Ebusd via a dongle. Have a look here:
Thanks a lot!!
Hi all,
Is it possible to run a wireless sensotherm monitor (without the wireless external temp senso) and use a wired external temp sensor?
It gets very cold here and I don’t want to rely on batteries for outside temp. But would like wireless monitor to save drilling and chasing.
I see the wired temp sensor is connected to its own port on the main computer, and the sensocomfort to the bus. So logic would say yes, but perhaps if I connect the wireless control to the bus it will override the wired connection (annoying) and look for a wireless temp sensor only.
I’ll try anyway if no one knows.
Thanks
Guys, I’ve got a cry for help.
I want to write up a hot water basic guide, but I’m struggling.
Because I use a Mixergy and everything is almost dealt with via their app, I would love some confirmation of my understanding of the vaillant settings and behaviour.
I’ve never had to use vaillant DHW target, schedules, cyl charging offset, hysteresis etc.
I’m looking on the likes of the Arotherm Facebook group and i’m not seeing consistent advice or behaviour.
So could we look at this for me please?
Cylinder Charging Offset does NOTHING
You can set it to 0K or you can set it up 10K, the same results
Same end flow temp, same end return temp.
I hear this on this forum, but I don’t see this mentioned anywhere else.
Has anyone done any day to day comparison of OEM I could look at?
Or a couple of different people do the same test?
Could we test this out fresh (some of the previous conversations were going back 3 years).
I don’t want to declare this and it not be right. LOL 
Next bit I need to understand.
a hot water cycle will only start within a defined schedule AND if Cly Charge Hysteresis is exceeded?
Let’s say your Cly Charge Hysteresis is 5K
And your single charge schedule is 1pm to 4pm.
Even if your Cly Charge Hysteresis goes above 5K (so temp drops more than 5C at say 8pm), the water re-heat will not start until 1pm the next day?
Similarly, if we get to 1pm and the Cly Charge Hysteresis is only 3K, no hot water re-heat will start?
Another option, rather than use a small schedule is to be ‘always on’.
Either by setting hot water mode into manual or setting a schedule 00:00 to 23:59
and then relying Cly Charge Hysteresis to fire reheats whenever required.
Hope that all makes sense.
Ta, Mick
Yes I’ve got a hardwired external temp sensor and wireless sensocomfort and it all works as expected.
Your understanding is entirely correct in all aspects.
Charging offset is completely ignored and is - as far as I see it - only in the controller as a leftover from other heaters (gas probably).
Your hysteresis understanding is also correct.
I am personally running with “always on” (no schedule) and a hysteresis of 20K (maximum). This hysteresis never triggers for me by itself. Once a day, on the forecast warmest hour, my cylinder target temperature is increased to 70°C for 1 minute via Home Assistant to trigger a recharge (because my tank is alway colder than 50°C the hysteresis fires when switching target to 70°C). After 1 minute I reset the target to my typical 47°C and the DHW cycle stops as soon as this is reached.
Happy to do experiments if needed, but this is my understanding.
Perfect thank you!
Thanks Andre
I love a proper test on this? I’d even quote / reference the runs in the new article for evidence if someone could this?
Perhaps we could put the results in this thread for reference?
Haha, another hacker. Does anyone run their hot water just via the Vaillant controls!?!??!!?
Sure! Good thing I implemented the DHW temperature display that’s now also on emoncms.org 
, as this will be extra helpful. Have your pick looking at the data with either the central NTC10K sensor installed in the tank that’s used by the Vaillant controller or my self-installed sensor at the top of the tank.
Charging offset was set to 20K up until yesterday, I just set it to 3K, so this afternoon’s run will feature the new offset. I also switched the hysteresis to 15K and disabled my automation, so the automatic start will happen anytime soon. Let me know whether I should do any more experiments in the name of science 
.
My Heatpump App with central DHW sensor (tank default, used by Vaillant controller)
My Heatpump App with top DHW sensor (self-installed DS18B20)
Weather-based DHW control is such a low hanging fruit for efficiency boosting, why wouldn’t I do it?! 
