Vaillant vSmart - Any experts out there?

[AndriiPin]

Your problem sounds similar to what we experienced until Vaillant replaced the whole vSmart kit (i.e. the wiring control centre, communication unit and room thermostat) under warranty at the end of 2019.

Until that point, the heating curve made little difference to the flow temperature being requested over the eBus (D.009). However, since the kit was exchanged under warranty, our vSmart has been behaving as expected, meaning that if there's a big room temperature rise requested (say +2°C when the heating comes on in the morning) the flow temperature is higher (often about 55°C), but if it's just being asked to maintain the room temperature the flow temperature is nearer 41°C.

When our replacement vSmart was installed the heating curve started off at 2.6. We've resisted the temptation to fiddle with it, and it's automatically reduced itself down to 1 and now 0.6.

Vaillant's technical people were at a loss to know why our system wasn't behaving properly. However, it seems to have been a hardware problem, as it now works well.

Thank you for such a prompt reply

I have written off the Viallant headquarters because the local and national support in my country has proved themselves useless. They claim that this is the way that smart thing works, but somehow I suspect them of being totally unaware of the way it is designed to work! It seems to be an unprofessional attitude that you may never expect it from such a reputable brand. Shame on them. I hope that the central office will shed light on my issues and give my local provider a solid kick in the butt.

Your system does work fine because it doesn't require you to adjust a heating curve or anything else. Since my system is under warranty till July this year, I have enough time to creep up on Vaillant Ukraine and become their nightmare!

I will keep you posted here on my progress. Maybe there are or will be other poor souls suffering from similar issues.

 

[Matthew B]

Another autumn, and the same problem has returned!

Since October our vSmart (number 3) has been requesting silly eBus target temperatures again (often in excess of 80°C when it only has to raise the temperature by 0.2°C and the outside temperature is 10°C). We've resorted to limiting the flow temperature on the boiler to a maximum of 40°C, which stops the radiators getting unbearably hot and reduces the room temperature overshoot (up to a degree). Howver, this is what the vSmart is supposed to do without our intervention. That's why it's so expensive to buy!

Interestingly, our vSmart has never caused the boiler to "modulate" as shown in the video in my first post. It only ever switches the boiler on and off. Once the boiler has fired up, the vSmart never reduces the target temperature. We've never seen anyone else post a comment that the vSmart doesn't modulate the flow temperatures, so we have a nagging concern that there's something wrong somewhere in how something's set up, and we're the only people in the world with this problem. Any thoughts?

 

[Harry Bloomfield]

My one niggle with my Vaillant 407F system, is that I like to have night (16C) and day temperatures (18C) set in auto somewhat lower, then adjust manually on the display to a temporary higher temperature (21C Day). What is supposed to happened is that if I temporarily change the temperature, I then have to press 'OK' to make save it as its stored temperature.

What I find is that it will randomly store my temporary change as a new stored temperature. It seems to second guess me and after I have tweaked the temperature up a few times, it decides that is what I really want stored.

 

[Janko32]

Matthew,

when i read your first post i thought I wrote it. After that I read the whole conversation. You have an identical problem that I have. I am from Croatia. I bought an Eco TEC 386 (or something like that, 38kW max power) in February 2020 and when it was set up everything worked great, exactly like you wrote it should work after you replaced everything with a warranty. After the summer I returned the settings to winter (true, I installed an extra radiator in the garage and in doing so the service technicians had to turn off the boiler). Starting in October and after these works the whole system behaves like on/off, therefore. When the temperature needs to be raised by approx. 0.5C it sets the flow temperature to 70C (I allowed him that much on the boiler). At the same time I see that the eBus asks for 80 app. Only time when I noticed that it modulates anything is when it maintains the room temperature (for example at 20C and then flow goes in the range 55-60 which is still too much). My house is as well insulated as yours. Just like with you, it never modulates the flow temperature but only the flame intensity once it reaches the max set flow temperature on the boiler. For example, when the night starts, the room temperature automatically drops from 20 to 18.5 and once it reaches that low temperature, the system heats up again to 70C and exceeds the set temperature by 0.5. But if it's asked to maintain 20 during the day then it exceeds it by only 0.1-0.3. I have never achieved that modulating that shoud work for most of the time at 40-45C flow. Even today I am not sure what the problem is. I don't want to change the flow temperature on the boiler (now at 70) because then the system doesn't work what it should because it is expensive and like you said it should do it for me. Just like with you heating curve makes no impact. I can set it to 0,8 or 3,0 makes no impact.

