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Gen 3 HPWC 208v Commercial Install Question

Ilguy

Member
Jan 22, 2020
50
22
Chicago
I have a newly installed gen 3 HPWC at my business. We have commercial 208v service and I have a 60A breaker installed. There is significant distance to the parking lot install location. The HPWC is set for a 60A breaker. When I hook up my '20 MX, I'm seeing 23/mi/hr, 199v and 36/36A. The car will not let me turn AMPS up any higher than 36A when at this location.

This same car at my house (220v/48a) with a gen 3 HPWC gets 48A charging without any problem.

From what I've found posted, the 208v commercial service and distance may be the reason for the slower charge speeds at work. Does this sound right?
 

jmaddr

Active Member
Mar 29, 2019
1,033
1,053
Florida
There is significant distance to the parking lot install location.
Define "significant"....and define the wire size
Distance most definitely affects voltage drop and load amperage. It think it's best to consult an electrician and tell them you need to support a 48A load at the end. They many need to bump up the wire size (and at a "significant" distance, the cost to do that may be a bundle. In the end, 2003V/6A and 23 mi/hr is not all that bad).
 

Tessaract

Member
Aug 12, 2019
337
338
Ottawa
I have a newly installed gen 3 HPWC at my business. We have commercial 208v service and I have a 60A breaker installed. There is significant distance to the parking lot install location. The HPWC is set for a 60A breaker. When I hook up my '20 MX, I'm seeing 23/mi/hr, 199v and 36/36A. The car will not let me turn AMPS up any higher than 36A when at this location.

This same car at my house (220v/48a) with a gen 3 HPWC gets 48A charging without any problem.

From what I've found posted, the 208v commercial service and distance may be the reason for the slower charge speeds at work. Does this sound right?
Yes, I think you're right. The 199V while charging most likely causes the car onboard charger itself to limit at 36A for reasons that would require the designer to comment.
 

Ilguy

Member
Jan 22, 2020
50
22
Chicago
Further examination indicates they accidentally used 8 AWG instead of recommended 6. I'm guessing that will make a big difference. Will be re-done in 6 soon.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,035
8,644
Boise, ID
Quoting the end first:
Further examination indicates they accidentally used 8 AWG instead of recommended 6. I'm guessing that will make a big difference. Will be re-done in 6 soon.
I see you found your answer. Yikes! Using 8 gauge on a 60A rated circuit is a really blatant violation of code. That's pretty disturbing.

But onto the original questions:
The HPWC is set for a 60A breaker. When I hook up my '20 MX, I'm seeing 23/mi/hr, 199v and 36/36A. The car will not let me turn AMPS up any higher than 36A when at this location.
That specific number of 36A does tell what is going on. Tesla instituted a safety measure some years ago, where it measures the voltage at the start, with no load, and then when it ramps up the current to start charging, it also measures how much the voltage sags. Within a few volts, it's fine, but if it drops too much, it will reduce the maximum current to three fourths of the current you were originally set for and try again and see if it can use that with less voltage drop. So 36 out of the attempted 48 is three fourths and does show that it saw too much voltage drop and triggered that safety system.
 

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