Definitely, the modbus connection through F1/F2 is definitely easier. However, as you stated, you cannot access everything, and most importantly for my usecase, I couldn’t inject the ambient temperatures of each zone through F1/F2 only via the control layer F3/F4.
The hardware/software needed for
modbus: a computer, the snet software, a dongle to connect the F1/F2 wires to the computer
f3/f4: a computer (or a raspberry (single board computer)), the python script software, a dongle to connect the F3/F4 wires to the computer.
For the modbus connection, you could also replace the snet software with a custom script to connect to something external (MQTT)
Additional details. MQTT is a communication layer to unify internet of things, and to allow for multiple agent to grab those data and process them. I use is linked with Home Assistant (a glorified dashboard for IoT, with scripting/automation capabilities).
Here are some Home Assistant screenshots of my dashboard :
Many thanks, @Topaz, this looks interesting, but I’m a complete beginner with comms hardware/software, so please be patient with me…
Currently I import data from F1/F2 into my laptop via an RS485-to-ethernet adapter and a virtual port. When I hit “Monitor” on the virtual port I see loads of Hex messages coming in:
I presume these messages represent the various controller inputs/outputs which need to be interpreted for human consumption (at the moment SNET does this, sort of…)
Are you saying that if I install MQTT (I downloaded something called MQTT Explorer today) I can get it to emulate SNET?
Can MQTT record data as well as display it? (I haven’t tried setting it up yet - it looks quite daunting for a layman.)
Also are you saying that additional information is available at F3/F4 (like “EHS Input Power” which I see on your HA output, but which SNET doesn’t display)?
If I do need to switch to F3/F4 to get at this extra data, can I simply reconnect my existing RS485 adapter?
What does Home Assistant do that MQTT doesn’t? HA costs money and I don’t want to spend £100 on something I don’t need for anything else (we run a really low tech house - I don’t even own a smartphone…) If I do need something with HA’s capability, do you know of a lower cost equivalent?
HA is mainly a frontend of presentation of recorded data,
MQTT is just a virtual link to convey data from a source (rs485 interpreter, f3/f4 interface) to a sink (HA or whatever).
The main goal of HA is to allow for interaction made easy with the heatpump. It can run on the same host as you would run SNET. and it does record only for about 14 days or so (configurable, but it’s a very fat encoding), I usually install another tool to record longterm (influxdb).
I’m not sure transitioning from F1/F2 (RS485) to F3/F4 (modulated RS485) would be of any use if you already have all your usecase covered with the F1/F2 link.
Cheers
The only data I wanted that SNET-Pro2 doesn’t give me (from F1/F2) is the Outdoor Unit power consumption, and though this is available on the remote controller display, I can’t log it.
I guess I’ll just have to correlate Compressor Current (which I can log) against Outdoor Unit power consumption (seems to be roughly power (kW) = 0.42 x current (A) + 0.2) and stay away from F3/F4…
Dear Sarah,
If I’m not mistaken, I’ve found the total consumption in the F1/F2 communication, It’s issued from the CT1:
[0x8217, “VAR_OUT_SENSOR_COMPRESSOR_CT1”],
[0x8278, “VAR_OUT_SENSOR_OCT1”],
Check one of those, it should then be multiplied by 0.1 and to your local grid voltage.
Hope that helps, and clearly, it’s overkill to adopt a new data access chain just for one value!
Have fun
I don’t know how to access the 0xnnnn codes directly, but SNET-Pro2 displays an entry “OCT1” which I never understood, but if this is “Outdoor Current Transformer 1” as you hint in your post, then I can indeed get the data I’m looking for. I’ll fire up SNET tomorrow and see if it now makes sense…
My only question is, where does the 0.1 in your post come from?
Indeed it sounds like you get your intel there!
The 0.1 is because the value is expressed with a unit of 0.1A if I remember correctly.
I pray that this solves your problem.
