Using UMC vs HPWC for all charging at home

[Cottonwood]

Wouldn't this be against code? I could see it being overlooked by some inspectors, but on a large scale it shouldn't happen.

I don't think that there is a code problem as long as the range that is being supported only needs a maximum of 40 Amps as an intermittent load. One electrician that I spoke to said that this is a pretty common installation to save a few dollars on wiring costs.

It would be a code problem if the intended purpose of the 14-50 were to support EV charging at a continuous load of 40 Amps. Then the 125% of continuous requirement hits, and 40 Amps time 125% is 50 Amps, so you need wire and breaker rated to 50 Amps.

 

[linkster]

Wouldn't this be against code?

Nope. Money talks.

For the reasons Cott just stated.

 

[davewill]

Wouldn't this be against code? I could see it being overlooked by some inspectors, but on a large scale it shouldn't happen.

There isn't really a 40a outlet to choose, so there isn't anything else to do, really.

 

[jerry33]

Wouldn't this be against code? I could see it being overlooked by some inspectors, but on a large scale it shouldn't happen.

Ovens don't count as a continuous load (they cycle on and off), so it shouldn't be against code.

 

[FlasherZ]

Wouldn't this be against code? I could see it being overlooked by some inspectors, but on a large scale it shouldn't happen.

No, perfectly legal to wire a range receptacle with a 40A breaker. A 50A receptacle doesn't mean it's backed with 50A conductors and/or 50A breaker/OCPD. Welders, for example, can be legally wired with a 6-50 receptacle, backed by a 30A breaker and a 20A conductor (there's a special article for welders). Motors can be wired the same.

NEC ref 210.21(B)(1) and 210.21(B)(2).

Technically, you could use a 15A breaker with 15A conductor and a 50A receptacle, if it were the only receptacle and the only loads connected to it were less than 15A. If there are multiple receptacles on the circuit, then you're limited to table 210.21(B)(2) which only allows 50A receptacles on 40A or 50A circuits.

The rules basically say that a) conductors must be rated for the load to be served; b) a breaker must be chosen to protect the conductors against overcurrent; c) all equipment and terminations must be rated for the load. If the load is a 8 kW range, then a 40A breaker is sufficient. Appliance nameplates determine requirements - you'll typically see them say things like "minimum circuit conductor size", "minimum circuit ampacity", "maximum breaker size", etc.

Technically, plugging your UMC into a 40A range circuit is where the code is violated, because by default the car with its 14-50 adapter requires a 50A circuit rating, despite the fact the user can turn the current down (there's a difference between installer-configured settings and user-configuration that would reduce current). It's usually a moot point because there won't be an inspector to stop you.

 

[wayner]

Tesla is sending replacement UMC to Canadian Model S owners - see this thread: New UMC?

 

[thecloud]

Tesla is sending replacement UMC to Canadian Model S owners - see this thread: New UMC?

Even as a US owner, I've been following that thread with interest. It spurred me to order a second UMC last week, rather than waiting until later when a 40 amp version might no longer be available for purchase.

The new UMC (ordered as a US configuration) and its accompanying 14-50 adapter seem to be identical to the ones that originally came with my car. The connector does not have the new-style charge port button mentioned in the Canadian thread. The only difference I noticed is that the storage bag has been upgraded with a second zippered pocket and Tesla logo, which my old one didn't have. The car recognizes 40 amps with the new 14-50 adapter.

One UMC now stays plugged into the NEMA 14-50 outlet in the garage, while the other lives in its bag in the trunk with all the adapters, so I don't forget to take it with me as my trip destination charger. I also wanted the second UMC as a backup in case either one fails down the road. (The HPWC was not really an option because it's a permanent installation and my panel can't supply more than 40 amps on a 50A breaker.)

I can certainly see why Tesla might decide to limit the UMC to 32 amps, as the unit and adapter get very warm when drawing 40 amps continuously. I already limit my normal overnight charging to 32A at home for this reason. But if I need to be on my way quickly, the faster I can charge, the better.

 

[mknox]

Even as a US owner, I've been following that thread with interest. It spurred me to order a second UMC last week, rather than waiting until later when a 40 amp version might no longer be available for purchase.

I was going to get a second UMC a few months ago (to leave at home) and was told by my Service Center that they were no longer available for sale in Canada. Now we know why.

The HPWC was not really an option because it's a permanent installation and my panel can't supply more than 40 amps on a 50A breaker.

I ended up getting a HPWC for home. At the end of the day, it was only something like $100 more than a UMC would have cost, and makes for a nice clean installation. Not sure if you know, but there are DIP switches inside and you can configure the HPWC to go on 15, 20, 30, 40, 50, 80 or 100 amp circuits. What I did is set the DIP switches for 50 amps and wired it to a NEMA 14-50 cord, then just plugged it in to the existing 14-50 outlet.

