What's up with HPWC?

[aesculus]

I had to go out and pull the subpanel to check.

• Ground was part of the bundle. It looks like 1/0 too, un-covered.
• Shop Eaton 16-Circuit 8-Space 125-Amp Main Lug Load Center at Lowes.com
  
• Would do it the same today

 

[TechVP]

• Ground was part of the bundle. It looks like 1/0 too, un-covered.

• Shop Eaton 16-Circuit 8-Space 125-Amp Main Lug Load Center at Lowes.com

• Would do it the same today

@aesculus That was very cool of you to remove the cover. I then assume you used a Romex or similar cabling.
I calculated for my ground line install I need an 8 AWG minimum. I have 6 AWG readily available, which should be ample for a 33' run.

Here's my next question: My power company, after consultation, suggested that my feed at 200A should be sufficient.
Looking into this further I was curious about your experience.
What is the rating of your main panel? Is it 200 Amp -- or greater than that?
And with air conditioners + regular daily household use did you experience any issues with HPWC charging?

 

[aesculus]

My power co., PG&E, did load calcs for me for a 2 year period. They said my 200 amps was fine provided I did not try to run my heat pumps, dry clothes, run the spa, cook a turkey and charge my car at 72 amps simultaneously. Off hours they said I never got close so if I used my charger during the 11pm to 7am period, I would be fine. They incented me by providing a rate that was really cheap then and really expensive outside of that period.

So far no issues. They did say that if I ever experienced brown outs then it would be time to have them run some additional load calcs. If it turned out to be an issue then I could install another meter and panel and run the car solely from that. I put an extra 8 feet of cable in the wall just for that purpose. If I need to I can just put another load center next to my existing 200 amp panel and drag the 1/0 over to it's own panel/meter. Maybe someday when we have nothing but EV's, but not right now.

 

[TechVP]

My power co., PG&E, did load calcs for me for a 2 year period. They said my 200 amps was fine provided I did not try to run my heat pumps, dry clothes, run the spa, cook a turkey and charge my car at 72 amps simultaneously.

@aesculus

Thanks for confirming my inquiry on the 200 amp panel. My utility provided a very similar set of instructions.
If I can avoid changing out meter + panel, all the better. Same general warning about brown outs. Timed charging is a definite benefit.
Thanks for the extra loop / length suggestion of 1/0 in the panel -- good advice.
Very informative.

 

[aesculus]

Thanks for the extra loop / length suggestion of 1/0 in the panel -- good advice.

Just to be clear you need that in the wall and not the panel. Not enough room in there.

 

[TechVP]

Just to be clear you need that in the wall and not the panel. Not enough room in there.

Thanks again. In this case I built in conduit before sheetrock was installed 10 years ago that spans the overhead length of the garage. At the time it was futurproofing for an RV, or whatever else came along. Branching & exposing that conduit is no problem. It will be an install of TTHN 1/0 for the full run. I'll see what I can fit in the panel. If necessary I can extend conduit by a few feet.

 

[aesculus]

If necessary I can extend conduit by a few feet.

If you have enough room you can always splice in the panel I guess. Some inspectors might wince but ...

 

[TechVP]

Yeah with 100A theoretical load, splicing isn't a preferred option.

On another note I stopped into the local showroom and asked the managers there of the people who install the HPWC, how many do self installs. They said they had not heard of one. Your guides here are much appreciated. I thought I should get educated before I ping local contractors.

@aesculus What height from the floor is
a) the bottom corner of your sub panel and
b) the bottom of your HPWC?

I have been hearing 48". But could use some clarification as to where you start measuring from. Anybody who can site NEC code is welcome.

 

[BrokerDon]

We had one of Tesla's recommended electricians install our 1st Generation HPWC using the electrician supplied Load Calc submitted with our building permits. Our single phase 200A / 240V Main Service Panel and its completely stuffed with breakers for our 2006 constructed 3,300 sq. ft. house. The Tesla HPWC 100A breaker is in the 100A subpanel that's also stuffed. Our HPWC has worked flawlessly (since our moderate Mediterranean climate rarely requires our 2 central AC units to run at night when our Tesla is charging on SCE's TOU-B-D-SDP "Super Off-Peak" rate (10;00 PM TO 8:00 AM). We typically charge our Tesla P85D with dual chargers at 60A to keep the HPWC cable & plug from getting hot which would most likely shorten its life.

