House Electrical Upgraded, Finally! (and HPWC install)

mmh · Aug 2, 2014

The story:

I confirmed my Tesla order March 3rd, and shortly there after started seeking an electrician. I asked Tesla for a recommendation as I've never had to hire the services of a licensed electrician before. I consider myself fairly handy and can always fall back to my dad for anything tricky, but needing to do a service upgrade, and pull ~40' of 2AWG electrical cable wasn't something I felt comfortable with.

My house had 100AMP service, but with the Tesla I really wanted the full "Tesla Experience" with in-home 80AMP charging. My service had to be upgraded: I initially planned on going to 200AMP service, and was told by the local power company (Rocky Mountain Power) that I'd have to trench to the junction box, lay conduit and run new cable.

Tesla recommended the company "Gardener Energy". I had them come out to give me an estimate for the work. The guy started counting out loud: $1000 to run the cable, $3000 for a new breaker box, $1000 for a NEMA 14-50, $1200 in conduit, $4000 more if we need to run conduit to the junction box, "no we don't do the trenching, you'll have to find someone else to dig"... I asked them if they could guarantee a price UNDER $10,000... He could not. Gardener Energy even went on to say they may need to rewire my entire house (!) if they get into the breaker and find anything not up to code. Screw Gardener Energy.

I have a NEMA 10-30 plug in my garage. This allows me to charge at 240V 24A or 17mi/hr, which honestly was good enough for pretty much anything I do most of the time. But I was already dead-set on getting the 80AMP HPWC hooked up and being able to charge at 56mi/hr.

I called another electrician, Kyle Clark of ASK Electric (ASK Electric | Utah Electrician Serving Residences in Salt Lake City), and I HIGHLY recommend him for anyone who is in the Salt Lake Valley. Kyle recommended we do 150AMP service instead of 200AMP service, this would allow us to use the already buried service line, saving both a lot of effort and money. For $1,900.00, Kyle installed a new 150AMP electric service box, a 100AMP service box in the garage, ran 2AWG cable from the outside breaker box to the garage, installed a NEMA 14-50 (ground pin up), and hooked up the Tesla HPWC. He did everything to code and got permits from the city when needed.

My old service box (100A) before upgrade (actually before I even owned the house)

Upgraded service box (150A), `just` a little bit bigger.

Garage install and garage sub-panel

(The jars are for shooting/target practice.)

A plugged-in Tesla is a happy Tesla

ModelX · Aug 2, 2014

Very nice! Thanks for the recommendation!

GoBlue88 · Aug 2, 2014

Looks nice! Question: why did you install both the NEMA 14-50 and the HPWC?

mmh · Aug 2, 2014

GoBlue88 said:
Looks nice! Question: why did you install both the NEMA 14-50 and the HPWC?

Because it was $50 additional to have the electrician to do it now, and provides me with a semi-fast charge should the HPWC ever die in the future. Basically it's a backup option.

Bill D · Aug 3, 2014

With a 100A service box in your garage, it seems you can't simultaneously charge from both your 14-50 and your HPWC at their full rates (40A +80A), although you could limit the Tesla on the HWPC down to 40A whenever you are also using your 14-50.

I'm no expert, but I'm surprised your installation met code having both the 14-50 and HPWC on your garage 100A service, even if you only intend to use the 14-50 as a backup option "should the HPWC ever die in the future" as you said.

I also now have an HPWC on a 100A service in my garage and I'm looking how to add charging for a second EV at minimum expense, so let me know if I'm missing something here.

pgiralt · Aug 3, 2014

Bill D said:
With a 100A service box in your garage, it seems you can't simultaneously charge from both your 14-50 and your HPWC at their full rates (40A +80A), although you could limit the Tesla on the HWPC down to 40A whenever you are also using your 14-50.

I'm no expert, but I'm surprised your installation met code having both the 14-50 and HPWC on your garage 100A service, even if you only intend to use the 14-50 as a backup option "should the HPWC ever die in the future" as you said.

I also now have an HPWC on a 100A service in my garage and I'm looking how to add charging for a second EV at minimum expense, so let me know if I'm missing something here.

I did the same thing when I installed the HPWC. It passes inspection for the same reason you can add up all the breakers in your breaker panel and the total will be much higher than the main breaker for the house (if you even have a main). As long as the upstream breaker for that subpanel is rated correctly (100A) then if someone decides to draw 120A, it will just trip the breaker.

