40 Amp being decreased to 30A

[SPF]

Hi - Crowdsourcing for help:

I live in a condo and my deeded ground floor space is wired to my electric panel in my unit on the 8th floor. The 240 outlet is wired to a 40 Amp circuit. My electrician connected a Gen 2 HPWC and I keep getting the Amperage decreased to 30 A and I get error messages:
“Charge rate reduced. Check for an extension cord or faulty wiring”. My personal electrician feels there is a nick or other issue with the wiring. The developer claims,

“
There is a 40 amp breaker with #8 wires used for this dedicated outlet. Furthermore we tested the outlet and lines with no evidence of a defect or damage to the lines. We also checked the voltage in the 8th floor electrical closet and found the same results as we did in the garage. Both tests showed no voltage drop or any damage to the wires. Therefore we determine there are no defects with this dedicated line.

i.e., the wires used have no nicks nor was there any voltage drop. After completing these tests, we determine there are no defects in the electrical line or connections. ”

please help! I’m on a time crunch for this!

i really appreciate it!

 

[SPF]

I forgot to note, the charge rate should be 22mph, but at times I’m getting only 8mph. As I have two Gen 2 HPWCs, I had both installed and am experiencing the same issue with both wall chargers.

 

[Sparrow]

To get 40amps to the car you need a 50amp breaker. You can only charge at 80% of the breaker's rating.

You are also losing some charging speed since your input voltage is 205 and not 240 like you would have at home.

 

[Pluturi]

I see a couple different issues. One, you say it’s a 240V service, but the car is showing 205V. That is a big drop, so perhaps your building is wired as a three phase commercial building and actually only gets 208V and not 240V. That would explain part of the charging rate difference. Second, the HPWC only runs at 80% of what the circuit is capable of, so if it is a 40A circuit then the maximum you will get is 32A. Not sure why 30A vs. 32A, but could be due to the voltage drop. Reconfigure the charger to only pull 32A and see what happens.

 

[SPF]

I see a couple different issues. One, you say it’s a 240V service, but the car is showing 205V. That is a big drop, so perhaps your building is wired as a three phase commercial building and actually only gets 208V and not 240V. That would explain part of the charging rate difference. Second, the HPWC only runs at 80% of what the circuit is capable of, so if it is a 40A circuit then the maximum you will get is 32A. Not sure why 30A vs. 32A, but could be due to the voltage drop. Reconfigure the charger to only pull 32A and see what happens.

Thank you for the reply - much appreciated. Quick Question: On the Tesla screen, shouldn't it read 32A and not 30A typically? Also, do you feel the Voltage drop could be due to faulty wiring?

 

[Sparrow]

Not sure why it is reading only 30amps. As you say it should be 32. Have you tried setting your car to 32amps and see if it goes there instead. Maybe it is some kind of Tesla software thing that is dropping it an even 10amps below your request. Not likely, but may be worth a shot.

As to the voltage, does your condo provide 210 voltage instead of 240? I am certainly no expert, but I think alot of businesses get 210. I forget the technical reason for 210 instead of 240.

 

[Pluturi]

Not sure that it is faulty, but maybe too long. You say it is wired from the 8th floor to the garage. How far is that? You could expect a 4V drop in 100 feet of 8 AWG.

 

[P85_DA]

Not sure why it is reading only 30amps. As you say it should be 32. Have you tried setting your car to 32amps and see if it goes there instead

OP ..this above ..not sure why no one mentioned earlier

 

[tes-s]

Sounds like your electrician may have installed the HPWC incorrectly. Correctly configured, it should show a max of 32a.

You said you got a message that the charging rate was reduced to 30a - reduced from what? If it was reduced from 40a the HPWC is not configured properly.

Your charge rate will vary, even when the car shows 30a 205v - notice the different mi/hr in your different pictures. That is because the 30a 205v is the power going into the car, and the charge rate (and calculated time remaining) is power going into the battery. AC takes away from power going to the battery.

 

[SPF]

Not sure that it is faulty, but maybe too long. You say it is wired from the 8th floor to the garage. How far is that? You could expect a 4V drop in 100 feet of 8 AWG.

I'm guessing it's about 150 -200 feet.

