1412 and 1413 are definitely in the NVM (SAF and EAF settings for LOW fan speed), so avoid using it too often 
Also, if 12113 and 12114 wont work for CO2/RH readings - try using 12112 and 12113 respectively. These by the way do not go into NVM (as well as any other sensor reading)
Ok, so if I manage to get the unit to adjust its own speed based on the CO2 value I give, Ill be fine? It will also save me from many of my automations 
12112 worked
Thank you, this should make my automations way easier
Now that I can remove some of my automations, how do I use my VAV the best way using the internal automations of the ventilation unit? (keep in mind that I dont have a display, only modbus).
I tried changing 1273 to “VAV” but then the fans just stopped. I guess there is some more settings I need to configure?
@PatrickJanson apologies for delay in reply, vacation
VAV does not work because I assume you have no pressure sensor inputs configured, what you’d have to do is configure the pressure sensor inputs for Supply and Extract sides and override the sensor inputs over modbus.
I am not in the office for another two weeks so I hope this can wait - I can provide detailed instructions once back in the office.
I hope it works for you!
No problem, the ventilation unit already works alot better
Hello everyone, I’m new with SAVE unit and I’m glad for this topic. I own SAVE VTR150 unit which should be controlled via HA. I already bought actuators to control supply air to all rooms with air supply (living room, bedroom, children’s room). Actuators should be controlled by CO2 detectors in each of these room. To reach static pressure in system I also have VAV conversion kit. My idea is to find fan speed which covers my needs with small reserve and if needed, I can turn the unit off (I also have actuator on supply and exhaust air so it should be save). Is it good way to control the system this way?
As I mentioned, I have actuator with emergency function to close valve when the unit will be switched off. I bought Shelly relay to control this actuator by HA, but the Shelly relay can be also controlled by switch. Is there some contact on the unit which came on/off depending on status of unit? If so, I could leave control of the actuator on SAVE unit.
EDIT:
RTFM 
Anyway, SAVE controls supply/exhaust valve by 0/24V and switch on Shelly relay expects 110-230V. So one option is another relay or I will control valve by HA automation.
Thanks to @DariusSystemair for the notification about NVM. Could you please send us which registers are saved to NVM? Hope it’s not hundreds of them 
Thank you in advance for all advice.
Hello @rickard1, I bought Elfin EW11A as you recomended, but I can’t get working with SAVE unit. I can see that request from HA goes thru EW11A to SAVE unit, but I cannot get any reply from SAVE unit. I have same configuration in EW11A and in modbus settings in SAVE unit, but still no reply. Could you please share you settings?
EDIT: I already solved this issue. Problem was that saving of EW11A is a bit tricky and sometime helps reset device multiple times. Also is good to export current settings in XML to check what is actually in settings.
BTW How did you reach to have EW11A on static IP. I can get it working on DHCP, but when I try to set static IP, the EW11A is unreachable and not visible on router settings. I have to hard reset it then.
I do DHCP reservation for the EW11As IP-adress in my DHCP server.
I do not use stativ IP-adress.
Is there a way to write to the room temperature?
I tried address 12103, but it doesnt look like it wants to update.
I would really like to get this to work to be able to stop the freecooling when the room is cold enough.
I do the same as you.
but i just turn of freecooling when desired temp is met.
- name: vtr250_frikjoling
unique_id: vtr250_frikjoling
address: 4100
slave: 1
command_on: 1
command_off: 0
write_type: holding
verify:
Thank you. It was plan B, but first choice was to set static IP directly on device
I have issue too with System Air VTR 500.
I use this configuration :
modbus:
- name: VTR500
# See https://www.home-assistant.io/integrations/modbus/
type: tcp #User setting
host: 192.168.9.105 #User setting
port: 8899 #User setting
timeout: 3 #Timeout for slave response in seconds (default=3)
delay: 2 #Time to sleep in seconds after connecting and before sending messages (defualt=0)
message_wait_milliseconds: 50 #Increased to hopefully reduce errors in my serial comm (Default:30 for serial connection, 0 for all other connections.)
climates:
- name: vent_VTR500
unique_id: vent_VTR500
address: 12102
slave: 1
scale: 0.1
offset: 0
precision: 1
max_temp: 30
min_temp: 15
temp_step: 1
target_temp_register: 2000
…
It newer worked. 
As I see bytes moving on serial port, I assume bound rate is correct.
Maybe some ideas what to check ?
change baudrate to 9600, its the minimum you can go
Did you change it in the ventilation units setting under modbus also?
No, there sits 115200. Shell I change it ?
yes, this values needs to be identical
Well it was 115200 on vent unit, I have tried to have same on EW11 before - no success. Now changed both to 9600, still not ok.
Then you have a wiring issue or other issues with your rtu to tcp converter
Well its very strange
I see tcp port open :
Nmap scan report for 192.168.9.105
Host is up (0.0060s latency).
Not shown: 998 closed tcp ports (conn-refused)
PORT STATE SERVICE
80/tcp open http
8899/tcp open ospf-lite
Device is running, and wiring kinda ok, based on someones post upfront.
Even EW11 shows HA connected from proper IP address:
Configuration points to proper ip and port:
If I turn off EW11, Ha gets “Unable to connect” error. So per theory communication between EW11 and HA - works fine. I believe its something about addresses. Maybe VTR500 have different ones. MODBUS_FOR_RESIDENTIAL_D24810_USER_MANUAL_EN__A007_.PDF (systemair.com)
