HPWC problem

HPWC problem

I had my HPWC (gen1) installed a few years ago on a 60 amp breaker and it was happily charging my old car (3/16 build) at 40 amps which was all the car could handle. But my new (3/17) car has a 72 amp charger and it also charges at only 40 amps ;-( So I took the cover off the HPWC and saw that the dip switches were set for a 50 amp breaker (no idea why it wasn't set to 60 all along) so I changed the setting to 60 amps and then the car only was drawing 12 amps!!! I can't understand why this would be as there isn't even a setting in the documentation for a 15 amp breaker. Anybody have any ideas?

Aerodyne | 10 maggio 2019

Something is not happy obviously. Have you checked the trouble shooting section of the HPWC manual, as well as the setting instructions for the dip switches? Is seems as though it is defaulted to the minimum 12a as a precaution.

Aerodyne | 10 maggio 2019

BTW, Max current on the 60A breaker is 50A per code. That is for sure.

steveg1701 | 10 maggio 2019

Actually, I thought it was 48 for a 60? And yes, I did check the dip switch setting instructions

murphyS90D | 11 maggio 2019

The rule is 80% so yes the max for a 60 amp breaker is 48 amps. Did you remove power from the unit while changing the dip switches? Most items that have set once dip switches only read them when power is turned on.

steveg1701 | 11 maggio 2019

thanks murphy, did that as per the documentation!

bp | 11 maggio 2019

When changing the DIP switches, did you disconnect the car before powering off/on the HPWC and did you press and hold the RESET button for 5 seconds after turning the power back onto the HPWC? Also recommend you try setting the switches to the 40A (32A charging) and 50a (40A charging) positions to verify they work correctly.

steveg1701 | 11 maggio 2019

yep, did all that! Works fine with the 50 amp setting charging at 40 (didn't see any point in trying 40/32).

Anthony J. Parisio | 12 maggio 2019

Odds are the Electrican used 50 Amp wire not 100 Amp wire. I don’t know of a 60 Amp wire. 100 Amp wire is more expensive thicker and harder with which to work. The car might test for 60 Amps and not like what it finds.

Bill_75D | 12 maggio 2019

6 gauge copper is rated for 60 amps. It is also what is used for 50 amp circuits.

Anthony J. Parisio | 12 maggio 2019

Do you think Tesla might be playing it safe? Could it be looking for 100 Amp wire at 60 Amps? | 12 maggio 2019

Tesla doesn't look for wire size/type/ampacity - it monitors the voltage drop when it starts to draw power. As it increases the current draw, it the voltage drops too much, the car backs off on the amount of current it will draw. It's a great way to deal with undersized wire, poor connections and other problems external to the car - but it's also an indication that something is wrong and should be corrected.

In the industry, no one calls wire "50 amp wire". It's not too meaningful. It should be a gauge, materia (copper) and insulation type (NM, etc.). The electrical code then designates how much amperage the wire can handle. There are more variables too, such as the size of the conduit (if run through conduit) that may limit the current.

It's also safe (and sometimes desirable) to jump to a lower gauge wire than allowed. For example, while I use a 50 amp circuit, #6 gauge copper wire is allowed. I used #3 gauge wire which heats up less, meaning it is slightly safer, but also loses less power to heat over years of use. Probably not enough to pay for the added expense :) I mainly used a lower gauge to allow higher currents if I needed it in the future. Far easier to pay a little extra when the wires are run, than replacing the wires later at a much higher expense.

milesbb | 12 maggio 2019

Sounds like the HPWC is having problems reading the 60 amp dip sw setting. As a test you might try higher current settings 70 amp or 80 amp, of course limit the car charging to 48 amps.

steveg1701 | 13 maggio 2019


I figured the problem might be related to the bottom switch so I tried a couple of higher currents that required keeping that switch in the same position and got varying results less than 40. Then I tried setting the switches to 100 amps and made sure to set the in car limit to 48 (car has the 72 amp charger) and now it charges at the full 48 amps I had expected. I guess that the worst that can happen is that the car somehow forgets it's only allowed 48 amps and throws the breaker. Problem solved I guess ;-)

milesbb | 13 maggio 2019

@steveg1701, Sounds like you have enough proof that the problem is the wall connector, and likely the dip switch you are guessing is the problem. I would at least ask what Tesla would charge to repair this unit. If it was purchased with the car it should still be under warranty. If you do not want to return this unit it might be a simple fix for someone that does a bit of electronic repair. Could be a cracked solder at the dip switch, or the dip switch has failed to close internally. So re-soldering or adding a jumper could set the unit to 48 amp limit.

steveg1701 | 13 maggio 2019

not sure milesbb - I first thought the problem might be in dip switch #4 and so tried a higher setting that kept 4 in the same position it was when it worked at 50A and again got a much lower than expected output. The only setting that seems to work "right" for me is 100 and that has #4 in the opposite position as 50A. When I bought the HPWC (and the car) the standard charger was 40A and a dual charger upgrade was available to get 80A. These correspond to 50A and 100A on the HPWC and I find it a bit hard to write that off as a coincidence!