Thought for a New, Improved UMC?

[Gig103]

Or just install a second outlet.

We have three NEMA 14-50 (used to be 2 and 1 6-50 I had swapped to 14-50)... A J1772 and Model S HPWC...

It's really not that big a deal. You can always lower the amperage on each car manually, if you're worried about drawing too much.

I can't speak for everyone, but a second outlet at my house would involve a subpanel, because I don't have enough space for a second double-pole 50A circuit breaker. And now we're talking 100A just for the garage, so I'd have to determine if the existing 200A service to the home is sufficient.

And from reading the HPWC page, it sounds like they "recommend" the 100A service to the garage to share multiple on the same circuit, where @OP was talking about a way to share 40A. I dunno if the HPWC would share the existing 40A load to two cars at reduced power.

 

[davewill]

... And from reading the HPWC page, it sounds like they "recommend" the 100A service to the garage to share multiple on the same circuit, where @OP was talking about a way to share 40A. I dunno if the HPWC would share the existing 40A load to two cars at reduced power.

It can do exactly that.

 

[DarkMatter]

In fact the HPWCs can share all the way down to a fifteen amp circuit for a shared twelve amp charge rate. That is really stretching the definition of "high power" though.

 

[MorrisonHiker]

In fact the HPWCs can share all the way down to a fifteen amp circuit for a shared twelve amp charge rate. That is really stretching the definition of "high power" though.

Maybe that's why they changed the name to just Wall Connector a while back? People here are just using old acronyms.

 

[Rocky_H]

Yet it went over most people's heads who gave him all sorts of two outlet options. Not good to do an accountant. Their head could explode.

It is a little irritating when people just ignore that part of the question or just skimmed and didn't notice it. People so flippantly throw out there "just" adding another 50A circuit, in addition to the first.

The people suggesting that probably have 400A or 600A total service to their homes. This question is obviously much more relevant to people who were able to fit in one additional 50A circuit, but probably not another, such as my house, where the entire service to the home is 125A. I'm not going to pay thousands of extra dollars to upgrade the feed from the street to my house to "just" put in another 14-50.

So @cpa yes, the new wall connectors are made to do this. Since you mentioned not getting how that works, here is what they do:
You do have to get two of them. You run a line from one 50A breaker in your main panel to a junction box or subpanel, where you can split the connection to each one of the wall connectors. You run a twisted pair of signal wires between the two wall connectors so they can communicate. Then, there are switches inside to mark one with the provided current of 40A, and that makes it the "master". The other one gets the switch set as "slave". They can dynamically shift charging amps between one or two cars, and the master/slave setup will make sure they never exceed the 40A that they are allowed to provide.

 

[Akikiki]

Yes, its a little irritating when people just ignore that part of a question or just skim over the details. And its also a bit frustrating when people don't recognize the difference between another 14-50 outlet and an additional 50 amp circuit. Adding another outlet on the original 50 amp circuit would provide the owner to two cars to plug both in using each car's UMC at the same time. This makes it easy and saves the owner from remembering to visit each car and unplug from #1 and then plug it into #2 so each can charge overnight.

Having the second/extra 14-50 outlet on a single 50 amp circuit would provide for both cars to be plugged in at the same time/same visit to the cars. Then each car can be configured to start charging at different start times allowing a breather before the second one starts its charge time (from each car's center console). Maybe this helps those folks that were not quite visualizing the opportunity two 14-50 outlets on the same circuit would be simple and cheaper than another charging cable/connector.

I'm the guy that's always looking for a way out of the corner before the door shuts. I've considered installing a HPWC/WC even though I only have a 50 amp circuit, and saving/leaving my UMC in the car. But my thinking is; I've heard stories on the forums where a WC seems to have a problem after working a while. Things can go wrong, and if a wired WC fails, you can't charge at that circuit, - that is, unless there's also a 14-50 outlet wired into the same circuit. So, if you can picture this, there's the HPWC/WC hardwired into a junction box and next to it is a 14-50 outlet box. If the WC had a hiccup, and does not appear to be charging, I can simply pull the UMC out of the trunk, plug it into the car and see if it charges. Now, I have more info to work with. I can begin to isolate where the problem is. In this scenario I was using the WC on a 50 amp circuit, so I was not really getting the full benefit of it being a 100 amp circuit, so I would be better off with having the 14-50 outlet than having the WC hardwired in to a box. If I had extra money to buy the WC, I think I would buy another UMC, so I could use one on the 14-50 outlet and leave one in the car. This also provides me a backup charging cable that if the UMC used daily has a hiccup, I can easily swap it with the car's UMC to see better where the problem is. Just my two cents.

 

[Rocky_H]

And its also a bit frustrating when people don't recognize the difference between another 14-50 outlet and an additional 50 amp circuit. Adding another outlet on the original 50 amp circuit would provide the owner to two cars to plug both in using each car's UMC at the same time.

I recognize the difference, but many inspectors consider that a violation of NEC and won't approve it. That's why people don't suggest it.

 

[davewill]

... Adding another outlet on the original 50 amp circuit would provide the owner to two cars to plug both in using each car's UMC at the same time. This makes it easy and saves the owner from remembering to visit each car and unplug from #1 and then plug it into #2 so each can charge overnight.

Having the second/extra 14-50 outlet on a single 50 amp circuit would provide for both cars to be plugged in at the same time/same visit to the cars. Then each car can be configured to start charging at different start times allowing a breather before the second one starts its charge time (from each car's center console). Maybe this helps those folks that were not quite visualizing the opportunity two 14-50 outlets on the same circuit would be simple and cheaper than another charging cable/connector. ...

Honestly they ignored it because it's a really bad idea, and they probably couldn't believe that was what was suggested. One little slip up, and you're tripping a breaker (if you're lucky). There's no way it would pass inspection.