The he bigger question is actually whether the load calculation for the whole house checks out with only 150A service to the house. I would think even with just the HPWC alone that could push the house load calculation over the new 150A panel. I'm surprised they didn't do at least 200A service or even 400A as the cost shouldn't have been much more.

The NEC generally just deals with things that would make something a safety hazard and from a safety perspective there is nothing wrong with the sum of breakers in a panel being more than the breaker that feeds the panel. Just like you can plug two 1800 watt hair driers into the same bathroom circuit and trip the breaker.

Cottonwood · Aug 3, 2014

mmh said:
Because it was $50 additional to have the electrician to do it now, and provides me with a semi-fast charge should the HPWC ever die in the future. Basically it's a backup option.

I have the extra 14-50 next to my HPWC also. It's a good, cheap backup option. It also gives you a place to test your UMC before a trip to make sure it's still working.

mmh · Aug 3, 2014

pgiralt said:
The he bigger question is actually whether the load calculation for the whole house checks out with only 150A service to the house. I would think even with just the HPWC alone that could push the house load calculation over the new 150A panel. I'm surprised they didn't do at least 200A service or even 400A as the cost shouldn't have been much more.

It does, the only other heavy load in my system is the an electric stove which draws 40A max, and I don't have air conditioning. One of the benefits of living in a dry climate, evaporative coolers use little power and work very well as long as they're maintained.

The cost to do 200A service would have been much higher, as I would have needed to run new conduit and a new service line from the house to the power companies' junction box. Which very inconveniently is on the complete opposite side of the house. This also would have damaged 3 sprinkler systems, and possibly the cable companies' line.

At minimum the cost would have doubled if I had done all the trenching myself and laid the conduit. If I paid someone for this work I was looking at closer to $6000.

Going with 150A service instead allowed me to use the existing service line and, like I said in my original post, saved a lot of effort and money.

ecarfan · Aug 3, 2014

GoBlue88 said:
Looks nice! Question: why did you install both the NEMA 14-50 and the HPWC?

I did something very similar in my house: from my 200A main panel connected a new 100A sub panel and from there connected an 80A HPWC and a 40A NEMA 14-50. Charge my Model S on the HPWC and have the 14-50 available for my next EV.

Of course I will not be able to use the HPWC and the 14-50 simultaneously at full amperage but that is easy to avoid through time scheduling.

Bill D · Aug 3, 2014

ecarfan said:
Of course I will not be able to use the HPWC and the 14-50 simultaneously at full amperage but that is easy to avoid through time scheduling.

This concept makes sense. I'm now wondering if I could put two HWPCs on my one 100A breaker and simply avoid overloads through time scheduling and/or limiting the max current on each Tesla. Since almost all my charges are overnight, it's extremely rare that I need to charge above 40A, but in the rare occasion when I do need 80A for either car, it will be available. This makes perfect sense, but will it meet code?

NigelM · Aug 3, 2014

mmh said:
It does, the only other heavy load in my system is the an electric stove which draws 40A max, and I don't have air conditioning.

A good electrician would have done a quick load calculation with you. You may not have air conditioning but apart from your stove I'll bet you have a refrigerator? Garbage disposal? Microwave? Dishwasher? Washer? Dryer? Lights? Fans? PC? TV? These things all add up pretty quickly if you're using more than half your service capacity on the HPWC.

There's lots of simple spreadsheets around to total up your load; here's a random one.

mmh · Aug 3, 2014

NigelM said:
There's lots of simple spreadsheets around to total up your load; here's a random one.

So even then I'm fine. That's assuming of course that I'm running, the electric stove, oven, every light bulb and appliance in my house, charging my car @ 80A, running 2 electric clothes dryers, and the fridge.

But still, even if the loads didn't add up, I wasn't willing to pay the extra $$ to get 200A or more service. I would have lived with the unfortunate truth that I couldn't run the oven, the stove and both clothes dryers while charging my car without flipping a breaker.

NigelM · Aug 3, 2014

It's a good exercise to do for piece of mind. We have a 400A service but we do have AC systems etc and a Roadster so I always charge the Model S on the timer at 3.00am just to be certain I'm not tripping anything else.

dsm363 · Aug 3, 2014

mmh said:
View attachment 55417

So even then I'm fine. That's assuming of course that I'm running, the electric stove, oven, every light bulb and appliance in my house, charging my car @ 80A, running 2 electric clothes dryers, and the fridge.