 

[Pete the Feet]

Funnily enough I've just been trying to fathom how the heating curve works. With the commercial systems that I have previously had experience of, the heating curve worked as follows. Outside temp 0C flow temp 80C. Outside temp of 20C flow temp 20C [Off]. A heating curve of 3 will give a 3C rise of flow temp for every degree C under 20. For example outside temp of 15 will give (5x3) + 20 = 35C. Outside temp of 5C will give (15x3) + 20 = 65C. Freezing at 0C or below will give (20 x 3) +20 = 80C

Altering the curve will give something similar to the desired temp for boiler. However I think the inside temp may have a bearing on this to prevent overshoot/hysteresis. This final part is the mystery to me. perhaps the curve is based on 21C as opposed to 20C as this is the temp that is used in many domestic heating calculations.

I have the self learning mode set to off on my set up as our hours of occupancy are variable.

 

[Janko32]

Another autumn, and the same problem has returned!

Since October our vSmart (number 3) has been requesting silly eBus target temperatures again (often in excess of 80°C when it only has to raise the temperature by 0.2°C and the outside temperature is 10°C). We've resorted to limiting the flow temperature on the boiler to a maximum of 40°C, which stops the radiators getting unbearably hot and reduces the room temperature overshoot (up to a degree). Howver, this is what the vSmart is supposed to do without our intervention. That's why it's so expensive to buy!

Interestingly, our vSmart has never caused the boiler to "modulate" as shown in the video in my first post. It only ever switches the boiler on and off. Once the boiler has fired up, the vSmart never reduces the target temperature. We've never seen anyone else post a comment that the vSmart doesn't modulate the flow temperatures, so we have a nagging concern that there's something wrong somewhere in how something's set up, and we're the only people in the world with this problem. Any thoughts?

Matt, have you been able to solve the problem this autumn? if yes would you be so kind to share it with me since I have the same problem

 

[Nick norman]

I got a Vsmart about a month ago. Initially fairly disappointed for the reasons mentioned here - the flow temperature seemed only to depend on the outside temperature (and the heating curve setting) but not on the difference between actual room temperature and target temperature. Consequently cycling between very hot radiators and cold radiators. Of course reducing the heating curve once things were warmed up helped a lot, but it meant that the house (badly insulated Victorian house) was slow to warm up in the morning. So it was only any good if I reduced the heating curve during the day and remembered to set it back higher on going to bed. Not exactly Smart!

Lots of fiddling ensued, and eventually I phoned the tech line. The advice was to turn off the “heating prediction” setting in the App. That is the setting that varies the time the heating actually comes on, so as to achieve the desired temperature at the time stated. I tried to get out of him how this could affect the flow temperature / load compensation but he was cagey (probably didn’t know!).

Anyway, I tried it and sure enough the system is much better now, with flow temperature varying with the difference between set and actual temperature. It means the prediction thing no longer works but I don’t mind that, it was mostly a gimmick. Although it is a bit annoying that the expensive system doesn’t actually do what it is supposed to!

So in summary, my recommendation for those with too-hot radiators once the house is up to temperature, is to switch off “Heating Prediction” and change the schedule so the heating comes on earlier.

 

[Harry Bloomfield]

Lots of fiddling ensued, and eventually I phoned the tech line. The advice was to turn off the “heating prediction” setting in the App. That is the setting that varies the time the heating actually comes on, so as to achieve the desired temperature at the time stated. I tried to get out of him how this could affect the flow temperature / load compensation but he was cagey (probably didn’t know!).

