FoxESS Community - Owners & Installers Forum

Posted: **Sat Nov 01, 2025 6:56 pm**

Hi,
this is my first post, so I wanted to say hello.
I recently bought a P3-12 inverter and want to integrate it with Home Assistant. I want to make sure how to connect the wires to the Elfin WE-11A. I connect the pins from the EMS485A COM connector (PIN 13) to connector A on the EW11A, and PIN 14 of the EMS485B to connector B on the Elfin.
Where should I get the power supply? Can pin 10 (12V+) and any of pins 18, 19, or 20 (GND) be used as power? I've read that external power supplies were recommended in previous inverters due to the weak 12V+ socket (300mA). What are your recommendations? What settings should I configure in the Elfin and the inverter next?
Can I use a 2x0.75 two-core copper cable to connect the inverter to Elfin or does it have to be twisted pair?
Regards, Szymon

Posted: **Sun Nov 02, 2025 4:50 pm**

Szym3k wrote: ↑Sat Nov 01, 2025 6:56 pm Hi,
this is my first post, so I wanted to say hello.
I recently bought a P3-12 inverter and want to integrate it with Home Assistant. I want to make sure how to connect the wires to the Elfin WE-11A. I connect the pins from the EMS485A COM connector (PIN 13) to connector A on the EW11A, and PIN 14 of the EMS485B to connector B on the Elfin.
Where should I get the power supply? Can pin 10 (12V+) and any of pins 18, 19, or 20 (GND) be used as power? I've read that external power supplies were recommended in previous inverters due to the weak 12V+ socket (300mA). What are your recommendations? What settings should I configure in the Elfin and the inverter next?
Can I use a 2x0.75 two-core copper cable to connect the inverter to Elfin or does it have to be twisted pair?
Regards, Szymon

Hello,

Yes you are correct with connecting COM port EMS485A to A and EMS485B to B on the EW11, you don't need a GND connection as this is a differential pair.

On the power supply there is 12v and GND on the COM connector but they are relatively low power (less than 300mA), I don't use the Elfin myself but I know a few people that do and they have found that an external 12V 1A power supply is the most stable way of powering the Elfin EW11 device.

On the cable, if it is a short run (a couple of meters) then 2 core copper cable is ok, but anything over that you should use twisted pair or re-use an old cat5/6 network cable, cut the connectors off and use a similar coloured pair (i.e. green, white/green or blue, white/blue etc..)

Look here for the configuration https://github.com/nathanmarlor/foxess_ ... Elfin-EW11

FoxESS Community - Owners & Installers Forum

Connecting the P3-12 inverter to Home Assistant.

Connecting the P3-12 inverter to Home Assistant.

Re: Connecting the P3-12 inverter to Home Assistant.