Hi Per,
Thanks for your answer!
I guess you are from Sweden, me too.
Are these the products I need?
What programming are you using? This one?
Sorry for the delay Anders.
Yes, also in Sweden. I’ll keep it in English to be of help to others.
Our northern location keeps the pool life seasonal.
April = preparation time, pool opening in May if warmer air will cross the nordics. However April weather = snow this weekend 
10 steps back in the spring process.
HARDWARE with iSaver
Yes the ESP 32 board.
Not an expert but I have to flag that I’ve had issues with another models. There seem to be differencies in depending on chip structure and connectors. If you’re into details and have the knowledge of the ESP32 boards you might be able to figure it out.
However, I picked the AZDelivery ESP32 Dev Kit C V4 NodeMCU
Amazon SE Link to AZDelivery ESP32 Dev Kit C V4
The RS485 module
I guess most modules are ok to use. I picked this one
5 V MAX485-modul RS485-modul TTL till RS-485 modul konverteringskort kompatibel med Arduino
Amazon SE link to MAX485-module
Tip! I found the PCB Breadbord handy as I dont have a 3D printer to use
iSaver Inverter control with ESP32 + RS485
To help the ones that have limited knowledge.
AZDelivery ESP32 Dev Kit C V4 NodeMCU
MAX485-modul RS485-modul TTL till RS-485 (works with AZDelivery)
Make sure you have proper 5V supplier
Connectors in the i Saver are marked.
- IMPORTANT NOTE! Be aware of the Warrenty issues when opening your iSaver. On your own risk. Be careful and make sure you dont damage anything. BE SAFE and unplug the device when doing any work!
Tip - Connecing the Controller to the iSaver
Use an old Ehternet cable.
I wanted to have the option to disconnect the controller from the iSaver.
I recommend a Water safe RJ45 Ethernet connector with my controller. Picked a cable with outdoor RJ45 plug . Not as in this image that is annother indoor project but similar.
The ESPHome YAML
The iSaver dont use a standard RS485 protocol. There are several users that had issues with setting this up. However we’ve come to a point where its up and running and working pretty well.
Dont know what the next step would be. However there are some annoying error codes that pops up in the log for the ESPhome and it would be nice to improve the code to make that go away. However that might be difficult as the iSaver RS485 protocol doesnt follow the standards.
I can share my ESPHome setup yaml code to help you. Please go through the code and make the important changes to make it work in your network and home assistant.
@AndersLA that is a good one to use. A good start. Then you can build on your own design and functions to be useful for you.
I created a first UI version last year but I am planning on develop an improved UI design this spring.
I only have the ESP32Home Yaml code to share at this point. However that can be used with the UI that he created. MAKE SURE YOU MAKE CHANGES TO THE CODE TO WORK WITH YOUR SETUP.
Link to my Github with the YAML code vers 2025.10
First important functions created
- emergency stops
- increase circulatioins during specific hours based on electricity spot prices and other usage of electricity (charging car) Ellevios effect tariff charges, solar production, usage pool, time of day and prepering for heavy usage.
I want to take it to the next level, improve current functions and making it work more smoothly with other smart functions as when to
- increase rpm when water circulation goal for 24 is not met
- increase rpm when water needs more filtering after heavy use and auto dosing is working hard
- all smart triggers of auto programmes to be working better in junction with the other units like auto dosing, heater and UV-light
- User friendly UI control, better design
Example early version and look UI for heater.
Planning developing this into something better.
Thanks @kidnor Per for the detailed answer!
I live in southern Sweden so I already have 14 degrees in the pool without a heater. I’ve started setting the values now.
I’ve now ordered the stuff you’ve used and hope I can start fixing it next weekend.
My iSaver doesn’t look quite the same inside but I hope I can get it right anyway. I hope i can connect it here.
I have a G&J heat pump and use modbus to HA. Works great.
Yea, down south you’re futher ahead, several weeks. Hope you dont have to deal with storm Dave… We had enought of messy destruction already this winter. Great to hear that you’re getting started to get setup.
What is the model name on your iSaver frequency unit? Most of them seem to be the same inside, only a different brand on the box.
So are you using regular modbus control for othe heat pump?
The one we got has Tuya (local) and works OK, however its a bit annoying and I dont like to be depended on external services. Did found some connectors on the board and they all seem similar when it comes to the control board no matter what brand.
Let me know if you have any more questions when you’re about to set it all up.
/P
No damage in de storm! 
This i how i look inside my heat pump. Looks like it was similar on many as u say.
Use https://www.amazon.se/dp/B09PD5ZD56?psc=1&ref_=cm_sw_r_cp_ud_ct_GZS4AHA4Y0X3J88942E4 to connect to wifi.
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