Please do not do this. If you don't want to do two new WCs so that you can safely share the 50a circuit, then split the circuit into one 20a (6-20) outlet and one 30a (14-30) outlet and get the appropriate adapters. Then let the cars charge at the same time.

 

[mspohr]

This is what I installed ... a dedicated HPWC and another NEMA 14-50

View attachment 203026

I don't think this meets code.
It looks like you have a 14-50 socket and a HPWC on the same circuit. Even if it is wired with 6 gauge wire and 100 amp breaker, I don't think you can have two high power devices on the same circuit.
Hopefully this is wired with two separate circuits and two breakers.

 

[Canuck]

I don't think this meets code.
It looks like you have a 14-50 socket and a HPWC on the same circuit. Even if it is wired with 6 gauge wire and 100 amp breaker, I don't think you can have two high power devices on the same circuit.
Hopefully this is wired with two separate circuits and two breakers.

What if the dip switches are set to 40 amps for the HPWC. The 14-50 draws 40 amps, so both total 80 amps. Would that not meet code with 6 wire and 100 amp breaker?

 

[gregd]

You have to have all the components match. I'm installing a new circuit in the garage for my Roadster, which is capable of charging at 70 amps, s I pulled #4 wire to handle the higher current. But my EVSE is an OpenEVSE which has a 14-50 plug on it, so the wall socket is 14-50 to match. I asked, and the electrician said they could only do a 50 amp breaker, in spite of the thicker wire, because the 14-50 socket can't handle more than that. Only if I upgrade to a higher power EVSE, AND get it hardwired to replace the socket, can I upgrade to a bigger breaker.

If you want to share the single circuit between two cars, something needs to protect the 14-50 socket from a device that might want to suck more than 50 amps (40 continuous) through it. If the single circuit goes to a sub-panel with a separate (smaller) breaker for each of the charging ports, that can work too. Simply setting dip switches on the device that plugs into it is not sufficient because someone can swap it out or change the switches, and bad things could happen after that without the circuit breaker tripping.

 

[cpa]

It is a little irritating when people just ignore that part of the question or just skimmed and didn't notice it. People so flippantly throw out there "just" adding another 50A circuit, in addition to the first.

The people suggesting that probably have 400A or 600A total service to their homes. This question is obviously much more relevant to people who were able to fit in one additional 50A circuit, but probably not another, such as my house, where the entire service to the home is 125A. I'm not going to pay thousands of extra dollars to upgrade the feed from the street to my house to "just" put in another 14-50.

So @cpa yes, the new wall connectors are made to do this. Since you mentioned not getting how that works, here is what they do:
You do have to get two of them. You run a line from one 50A breaker in your main panel to a junction box or subpanel, where you can split the connection to each one of the wall connectors. You run a twisted pair of signal wires between the two wall connectors so they can communicate. Then, there are switches inside to mark one with the provided current of 40A, and that makes it the "master". The other one gets the switch set as "slave". They can dynamically shift charging amps between one or two cars, and the master/slave setup will make sure they never exceed the 40A that they are allowed to provide.

Thanks, Rocky! This entire thread could have been wrapped up with your answer, and we could have avoided some of the distraction.

 

[Evbwcaer]

Try googling, "Dryer Buddy." They might have a product, or make one, that would allow two UMCs to share a 14-50.

 

[msnow]

Thanks, Rocky! This entire thread could have been wrapped up with your answer, and we could have avoided some of the distraction.

The third post in this thread from @ecarfan said the same thing.

 

[Rocky_H]

The third post in this thread from @ecarfan said the same thing.

Yes, it was first mentioned there, but then @cpa said this:
"I looked at the HPWC that was referenced above. For the life of me I do not understand what it accomplishes. I still only see one plug in the illustration. I would expect something more like the Hydra."
So it seemed to need more explanation of how it works to accomplish that functionality.

 

[TR5642]

Thanks for your replies. I mentioned in the original post that there will be some people who will not or cannot install another receptacle. I just thought it would be handy for many folks in those situations. If there were such an item, Tesla could substitute this device for the conventional UMC for a few more bucks.

I looked at the HPWC that was referenced above. For the life of me I do not understand what it accomplishes. I still only see one plug in the illustration. I would expect something more like the Hydra.

The HPWC trick requires a separate HPWC for EACH Tesla you want to plug in at the same time. But when wired correctly, one becomes master and the other(s) slave, communicating to share the draw UP TO the limit specified in the master. HPWCs can be set for the circuit they are wired to whether that's a special 100A, a more conventional 50A or 60A or even a low current circuit (desperation to avoid increasing the main house capacity?) Leave the UMC in the car for when you need it away from the house and spring for the HPWC at home. They used to be crazy expensive but are now actually the same as a UMC and quite competitive with 3rd party wall units.

 

[timk225]

Anyone who can afford 2 Teslas can afford to have two 14-50's installed. How complicated does this need to be?

 

[miimura]

Anyone who can afford 2 Teslas can afford to have two 14-50's installed. How complicated does this need to be?

This will be more of an issue when the Model 3 is out. I certainly understand the reluctance to spend thousands of dollars for a panel and service upgrade.

 

[Rocky_H]

Anyone who can afford 2 Teslas can afford to have two 14-50's installed. How complicated does this need to be?

The word is not complicated; the word is expensive. If your house electric feed does not have the capacity to add two additional 50 amp circuits, that can cost who knows how much to pay the electric company to run a new line to your house, depending on your location and distance from the street. That can mean bulldozers, backhoes, trenchers, and maybe tens of thousands of dollars. So maybe people would be able to afford it, but it might not be worth the money just for some faster charging.

 

[DarkMatter]

So in that case they should install two Wall Connectors set up to load share.