FAQ: Home Tesla charging infrastructure Q&A

[Ostrichsak]

Depends on the local codes.

Assuming no code issues, you don't need a subpanel, just two individual runs and two circuit breakers. Generally you need a subpanel when:

1. Local code says so.
2. You have multiple outlets far from the main panel (far means the cost of running separate wires is more than the cost of the subpanel and wiring to it.)
3. There is no space for additional breakers in the main panel. (Although in this case it might be better to increase the size of the main panel.)

I'll add that while you can't Daisy chain a HPWC to a NEMA 14-50 outlet your electrician can pull both wires at the same time. If you're not locating them far from the panel it won't save much but for those with longer runs it should save some labor.

 

[boaterva]

In the thread that has the sample installations, my install is exactly this. See my sig for photos. We put in a simple subpanel that had a 100 A breaker for the HPWCs (two 80 A ones in parallel, there is no power ‘daisy chain’, it’s the data connection that is daisy chained...!) and a 50 A breaker for the 14-50 and a simple device to be sure only one of them was active at one time (required).

 

[davewill]

I am getting an hpwc installed. What is the cheapest way to get a 14-50 installed as well? Does the daisy chaining of hpwcs only work with other hpwcs or is there a way to add a 14-50 outlet to the mix? I intend to have both installed within a couple feet of the main box... would I still need aa subpanel? Or is that only for distant installations?

As said above the power isn't daisy chained. So you need a junction box of some sort to connect power to both of the wall connectors. By the time you buy a large junction box and the Polaris connectors to do the splices, it can be just as cheap to simply use a small subpanel or load center. It also gives you an easy way to cut power to each wall connector individually. As far as using the 14-50 for the second wall connector and load sharing, there are ways to do that, but there is no way to have different amperage limits for the two wall connectors that are sharing, so if WC1 is on a 60a circuit and WC2 is on a 50a circuit, you'd have to have both of them share 50a.

If we knew what size circuit you wanted to run for the first wall connector, we could do a better job advising you. Assuming you want 60a for the two wall connectors, I'd do the subpanel and use wire sized for 60a. For now use a 60a breaker for the wall connector and a 50a breaker for the 14-50. When and if wall connector number 2 comes, replace the breaker with 60a, remove the 14-50, hard wire the new wall connector and run the data cable to have them share the load.

My logic is that if you have two wall connectors, you won't need to have the 14-50 as a backup. The general idea can work for an bigger circuit, except that the wire may be too big for the 14-50 outlet. In that case, you might have to rerun the wire from the subpanel to the new wall connector to go bigger than 50a (or you could keep the 14-50 and add the new WC on a third circuit from the subpanel).

All that said, it's easy to overthink and overbuild on this stuff, and there would be nothing wrong with just running the one circuit for the wall connector you need now, and worry about expansion if and when you actually get another EV. Who knows if you'll even live in the same house by then?

 

[boaterva]

The reason we installed the 14-50 was to have a backup in case a power surge or something fried the HPWCs. With two Teslas we would definitely need a better way to charge than running an extension cord and adapter to a dryer outlet (in that case)!

 

[im.thatoneguy]

It's to add a Destination Charger for a BnB. Tesla has cut way back on its free DC program but we're hoping to get on the map after the installation out of pocket as a form of marketing for Tesla owners looking at the map and deciding where to go based on listed chargers. At the very least we can offer it as an amenity to guests even if it never gets officially listed in the UI. We also want the 14-50 as an option in case guests drive a bolt or some other non-Tesla. Only one or the other would ever be in use (aka fit in the garage).

Gen3 of the HPWC should offer a 14-50 built in. Would probably be a good solve for many Tesla customers. Feed the 14-50 at 50 amps and use whatever is left over in the HPWC just like shared Superchargers.

Sounds like in my case two runs from two breakers would be the cheapest\best option if code allows. Will require a couple extra 15A 120v breakers to be tandem'ed to make room though. I'm thinking 60A to the HPWC since that's max Model 3 charge speed anyway and then obviously 50A to the 14-50.

 

[davewill]

It's to add a Destination Charger for a BnB. ... We also want the 14-50 as an option in case guests drive a bolt or some other non-Tesla. Only one or the other would ever be in use (aka fit in the garage)..

Might I suggest that you install a J1772 EVSE rather than a 14-50 for the second connection. Most non-Tesla EV owners out there that wouldn't be able to make use of the 14-50. You could also install a Jesla from QuickChargePower.com, and then go ahead and do load sharing with the first wall connector.

 

[im.thatoneguy]

Ouch that's $900. Seems like the better example is the Jdapter for $250. That would be then only one breaker, one charging station and then non-Teslas can just use the adapter.

 

[davewill]

Ouch that's $900. Seems like the better example is the Jdapter for $250. That would be then only one breaker, one charging station and then non-Teslas can just use the adapter.

That would work fine, too, since two cars can't park at the same time to charge there anyway. The only downside is having to get the adapter (and knowing that one is available) before the guest can charge. A small sign would take care of that, I suppose. Sounds much cheaper than running a second circuit.