 

[Cottonwood]

I ended up getting a HPWC for home. At the end of the day, it was only something like $100 more than a UMC would have cost, and makes for a nice clean installation. Not sure if you know, but there are DIP switches inside and you can configure the HPWC to go on 15, 20, 30, 40, 50, 80 or 100 amp circuits. What I did is set the DIP switches for 50 amps and wired it to a NEMA 14-50 cord, then just plugged it in to the existing 14-50 outlet.

The few that I have dealt with came with the DIP switches set to a 50 Amp breaker and 40 Amp charging.

I've seen multiple instances of installs of an HPWC on a 100 Amp breaker only offering 40 Amps of charging; the solution was always to set the DIP switches to the higher current 100/80 setting instead of the default 50/40. Many installers don't read the installation manual...

 

[mknox]

The few that I have dealt with came with the DIP switches set to a 50 Amp breaker and 40 Amp charging.

I've seen multiple instances of installs of an HPWC on a 100 Amp breaker only offering 40 Amps of charging; the solution was always to set the DIP switches to the higher current 100/80 setting instead of the default 50/40. Many installers don't read the installation manual...

That's an interesting observation. I've come across many that are set up for 40 amp charging (and a couple even less). I just assumed that's all the capacity they had and set it up accordingly. I never considered improper setup. I honestly can't remember what my factory settings were, but I thought it was set up for 100 amps. It's fuzzy because as part of the setup you have to put it in Test Mode first, then set the switches to the proper amperage.

 

[FlasherZ]

That's an interesting observation. I've come across many that are set up for 40 amp charging (and a couple even less). I just assumed that's all the capacity they had and set it up accordingly. I never considered improper setup. I honestly can't remember what my factory settings were, but I thought it was set up for 100 amps. It's fuzzy because as part of the setup you have to put it in Test Mode first, then set the switches to the proper amperage.

My original HPWC shipped with the switches in test mode to begin with, and it simply wouldn't work unless you followed directions!

The new ones are shipping with 40A current configured by default. I just opened a new one and looked.

 

[AmpedRealtor]

My original HPWC shipped with the switches in test mode to begin with, and it simply wouldn't work unless you followed directions!

The new ones are shipping with 40A current configured by default. I just opened a new one and looked.

I've also noticed many destination chargers top out at 40A. I wonder how many of them didn't bother to flip the right switch?

 

[mknox]

My original HPWC shipped with the switches in test mode to begin with, and it simply wouldn't work unless you followed directions!

The new ones are shipping with 40A current configured by default. I just opened a new one and looked.

Hmmmm... I definitely remember having to flick the DIP switches to get it into Test Mode, so maybe mine was factory set to 40 as well. Having it come already in Test Mode makes a lot of sense!

 

[Nigel Tufnel]

My 50 amp dedicated circuit outlet is mounted "upside down" which I'm told can contribute to connection problems due to the weight of my UMC. Can any idiot rotate it, or should I call an electrician? I currently (no pun intended) charge with the cord suspended on a wall hook next to the outlet. Seems to work fine when I remember to use it.

 

[FlasherZ]

My 50 amp dedicated circuit outlet is mounted "upside down" which I'm told can contribute to connection problems due to the weight of my UMC. Can any idiot rotate it, or should I call an electrician? I currently (no pun intended) charge with the cord suspended on a wall hook next to the outlet. Seems to work fine when I remember to use it.

It's pretty easy to rotate the receptacle. Turn off the breaker, pull the cover, unscrew the 2-4 screws holding the receptacle. Looking at the wires, one direction should look better than another to rotate (CW vs. CCW). Rotate 180 degrees, same screws in the same locations, turn the breaker on and give it a test.

 

[aus]

Anyone have any insight on battery degradation charging at 32A vs. 50-100A?
I've read here Supercharging often will damage the battery, but haven't seen anything regarding low or high home charging effects on the battery?
.

 

[FlatSix911]

Keep in mind that Tesla has produced two versions of the HPWC with different dip-switch settings.

 

[ArtInCT]

Keep in mind that Tesla has produced two versions of the HPWC with different dip-switch settings.

FLAT: Do you happen to know the approximate date that the second version of the HPWC was introduced?

 

[jerry33]

Anyone have any insight on battery degradation charging at 32A vs. 50-100A?
I've read here Supercharging often will damage the battery, but haven't seen anything regarding low or high home charging effects on the battery?
.

Both are so low compared to battery capacity that I doubt there is any practical difference (there may be a measurable difference if the measuring devices are sensitive enough). The main degradation is the amount of degradation on the UMC or HPWC when used at full capacity, not the battery pack.

 

[FlatSix911]

FLAT: Do you happen to know the approximate date that the second version of the HPWC was introduced?

Yes, the HPWC version 1.0 was introduced in 2012 (model number last digit A, B or C) and version 2.0 was 2014 (model number last digit D).

The new 2014 HPWC revised the settings and eliminated the 60A/70A/90A choices and replaced them with lower power 12A/16A/24A options

Original 2012 HPWC ------------------------------------------------------------------------------> New 2014 HPWC