4 HPWC daisy-chained-proper config

[yerEVan]

I did some searching here but didn't find exactly what I'm looking for, so here it is.

At our office, they kindly added Tesla Chargers, which is great. However, I believe they completely messed up the configuration. I'll keep the story brief as to not put you to sleep, but my question is: What is the proper configuration for 4 HPWC's in a row?

When they hooked up the 4 HPWCs, they did it incorrectly (electrician who clearly did not know what they were doing). So when I went out to charge for the first time to test it with the Building Maintenance guy, it did not work. Red/Orange light on all 4. So I went to the instructions and sent the page to the Maintenance person that showed how to fix that error, and he gave it to the electricians, and they fixed it. Great. Green lights.

Plugged it in and charging started. Awesome! Only got 30Mph. Not bad as the only car charging.

However, my colleague plugged in his Model 3 (both 3's) on the far HPWC (3 away from me), and we both got 15Mph.

Next person plugged in and we all got anywhere from 3-8Mph. Clearly this is not ideal, and something is wrong.

I asked to see the breaker box to see how they wired it, and all 4 units are on a single 100a breaker. I told him this is probably not right. Wrote an email explaining to the building that if a 4th person plugged in, we would all get nothing at all.

They said it was hooked up correctly per the electricians. The same electricians that didn't even realized their first install was not working (red light) until I told them how to resolve.

Anyway, damn, this is kinda a long statement, but my question is, what is the optimal config for a 4 bank HPWC? clearly not the way it is, because only 2 people can charge at a time where it's even worth it.

Thanks

 

[MorrisonHiker]

It sounds like they installed it correctly. With the 100 amp breaker, the four wall connectors can provide a maximum of 80 amps of output. We have three wall connectors installed at home on a 100 amp breaker that provides 80 amps. If we charge one car, it can use 48 of the 80 amps (11.5 kW). This is due to the 48 amp limit of the charger in the car. Other Teslas might only have 32 amps, 40 amps, 72 amps or 80 amps, depending on what charger they have installed. If we charge two cars at once, then each gets 40 amps (9.6 kW). If we we have three cars charging at once, they each get 26 amps (6.2 kW). As each car finishes charging, the load is balanced out for the remaining cars that are still charging.

Your install at work is most likely commercial and using 208 Volts instead of 240 Volts so it can probably provide 10 kW for a car with a 48 amp charger, 8.3 kW to each car when two cars are charging, 5.5 kW each for three cars and 4.1 kW each for four cars.

The main point of having the daisy-chained wall connectors is that they allow the wall connectors to share the breaker. If each wall connector had its own breaker, then they wouldn't need to be daisy-chained. That would require a higher capacity service panel and higher amp service and cost a lost more to install than daisy-chained wall connectors.

MPH isn't helpful since it varies depending on the car and charger. Can you give use the details on how many amps you are seeing when charging alone? Also, we need to know what year and model car you have in order to determine what charger you have and what it is capable of. If you get 48 amps when charging and your car has a max of 48 amps, then everything is set up correctly. If you are only getting 40 amps when charging alone and your car is capable of 48 amps, then there might be an incorrect setting on the master wall connector.

 

[DOCAL]

Optimal in terms of charging speed would be 4 separate 100A breakers, with 1 HPWC on each.

However, that's a lot of power to potentially pull, so the electricians would have to perform appropriate load calculations and determine if that is the best option overall.

You would have to check the manual for the units you have, but if they'e the same as mine then with the current wiring they should set 1 charger to be master, with its switch set to the D position (100A breaker, 80A output).
The other 3 should be set to F (slave mode).

Given that you are able to load share, it sounds like they've set 3 to be slave, but probably have the master set to a lower output current. You said you're testing with Model 3 cars, I'd guess they have it set to something like a 40A breaker rather than 100A.

If the company will allow you, you could probably turn the breaker off and check this yourself.

 

[yerEVan]

I would think that 3-8Mph with 3 cars out of 4 potential, is really not good. that's basically 30+ hours to charge your car if it's below 40%. if someone turns the heat on, then you are getting pretty much 0Mph.

I think what i mean is, they should have had 2x80a breakers 1 for each pair. If you have 4 chargers, you are assuming up to 4 cars to charge. and if 4 cars charged, none would get any power. also, when 1 is plugged in it gets only 30Mph, which means probably max Amp is set to 40 in the master?

and thank you both for the input thus far.

 

[Rockster]

Four chargers on one 100-amp breakers is perfectly correct. As others have said, that just translates to 20 amps each if all four vehicles are charging. 240 volts at 20 amps is still 4.8 kW (or if it's three-phase power it's more like 4.2 kW), which should translate to more than 3 mph, though.

 

[yerEVan]

Four chargers on one 100-amp breakers is perfectly correct. As others have said, that just translates to 20 amps each if all four vehicles are charging. 240 volts at 20 amps is still 4.8 kW (or if it's three-phase power it's more like 4.2 kW), which should translate to more than 3 mph, though.

OK, so something is wrong with the dip switches or something else in there. so if it should be at worst 4.2 that's 15Mph if 4 cars are charging without AC or Heat on. But currently it's 15Mph when 2 are charging. Meaning, 30Mph when 1 is charging which says they have the master set to the wrong Max Amperage of probably 40amps in the Master.

I think that's it. And thanks all for the input, i'm walking over to the guy now so i can let him know.

 

[Rockster]

Yeah, on a 100 amp circuit the master should be set to 80 amps and all the rest should be slaved.

 

[yerEVan]

ok, so in the instructions, i see it says this on page 29. So they may have set it correctly. I'm unsure why it says 1-8 instead of 1-D. Are you not allowed to have it set to D when doing Master/Slave scenarios?

Set one Wall Connector as the master by setting the Rotary Switch Position from 1 to 8 depending on the maximum available output current. Set up to 3 Wall Connectors as slaves by setting the Rotary Switch Positions to F. In the load sharing network, only one unit can be designated as the master (refer to Set the Operating Current on page 21).


https://www.tesla.com/sites/default...a-wall-connector-installation-manua-en-v1.pdf

 

[MorrisonHiker]

ok, so in the instructions, i see it says this on page 29. So they may have set it correctly. I'm unsure why it says 1-8 instead of 1-D. Are you not allowed to have it set to D when doing Master/Slave scenarios?

Set one Wall Connector as the master by setting the Rotary Switch Position from 1 to 8 depending on the maximum available output current. Set up to 3 Wall Connectors as slaves by setting the Rotary Switch Positions to F. In the load sharing network, only one unit can be designated as the master (refer to Set the Operating Current on page 21).


https://www.tesla.com/sites/default...a-wall-connector-installation-manua-en-v1.pdf

That looks like a typo. It is allowable to set it from 1 to D. In your case, the master should be set to D. Sounds like they might've only set it to 8.

If they correctly set it to D, then older Teslas with 72 and 80 amp chargers would be able to charge a lot faster. Also, all 48 amp charger cars would get to charge 20% faster, assuming it's only set to 40 amps currently.

 

[brkaus]

Do make sure they actually wired each of the units with large enough wire to support 100A.

How did the split the 4 units off of the single breaker?

 

[yerEVan]

Do make sure they actually wired each of the units with large enough wire to support 100A.

How did the split the 4 units off of the single breaker?

great point. i'm unsure. everything is buried, but i will ask them for sure before they change anything. simple enough to find out though. appreciate the follow-up.

 

[LCR1]

Yep looks like they read the instructions on page 29 and set it to the maximum of 8, when it should say 1-D as indicated on page 21.