 

[tga]

Clipper Creek HCS-50 (40A on a 50A circuit) is only $635 - 40A Level 2 EVSE HCS-50 | ClipperCreek

HCS-40 (32A on a 40A circuit) is a little cheaper - 32A Level 2 EVSE HCS-40 | ClipperCreek

 

[snort]

I think thatoneguy was also asking whether the 14-50 can be daisy-chained into the HPWC V2 load-sharing scheme. The answer is no.

The 14-50 is a dumb outlet. The HPWC V2 has a load sharing scheme that will give all the power to one HPWC if none of the others are asking, but will split the power if some are. It requires the "plug" to understand what the demand is and modulate it in response to directives from the master unit. To do this requires active circuitry to respond to those directives, which the 14-50 does not have.

The HPWC seems to be the cheapest EVSE on the market that does have this capablilty, b.t.w. I would be very happy to learn of a cheaper one.

-Snortybartfast

 

[diamond.g]

I think thatoneguy was also asking whether the 14-50 can be daisy-chained into the HPWC V2 load-sharing scheme. The answer is no.

The 14-50 is a dumb outlet. The HPWC V2 has a load sharing scheme that will give all the power to one HPWC if none of the others are asking, but will split the power if some are. It requires the "plug" to understand what the demand is and modulate it in response to directives from the master unit. To do this requires active circuitry to respond to those directives, which the 14-50 does not have.

The HPWC seems to be the cheapest EVSE on the market that does have this capablilty, b.t.w. I would be very happy to learn of a cheaper one.

-Snortybartfast

I don't think it is the plug, per se. There is a comms port that have to be hooked up to all the WC's that enables them to "talk" to one another to determine who needs the higher load. Unless Tesla has removed said port from the 14-50 version, or otherwise disabled it, it too should be able to participate in load sharing. This doesn't answer if NEC allows such a thing though.

 

[im.thatoneguy]

Theoretically, how it could work is that the master HPWC measures amperage flowing through itself and regulates the left-overs to the charging cable.

So 100A Breaker -> 80A max HPWC -> 50A Outlet.

If the outlet was drawing 40A the HPWC would limit itself to 40A. If the outlet was drawing 0A it would go full 80A. And if the Outlet tried to draw > 50A it would reset just like if a Tesla vehicle requested more amperage than it was capable of delivering. The outlet would always be able to draw up to but no more than 50A so NEC should be happy, the Tesla cable would just get the short end of the stick and leftovers.

But I guess gen2 HPWCs require logic in all units to coordinate.

 

[davewill]

.. The HPWC seems to be the cheapest EVSE on the market that does have this capablilty, b.t.w. I would be very happy to learn of a cheaper one.

-Snortybartfast

OpenEVSE can do it, but it's not really plug and play. You have to fool around with custom firmware. There are a couple of dual EVSE units out there that load balance, but they aren't cheap at all.

 

[israndy]

I watched a presentation this week of a fleet charging company that has a similar feature but instead of load sharing on a single branch circuit, it works to reduce demand charges when your entire draw is over a certain threshold. Demand shaving.

They use smart scheduling that takes not only who has the least amount of charge into consideration but also who will need the most range the soonest.

They also have a product for taking charge back from previously charged batteries to weather power outages and such. The whole time I was watching I kept thinking shouldn't there be a DC-DC way to balance the charges? One car is full, another car is empty. Just connect all the DC buses together thru current limiters and quickly get them all balanced. Probably NOT a good idea, but it was all I kept thinking about.

Wish I knew more about the physics of it.

-Randy

 

[Trips]

I have a ChargePoint Home installed in my garage. Has anyone created an attachment that you can hang up the cord with the J1772 adapter attached? It is kind of a pain to attached and remove the adapter every time you use it.

 

[israndy]

You should be able to use the Tesla one:

https://www.amazon.com/Tesla-Motors-1022771-00-A-Cable-Organizer/dp/B01EO5BCR6

I had a friend who has a 3D printer download one from Thingiverse and print it for me. Don't know the details

-Randy

 

[miimura]

You should be able to use the Tesla one:

https://www.amazon.com/Tesla-Motors-1022771-00-A-Cable-Organizer/dp/B01EO5BCR6

I had a friend who has a 3D printer download one from Thingiverse and print it for me. Don't know the details

-Randy

I was going to say the same thing, but I tried it first. I have the actual Tesla cable hanger and the J1772 portion of the adapter prevents it from latching in the way the Tesla handle does. Maybe one of the Thingverse versions would work.

 

[DanInSunnyFL]

I'd like to do something similar to TampaRich at our new house. I am very familiar with the labor side of running electric lines but I'm not intelligent about requirements so I'll ask here.

FlasherZ, I would like similar setup to Rich, but my HPWC will be located outside. I will probably feed the 50A breaker from the main panel (also outside). It has a run through conduit into the attic and then it's exposed. The HPWC & NEMA plug (possibly) will be outside, on a concrete block wall.

Questions:
1. THWN #6 because it's outdoors and 50A? 30' run.
2. With a rear feed the HPWC and the NEMA box do I need to run conduit? I plan on feeding down through the concrete block wall.

Thanks,
Dan

 

[DanInSunnyFL]

Anyone have advice on this?

Thanks

 

[PV-EV]

You can not run individual conductors without conduit. THWN is OK. #6 is what I would use.