Regards,
Unhappily, @Topaz, the “OCT” reported by SNET (supposedly, related to Outdoor Unit power consumption via grid voltage) bears little if any relation to the power consumption displayed on the remote controller.
Take a look at this plot of reported Compressor Current vs OCT (without your 0.1 factor, gathered over about 90minutes, during which time the compressor inverter varied 20-50Hz and the calculated heat output varied 4kW-10kW):
I have a question for @billt and/or @glyn.hudson.
I have bought the MRW-TA kit, fitted it and plugged it into the ROOM socket on the MIM board. How do I “activate” the new sensor? The display on the wired controller is still showing the temperature of the thermistor in the wired controller not the new remote thermistor.
For reference #2091 and #2092 are set to “NOT USE” and #2093 set to “Room Temp ON/OFF or WL Interlink ON/OFF (Water Pump3)”
I do not have a separate thermostat, the system is controlled the wired controller.
I’ve added an ‘@’ in front of Billt and Glyn’s names to convert them to what we call ‘at’-references. This way, they (particularly Glyn) will get notified of your question.
It’s a long time since I did it, but I think the steps are -
enter Service mode > Indoor Zone Options > Temp sensor selector.
You can toggle between local and remote sensors there.
Hi @billt
Thanks for your reply. Your suggestion has partially worked. The temperature displayed on the wired controller has changed from displaying that of the internal thermistor to a fixed reading of 20.0 C. Heating or cooling the new external thermistor doesn’t change the reading. This is the same problem you commented about on a different forum approximately a year ago. Unfortunately solution was given.
How do I get the actual temperature of the external thermistor to be displayed, rather than the fixed 20.0 C?
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I’m slightly out of my depth here, @SteveSpanners but I think that your MRW-TA counts as an “External Room Thermister” for the purposes of FSV settings, and as such, you should set FSV #2091 (or #2092, depending on whether you are using WL#1 or WL#2) to your preferred setting. Once done, FSV #2093 (which uses the wired remote controller) will be ignored.
I use a 3rd party (Honeywell) roomstat (i.e. I use #2091 rather than #2093), and I haven’t yet been able to see the current roomstat measurement indicated on the remote controller - all I see is a default 20degC. I assume that this is because the Honeywell doesn’t transmit the measured temperature, it only transmits “demand” or “no demand” signals into the MIM controller in accordance with its thermostat setting. (In the case of the Honeywell these are (variable cyclic) TPI signals, but the MRW-TA is most probably simply on-off.)
So unless you can discover a way of getting your remote controller to interpret and display the MRW-TA signals, you just can’t do this .
The MRW-TA is just a thermistor which replaces the thermistor in the wired remote. It isn’t an external thermostat so 2091 and 2092 should stay off. 2093 is set to 3 in my installation.
Sorry, I’ve run out of ideas and don’t remember what else I may have done.
(The remote thermistor does report room temperature to the controller and it is displayed on the remote and can be extracted with an RS485 interface.)
I have measured the resistance of the thermistor in the wired remote controller and the MRW-TA and they have similar characteristics. This supports what billt is saying, and contradicts SarahH saying it is an on/off device.
My understanding also agrees with billt that 2091 and 2092 should be OFF.
2093 is currently set to “Room Temp ON/OFF or WL Interlink ON/OFF (Water Pump3)”, I think I need to do some experimenting.
If I can’t find a “proper” solution, I think I will connect the MRW-TA directly to the wired remote controller by cutting out the existing thermistor and soldering the leads from the new remote thermistor in instead.
The MRW-TA kit appears to be normally used on aircon units, and the instructions supplied mention turning switch K1 off. I have tried turning off switch 1 of the red switch block on the MIM board, but it didn’t help.
I will investigate further and report back if I find a solution.
Thanks again.
and I don’t want to spend £100 on something I don’t need for anything else (we run a really low tech house - I don’t even own a smartphone…) If I do need something with HA’s capability, do you know of a lower cost equivalent?
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. Oh well, back to the drawing board…
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