Amazing Andre, thank you.
And I assume of this is backed up via ebus data too? 
I find it amusing the sensocomfort manual says
Cylinder Charging Offset:: “Desired temperature + offset = flow temperature for the domestic hot water cylinder.”
When it does NOT
a) change the target temperature
b) change flow temperature in any way
The hot water process is very straightforward.
- It chooses the compressor speed from the hot water mode chosen (Normal, Eco etc) and sticks with it throughout the run
- It starts the process at the flow temperature of the water it finds and ramps up the temperature until it’s heated the water and the probe matches the target.
Flow temp might go higher than target depending on location of probe?
and DT between flow and return? Does it click off once the return hits target?
DHW Target temperature and current temperature for the tank (center) both come directly from ebus –> NodeRED –> emoncms, so this is exactly what the Sensocomfort sees. What other ebus evidence would you like?
You can run the heat pump without a Sensocomfort and have it use its own internal logic. In the manual for my VWZ (indoor unit/controller) there is no mention of the offset, so that’s why I think this is a feature only used for other end devices.
Yes, compressor speed is constant, 50 rps for Eco here:
There is no involvement of flow temperature in the control system here at all. It starts the compressor at the given speed and sets the flowrate as defined in the DHW settings. The resulting flow temperature increase is purely a “passive” effect of how much power the compressor outputs vs. how much the DHW cylinder with its heat exchanger can extract. If my heat pump provides 10 kW and my heat exchanger takes 7 kW of that and delivers it to the tank in the cylinder, then the remaining 3 kW increase the water temperature in the DHW coil loop over time.
The control mechanism is simply “Compressor at desired speed until DHW tank sensor reaches the target temperature (47°C for me)”. In that way it’s just like a very simple water boiler thermostat that switches off once the setpoint is reached. You could not build a “dumber” control mechanism .
There is one safety feature here in that once flow temperature reaches around 70°C, compressor speed is ramped down and it is turned off once flow temperature reaches around 75°C. This is data from a legionella cycle where the backup heater takes over to provide the last few degrees. You can see the compressor ramp down from 50 to 30 rps towards the end.
Flow temp always goes above the desired DHW target temperature, so does return. As above, they don’t enter into the control scheme. DHW temperature itself also slightly overshoots as the compressor is turned off in the instant the temperature hits target and then the remaining energy in the DHW loop diffuses into the tank.
DT is constant for me throughout the cycle at around 4K. Return temperature also is not considered in the control mechanism and is simply a result of the constant compressor speed and energy exctaction by the heat exchanger.
Amazing, all makes sense.
I will dumb all that down into words my expected target audience will understand.
Looking forward to the article!
Two questions then
If the schedule time ends (say 1pm to 2pm), does the hot water run just stop at 2pm, even if target temperature is not reached?
Similarly, if the max cycle time is reached (say 60 mins), the hot water run just stops, even if target temperature is not reached?
These two, along with ‘target temperature’ reached are the three ways a hot water run can stop?
I’ll send you a preview when I’ve fully drafted it up.
I seem to recall this happened to me when I still had a schedule - I will retry.
Yes.
There’s also some setting for a min time between DHW cycles so the next one cannot start before this time has passed from the last run.
I see around 370watts on a regular basis once it has settled down (6kw aerotherm +). Obviously, only in the shoulder periods before winter really sets in. Still cycles about twice an hour. Everything in Eco mode as this makes it a LOT quieter, barely audible even up close.
Sensocomfort
Is it really not possible to transfer settings from one sensocomfort to another? This seems insane for the cost of it all. Vaillant software really is poor.
Mine was installed with a wired unit and I got a second hand wireless to run instead but when connecting it up it was all fresh.
Yep, most ASHP controllers are from the Stone Age, with Vaillant’s being one of the ‘better’ ones…
The app is much better and once you have the internet gateway installed there’s no real reason to touch the Sensocomfort anymore (apart from installer settings).