 

[SPF]

Not sure why it is reading only 30amps. As you say it should be 32. Have you tried setting your car to 32amps and see if it goes there instead. Maybe it is some kind of Tesla software thing that is dropping it an even 10amps below your request. Not likely, but may be worth a shot.

As to the voltage, does your condo provide 210 voltage instead of 240? I am certainly no expert, but I think alot of businesses get 210. I forget the technical reason for 210 instead of 240.

Thank you - per my contract I was told it would be wired for 240V 40A; however, not sure if it truly was wired for 240V.

 

[ElectricIAC]

Voltage sag likely causing too much resistance to even pull 32A like you should be on a 40A breaker.

Wire seems a bit on the thin side for a run that long as well which is probably contributing to your voltage sag.

 

[Rocky_H]

There is a lot of not correct stuff in here so far. @tes-s has the source info right. The wall connector was not configured right for the circuit level. Or you could say the wrong circuit rating was installed.

1. Voltage: Yeah, this isn't a 240V building. It's a multi-dwelling condo or apartment kind of place, so I'm sure it's got the 208V from 3 phase. 205V on your display would be totally normal at the end of a pretty long wire run like that.

2. Wire: They used 8 gauge wire? That would be appropriate for a 40A circuit. Technically that might pass for a 50A if it's wire in conduit, but not a good idea at all for that long a run.

3. Dumb electrician: I have seen this way too many times. It's amazing how common this is of electricians not understanding this is a constant load. That's a little bit understandable because most residential electricians don't ever deal with appliances that are constant loads. Ovens, dryers, microwaves, pretty much anything else a resident would use are all intermittent, so they are allowed to use 100% of a circuit rating. So I have seen this exact situation many times on both Tesla forums. The electrician hears the car should get 40A feed, so they wire a 40A rated circuit, thinking that's correct. They don't realize it has to be 40/50 or 32/40.

4. Explanation for the 30A: This is a monitoring and safety feature Tesla put in several years ago. It checks the voltage at the start, and then when it ramps up the power, it will check if there is excessive voltage drop, indicating some kind of resistive wiring or connection issue, and it will drop the current level down to three fourths of what it was using. That's the clue that indicates it's this issue. If it's 3/4 of your rate, it's because it triggered this voltage drop detection safety system.

Resolution: You got a 40A circuit. That wall connector just needs to be reconfigured for a 40A circuit, so it will only try to feed 32A maximum.

 

[Rocky_H]

Oh, so I forgot to vote in the poll.
No, the wire is not damaged, but what you have is undersized for the load that was trying to be drawn from it and was causing too much voltage drop.

 

[mxnym]

3. Dumb electrician: I have seen this way too many times. It's amazing how common this is of electricians not understanding this is a constant load. That's a little bit understandable because most residential electricians don't ever deal with appliances that are constant loads. Ovens, dryers, microwaves, pretty much anything else a resident would use are all intermittent, so they are allowed to use 100% of a circuit rating. So I have seen this exact situation many times on both Tesla forums. The electrician hears the car should get 40A feed, so they wire a 40A rated circuit, thinking that's correct. They don't realize it has to be 40/50 or 32/40.

I'm not going to scold you for saying dumb, because here's the thing: The electrician doesn't have to realize or understand that the load is constant if he simply reads and follows the HPWC manual when connecting it.

 

[Rocky_H]

I'm not going to scold you for saying dumb, because here's the thing: The electrician doesn't have to realize or understand that the load is constant if he simply reads and follows the HPWC manual when connecting it.

You could go that direction...
Hmm, the rest of my comment became irrelevant. I had typed out how he should know from NEC that all electric vehicle charging equipment is now defined as a continuous load no matter what. But that was in the 2017 update to code. And I just checked where Illinois sits with respect to what version they are using. They are not on the 2017 version. Nor are they on the old 2014 version, even. They are still on the 2008 version!! Ugh.
https://www.ecmweb.com/national-ele...2884/nec-adoption-where-does-your-state-stand

 

[DSolie]

Open up your Gen2, and make sure the rotary arrow is pointed to #6, that tells the HPWC that you are on a 40amp circuit.

**Make sure to power OFF your HPWC before you open it or change any settings**