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Is this the correct way for a European 3 phase Open EVSE?

Hello all;

I'm about to purchase a few OpenEVSE's to install chargers at home, at work and build a mobile one like the Fivari charger. I believe I've looked at everything available online for research, however there's no one source to show how a 3 phase, Euro spec OpenEVSE could be done. Some people have done it but nothing is absolutely clear. In order to not lose any functionality I came up with this, what I believe would be the true way of wiring an open evse with a 3 phase power network.

Some notes;

- Using the AC Relay to power the 4 pole European contactor with 220VAC coil. I don't think there are any contactors with this much power handling, using 12V DC coils. I hope this is the correct way to wire.

- Using the OpenEVSE built in GFCI for GroundCheck success and also using an external RCD to protect for all three phases.

- To see energy consumption in the LCD, I am putting only a single phase through the current measuring CT, this will only show amperage per phase.

- AC test's both (L3-L2) goes to exit of contactor so it would sense 220V AC on both test terminals (in ref. to ground of OpenEVSE board, otherwise 400VAC between both phases, I don't know how it is done) and auto sense Level 2. I hope I am correct with this logic.

Besides the wiring, for this to function properly I believe I need to do firmware modification such that;

- Level 2 nominal voltage for energy calculation should be 220V instead of 240. Also I need to multiply measured L3 current through CT by 3. (for 3 phases)

- To plug the mobile version to single phase 220V schuko, I'll connect only L3 and leave L1-L2 empty. That won't change a thing on the functionality side as EVSE doesn't tell between a single or three phase but in terms of measuring it shouldn't be multiplied by 3. So, I am thinking because this will be Level 1 charging, Level 1 energy calc. formula shouldn't be x3 measured current. It would be great if I could change the names from Level 1, Level 2 to "Single Phase", "Three Phase"

- I also would like to change the language of the LCD menu.

Do these make sense? Is this the correct way to wire? Could anyone direct me towards some links to edit the firmware properly? (I don't know much programming)

Thanks in advance for your help.

Wiring looks good. Only change would be to remove GFCI coil. It is not needed when a RCD is used. The ground check is done with AC_Test lines.

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One more change. The relay coil should be connected directly to both AC_Relay terminals on the OpenEVSE. No external connections are necessary as N and L1 will be switched through the AC_Input connection.

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Thank you for replying. How will the ground check work? Would it work connected as in the diagram I posted originally? As I've said I'm thinking of connecting both AC test to hot wire downstreams for auto detect L2 charging as if they were two 120V hotwires in a 240 setup. Any idea on where to start the language change, changing L1 name to single phase and L2 name to three phase and according energy, power calculations? Thanks!

Ground works by confirming at least one of the test lines has AC flowing from AC_test to ground. You could use the L1 and L2 detection as P1 and P3. 

To change the Language edit strings.cpp here is a small example:

#if defined(BTN_MENU) || defined(SHOW_DISABLED_TESTS) 

const char g_psSettings[] PROGMEM = "Settings";

const char g_psSetup[] PROGMEM = "Setup";

const char g_psSvcLevel[] PROGMEM = "Service Level";

const char g_psMaxCurrent[] PROGMEM = "Max Current";

const char g_psDiodeCheck[] PROGMEM = "Diode Check";

const char g_psVentReqChk[] PROGMEM = "Vent Req'd Check";

#ifdef RGBLCD

const char g_psBklType[] PROGMEM = "Backlight Type";


#ifdef ADVPWR

const char g_psGndChk[] PROGMEM = "Ground Check";

const char g_psRlyChk[] PROGMEM = "Stuck Relay Chk";

#endif // ADVPWR


const char g_psGfiTest[] PROGMEM = "GFI Self Test";

Has anybody considered R4 and R22 on OpenEVSE board? 

I tested my OpenEVSE board in a 3Phase setup, and damn those resistors get hot!!!

I am using OpenEVSE V4 where R4 and R22 are 47k, but the same problem would happen on OpenEVSE V5 as well even though R4 and R22 are 200k.

Unfortunately R4 and R22 are designed to take in up to 220VAC, and 380VAC is too much for them to handle since the resistors are not designed to dissipate that much power.

Has anybody countered similar problem?

Should I just go ahead and get resistors with higher power rating to solve his issue?


The 47K ohm resistors also have a diode to block power in one direction, each resistor goes from line to ground for a total of 230v in you setup. 47k at 230v divided by 2 is just over 0.5 watts. The resistor on the board is a 1 watt flameproof resistor.


The 330k ohm resister with blocking diode consumes 0.08watts in your setup, this resistor is a 0.5watt flame proof resistor.

Both setups have quite a bit of margin over the parts value. We have not seen very few failures in the field so replacement is not likely necessary. Upgrading to a v5 would cut the consumption of the test circuits by 0.42 watts.

Thanks for your explanation.

I fed 380VAC to AC_TEST port by connecting L1 and L2 output of 3Phase power contactor. I used two thermal measuring devices(a FLIR camera, and a Fluke thermometer), and both devices show the area near AC_TEST port gets around 100 degrees Celsius hot! 

What could be the problem then? I am confused!


Connect AC_Test 1 to L1 and the AC_Test 2 to N. 

I wish I could do that. Unfortunately I'm getting 380VAC out of a step-up transformer that doesn't have a neutral tab. 

I monitored the temperature on those resistors, and once they reach 110 degrees Celsius, they stabilize at that temperature and don't rise anymore. As long as that's normal then I'm OK with it, but if that doesn't seem right, then I will have to fix it.

I understand moving to OpenEVSE V5 and having a neutral tab would reduce losses, but I am using my last OpenEVSE V4 on hand, and will use V5 in future projects.


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