beach Resort
Charger

The Breakers, Palm Beach
Charger

West Palm Beach Riviera Beach
Store, Service Center

Sarasota-University Town Center
Store

Four Points by Sheraton Tallahassee Downtown
Charger

Eddie V's Prime Seafood, Tampa
Charger

Epicurean Hotel, Tampa
Charger

Tampa
Store, Service Center

One quote and I am off the soapbox...
Frequently stated at the Houston Galleria HPWC and HPC: "But I only got Single Charger, or I'd be done sooner. Sorry!"
 
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chriSharek

Member
Feb 19, 2015
873
70
Sarasota, FL
Remember to add 20% for continuous use. For a 50 amp breaker I would use #6.

Just a follow up on the install. I went to Home Depot to get the #6 wire and the #4 was a penny more per foot! Since I was going 90 feet, I thought it would be better to get the #4. It was a challenge cramming two of them through my 1" conduit with the #8 ground, but I managed!
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,028
1,025
Just a follow up on the install. I went to Home Depot to get the #6 wire and the #4 was a penny more per foot! Since I was going 90 feet, I thought it would be better to get the #4. It was a challenge cramming two of them through my 1" conduit with the #8 ground, but I managed!

Great to hear... 2 #4's and a #8 should have gone fairly easily through a 1" conduit, even at 90 ft - what was the biggest challenge?
 

mitch672

Active Member
Jul 1, 2012
1,861
15
Stoughton, MA
now that you have 95A rated THHN, you might consider buying a 70A breaker, if your panel can support the load, in case you have a visitor with a dual charger...
 

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,088
173
Colorado
now that you have 95A rated THHN, you might consider buying a 70A breaker, if your panel can support the load, in case you have a visitor with a dual charger...

The new HPWC's can be set to 100, 80, 50, 40, 30, 20, or 15 Amp breakers for 80, 64, 40, 32, 24, 16, or 12 Amp charging. See page 16 of http://www.teslamotors.com/sites/default/files/pdfs/tesla-wall-connector-installation-80A-12A.pdf

With #4 wire, you may want to consider putting in an 80 Amp breaker and setting the HPWC to 80/64 for 64 Amp charging.
 

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