But still, even if the loads didn't add up, I wasn't willing to pay the extra $$ to get 200A or more service. I would have lived with the unfortunate truth that I couldn't run the oven, the stove and both clothes dryers while charging my car without flipping a breaker.

Sounds like you did the best thing possible. As Nigel said you can simply time your charge at 3AM or so at 40A and you'd likely never run into problems.

Park2670 · Aug 3, 2014

Looks like a nice compromise to overdoing the entire house. My brand new home was only run with 100amp service (small townhome) and I wont ever have the ability to use a HPWC. But I did have a 14-50 installed, so at least I can charge the car.

Next up is getting some solar mounted to offset the car.

PhilBa · Aug 3, 2014

mmh said:
Because it was $50 additional to have the electrician to do it now, and provides me with a semi-fast charge should the HPWC ever die in the future. Basically it's a backup option.

I did the same thing. It took several tries with my electrician to get the point across. He was willfully difficult about it.

internauts · Sep 7, 2014

This is exactly what I was planning. Glad to see it is doable! Also, it is easy to add while electrician is there, and that will work for the next EV car too.

FlasherZ · Sep 7, 2014

Bill D said:
This concept makes sense. I'm now wondering if I could put two HWPCs on my one 100A breaker and simply avoid overloads through time scheduling and/or limiting the max current on each Tesla. Since almost all my charges are overnight, it's extremely rare that I need to charge above 40A, but in the rare occasion when I do need 80A for either car, it will be available. This makes perfect sense, but will it meet code?

Yes. 210.19(A)(I) states that branch circuits are to be sized per the maximum load to be served. If you intend to assure that only one charges at any given time, you'll be fine (you do not have to prevent oversubscription of the circuit). Of course, the wiring methods to be used must pass code, so you can't stick two sets of wires into the breaker or oversubscribe the lugs in one HPWC to daisy-chain them. You'll need to use something like three Polaris IPLD 3/0-3's (usually $50ish each) to join them in a junction box, and you can substitute a large (rated for 4 x 8ga) wire nut for ground if you desire. Be sure the box is big enough to contain the wires being joined and the connectors.

This is possible because both HPWC's would be rated for the branch circuit size. You are not permitted to install an HPWC configured for more than a 50A circuit with a NEMA 14-50 receptacle on the same circuit, because a 50A receptacle may not be placed on a branch circuit larger than 50A. Likewise, you're not permitted to install a larger circuit than what the HPWC's are configured for (for example, you would not be able to put in a 150A circuit breaker and connect 2 HPWC's configured for 70A each) - you may only have identically configured HPWC's on the same branch circuit, sized for one.

...and in most cases, the electricians will balk at this and recommend you just install a second circuit unless something absolutely prevents you from doing so, just because it's the safer and better thing to do. Most electricians would likely recommend a feeder to a subpanel in the garage and then branch off with 2 circuits, each to an HPWC - even if the feeder is the same size as one HPWC.

Bill D · Sep 7, 2014

FlasherZ - Thanks for the good news that this dual HPWC idea meets code and thanks for the well-detailed advice (as usual).
I was hoping it would meet code because the 200A panel in my garage is full and adding a subpanel would be very awkward.
Do you see any problem (code or otherwise) with me adding that junction box near the ceiling where you see the 1" conduit coupling located in this photo?
My new 1" conduit would run across the wall from the added junction box and curve down to the new HPWC that I install between the other two garage doors.
Do you have any suggestion where I might find a suitable junction box? (I'm using two 3ga and one 8ga)

FlasherZ · Sep 7, 2014

When you're working with Polaris connectors (which tend to be pretty large), you need a bigger box; standard 4" J-boxes don't really work for that wiring and those connectors. Junction boxes must be accessible (meaning you can't bury/cover them with any building materials). There are lots of options based on your space, home depot or an electrical supply company can get you what you need.

I don't make a suggestion because it depends upon how much of a pain in the rear you want it to be, and whether you mind a larger box. I prefer the larger boxes to work in, especially if steel, with those sharp edges and having to work the wires into it.

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