Installing Two 40 amp EVSEs? A word of Warning

[Bassman]

Was at the Sacramento Electric Vehicle Auto Association meeting last week. The SMUD (utility) representative told a horror story where someone in South Sacramento installed two 40 amp EVSE in their garage without talking to SMUD and fried the subdivisions transformer and associated powerline wires. Cost SMUD over $40,000 to repair. They tracked the problem to the guy and warned him next time he would be paying for all the repair costs. So A word of warning. Most subdivisions are designed at the maximum capacity according to SMUD and adding an additional 20KW draw could be a major problem. So talk to your electrical provider before you add a significant increase to your draw (such as two new 40 amp EVSEs).

 

[yblaser]

If I have 200 A service and I draw less than 200 A, I don't see how I would be liable for the utilities poorly designed system with an apparent lack of failsafes. :shock:

 

[miimura]

I have 400 A service, but charging my RAV4 dwarfs the rest of my typical household use. The equivalent of 4 homes worth of load materializing out of nowhere is a big deal for the utility. Of course, damaging more than just the one transformer serving his house is a little crazy, but we should not take our charging loads lightly.

 

[khaliss]

I have a 200A main panel, with a 100A subpanel that feeds two Clipper Creek CS-60s. The hardwired CS-60 has a 60A breaker (charges the Rav4EV), while the other CS-60 has a 40A breaker on a NEMA 14-50 outlet (charges the Leaf). I still don't understand how (2) 40A EVSEs would cause the utility transformer to overload and burn... a household usually has at least a 100A service, so wouldn't that trip if the owner was drawing over 100A?

 

[TonyWilliams]

I have a 200A main panel, with a 100A subpanel that feeds two Clipper Creek CS-60s. The hardwired CS-60 has a 60A breaker (charges the Rav4EV), while the other CS-60 has a 40A breaker on a NEMA 14-50 outlet (charges the Leaf). I still don't understand how (2) 40A EVSEs would cause the utility transformer to overload and burn... a household usually has at least a 100A service, so wouldn't that trip if the owner was drawing over 100A?

Heck, my two two air conditioners and electric dryer pull about 100 amps. Never been warned not to run them or the transformer might go "poof".

Then, throw in two electric ovens and the Rav4 at 40 amps.... I must be a transformer killer!!

 

[yblaser]

Yeah, my RAV4 and 40A EVSE has a peak draw of at least 3 times anything else in my house, and I certainly understand that can be an unanticipated load for the utility. The problem is that their equipment wasn't protected from such a failure mode and they (if accurate) tried to blame and intimidate their customer. While his actions could have led to the failure, the failure is certainly not his fault nor would he be liable.

To me at least this sounds like a story a utility guy likes to tell and while based on an actual event strays far from what actually happened.

 

[miimura]

Obviously I don't know what happened in South Sac, but when I was setting up my account with PG&E for my new construction, I was talking directly to an engineer who is responsible for making sure their infrastructure can handle the load demands from specific customers. Basically the gist was that they don't oversize service transformers because people generally don't drastically change their load. He took a complete list of all my appliances and we discussed future EVs. He is actually the one who suggested I get a 400 amp panel. I really had to twist the electrician's arm to put it in, but he finally felt it was justified after I told him I was doing solar in addition to the two future EV outlets.

As long as you tell the utility when you bring new loads online, they will make sure everything upstream can handle it. About two weeks after I moved in to my new house, they replaced the pole-mounted transformer serving my house and my two neighbors with a new and significantly larger one. Throughout construction they just fed the temp power pole and my permanent service through the old transformer.

 

[khaliss]

If they allowed our house builder to put in a 200A service panel, shouldn't that mean that PG&E specced our home to draw 200A max, doesn't matter what type of appliances/chargers/etc are running, right?

 

[miimura]

If they allowed our house builder to put in a 200A service panel, shouldn't that mean that PG&E specced our home to draw 200A max, doesn't matter what type of appliances/chargers/etc are running, right?

It means that your feed line from the pole to your meter must be sized for 200A service. Everything further upstream is PG&E's responsibility, to be upgraded at their expense, should you increase your actual load based on installed appliances. Most of the time, the load does not dramatically increase instantaneously, so they have some warning and can handle the situation. Like I said earlier, they are very careful to get an initial inventory of planned appliances for new construction. I'm considerably under my plan because I didn't install all the possible 240V loads that I wired the house for.

In any case, when you apply for the EV rate, they ask which car you have so that they can tell how much new power you may be pulling. I also went to the trouble and expense to get a permit for my EVSE install, even though I only changed the receptacle and hung the unit on the wall. That is also another opportunity for the utility to be notified of a new load.

 

[khaliss]

^ I see. Well, PG&E did send out a site engineer (when I requested for the E-9A rate plan) to perform a service inspection. So, I should be all good =)

 

[Bassman]

The point the SMUD rep was making was that you need to let the utility company know if you adding something that is going to add a significant draw. He said that most subdivisions have the transformer designed for the typical average home draw and not significantly more (probably a cost thing), which if you look at the typical house is less than 10KW draw at any one time (unless you have a Tesla or Rav 4 EVSE). Now while everyone is running their air conditioner, someone decides to charge both of their EVs with their 10KW EVSEs. Now you basically added two new households to their grid and bingo, the transformer for the subdivision blows. So, the moral of the story is "Let the utlity company know if you are installing something that draws as much as a whole house."

 

[khaliss]

^ Point well taken. I was hangup on my own little world (house) that I didn't think about how to look at things on a bigger picture (as how you explained it). =)

 

[jspearman]

I met a guy at the Nissan Leaf meeting back in January who has a Model S and a Roadster in his garage, so can't imagine what he's pulling from the wall if both cars are charging.

After reading this post I did check with APS to see if they have any special requests for EV drivers. There was only an email that said to contact if you had questions, so I guess APS is confident in their infrastructure.

 

[TonyWilliams]

I met a guy at the Nissan Leaf meeting back in January who has a Model S and a Roadster in his garage, so can't imagine what he's pulling from the wall if both cars are charging.

Roadster = 70 amps
Model S = 40 or 80 amps

 

[miimura]

I met a guy at the Nissan Leaf meeting back in January who has a Model S and a Roadster in his garage, so can't imagine what he's pulling from the wall if both cars are charging.

Roadster = 70 amps
Model S = 40 or 80 amps

Over 40 amps only with the appropriate EVSE like Clipper Creek or Tesla High Power Wall Connector. Roadster Universal Mobile Connector or Model S Mobile Connector are still only 40 amps, right?

 

[TonyWilliams]

I met a guy at the Nissan Leaf meeting back in January who has a Model S and a Roadster in his garage, so can't imagine what he's pulling from the wall if both cars are charging.

Roadster = 70 amps
Model S = 40 or 80 amps

Over 40 amps only with the appropriate EVSE like Clipper Creek or Tesla High Power Wall Connector. Roadster Universal Mobile Connector or Model S Mobile Connector are still only 40 amps, right?

Any of the mobile connectors (unless you build an OPENevse portable like I did) will be limited to 40 amps, since the concept was that you would use RV parks with 50 amp service.

Yes, only Clipper Creek (the Tesla Roadster "HPWC" is a Clipper Creek) and the Tesla Model S HPWC are over 40 amps. Only the Clipper Creek is UL listed.