 

[aesculus]

a) the bottom corner of your sub panel and
b) the bottom of your HPWC?

55" and 40" respectively.

 

[TechVP]

@FlasherZ when adding a subpanel for a 100A circuit, looking at the main panel --
While installing for a 100A subpanel the only space I have open is towards the very bottom of the main panel.
Does code designate that the subpanel circuit breakers be toward the top and closest to the main breaker/lugs?
Perhaps it's only convention that is where other major appliances are placed.

 

[ccutrer]

@FlasherZ when adding a subpanel for a 100A circuit, looking at the main panel --
While installing for a 100A subpanel the only space I have open is towards the very bottom of the main panel.
Does code designate that the subpanel circuit breakers be toward the top and closest to the main breaker/lugs?
Perhaps it's only convention that is where other major appliances are placed.

I'm not a code expert, but I believe breaker placement is mostly a "style" thing per electrician and/or region. The only rule I'm aware is that when you have a back fed breaker for solar, and the sum of the breaker protecting the sub panel and the backfed breaker exceed the bus bar rating, you have to place the backfed breaker at the opposite end of the bus bar from where power is supplied, in order to prevent hotspots that could exceed the bus bar's rating (there's also a limit to how much you can exceed the rating of the bus bar in such a scenario).

 

[TechVP]

only rule I'm aware is that when you have a back fed breaker for solar

Thanks for the hints. Maybe by 5 years I'll save up for the solar portion. May have outgrown the current main panel by then. Wife's taking interest in my X100D. Is that a good thing???

 

[TechVP]

@FlasherZ looking for some clarification.
Does this LB fitting reset the 360 code conduit bend limitation?

 

[FarmerDave]

I know the new HPWC can daisy-chain to another HPWC to charge two cars sequentially. Will that work if the second HPWC is the older model?

I'm trying to plan ahead for when a Model 3 joins my Model X in the garage.

 

[ccutrer]

I know the new HPWC can daisy-chain to another HPWC to charge two cars sequentially. Will that work if the second HPWC is the older model?

I'm trying to plan ahead for when a Model 3 joins my Model X in the garage.

No. Both wall connectors must be the new model, and you run an additional low voltage wire between them for communication purposes. The old model does not have the terminals (or the internal smarts) for communication with other wall connectors.

 

[FarmerDave]

No. Both wall connectors must be the new model, and you run an additional low voltage wire between them for communication purposes. The old model does not have the terminals (or the internal smarts) for communication with other wall connectors.

Thanks. That means either two circuits or two of the newer HPWC's.

 

[tga]

I know the new HPWC can daisy-chain to another HPWC to charge two cars sequentially. Will that work if the second HPWC is the older model?

I'm trying to plan ahead for when a Model 3 joins my Model X in the garage.

The only daisy chaining is on the data comm path. There are no "AC output" terminals to feed the second HPWC. You need to split the circuit before the HPWC's, either using something like Polaris connectors or a sub panel.

 

[FarmerDave]

The only daisy chaining is on the data comm path. There are no "AC output" terminals to feed the second HPWC. You need to split the circuit before the HPWC's, either using something like Polaris connectors or a sub panel.

Thanks, that's helpful.

 

[Alset72]

Apologies if this has been explained before, but I could not find the answer reading through this thread. Here is my situation and resulting questions (please note that I am neither an electrician nor do I know much about electric circuits. I will hire an electrician for the install, right now I am just trying to figure out whether I need to buy one or two HPWCs):

Situation:
- I currently have a NEMA 14-50 for my Model S with a regular single charger charging at 40 Amps
- I have a Model X on order with the upgraded 72 Amp charger
- I am planning on getting the HPWC to use the full 72 Amp on the Model X
- The total amperage going to my garage is 100 Amp and don't think I can get it any higher
- Other than a few lights in the garage I don't have anything else going on there

Questions:
- Should I replace the existing NEMA 14-50 with a second HPWC and daisy chain the two HPWCs?
- Or can I have one HPWC on the Model X and the NEMA 14-50 on the Model S?