That is what I too found, when I tried to discus the system with Vaillant tech. My 470 Vsmart is still controlling the temperatures perfectly, within a fraction of a degree, as I have previously suggested, but it is still changing its 'desired temperature' setting. I have its default 'day temp' set to maintain 18C, manually nudging it up to 20C when we are sat around relaxing. To store the 20C as the new 'desired temperature' I should have to press 'OK', which I do not do.

My Vsmart seems to second guess me sometimes and strangely change the 'desired' to 20C. It does similar with the 'Night setback temperature' storing it sometimes as the default, if I happen to stay up beyond the 'night setback time' and tweak the temperature up a little temporarily.

Talking to Vaillant tech, they seem to know little about how it works, they just want to assume a fault and send an engineer out. The manual suggests the outdoor sensor is able to pick up the radio clock signal, to set its time automatically, they didn't even know it doesn't apply to the UK version of the system - the time has to be set manually.

I said it controls the temperature perfectly, the one thing it cannot do is compensate for solar heating, where the winter sun streams in through the windows, or it gets really dark, wet and cold outside. I find myself manually tweaking the set temperature to compensate for that

 

[Pete the Feet]

Speaking from personal experience of outside weather compensated systems in a commercial environment. I always found that Autumnal weather often presented the most challenging in achieving a satisfactory internal temperature in relation to outside temperature. A sunny spring day but cold day could often cause overheating but nobody ever complained about this. However a relatively warm but windy day would bring the complaints flooding in. The solution I used was an anemometer, so if the wind sped exceeded 10mph then it would ramp up the flow temp by 10C. This worked a treat and I could see that wind chill factor could easily be adopted in a VSmart installation if using local weather data and maybe an offset for tweaking.

 

[Harry Bloomfield]

The solution I used was an anemometer, so if the wind sped exceeded 10mph then it would ramp up the flow temp by 10C. This worked a treat and I could see that wind chill factor could easily be adopted in a VSmart installation if using local weather data and maybe an offset for tweaking.

I notice how warm or cold I feel in the house, despite the temperature in the house being very stable, varies quite a lot even sitting about doing nothing very much. I can get up on a morning and be quite comfortable with 18C for several hours, later I might feel chilly and nudge it up to 20C. The weather outside also seems to make a difference to how I feel the chill too, wet and cold outside, I feel it more indoors.

Autumn and spring, I do seem to like it to be a little warmer indoors maybe 22C - perhaps in autumn due to becoming used to the summers heat, then in spring anticipating the summer

No matter what the setting, SWMBO always complaints she is cold

 

[Pete the Feet]

Sometimes the air temperature can read okay but the feel of the room tells you different. This used to be known as the resultant temperature. A simple way to describe it is when you step into a hotel/motel room that feels cold after you have activated the heating with your room card. Although the room air temperature is say 21C it still feels cold. This is due to the fabric of the building being cold.
I suspect inveterate fiddlers such as ourselves will experience this more than most normal folk who are content to just sit back and turn everything up.

 

[Nick norman]

Sometimes the air temperature can read okay but the feel of the room tells you different. This used to be known as the resultant temperature. A simple way to describe it is when you step into a hotel/motel room that feels cold after you have activated the heating with your room card. Although the room air temperature is say 21C it still feels cold. This is due to the fabric of the building being cold.
I suspect inveterate fiddlers such as ourselves will experience this more than most normal folk who are content to just sit back and turn everything up.

Yes I certainly notice that there is a big difference between the room being at 20.0 degrees with the radiators stone cold, vs radiators hot. I think it is that we are quite sensitive to the radiant heat coming from a radiator even if it isn’t that nearby. And as you say, if the walls are cold but the air temperature is warm, the absence of radiated heat from the walls is noticeable.

 

[Teknoline]

hi, I'm from Turkey. VSmart, erelax, migo have software problems on these devices. it will never please you. the heating curve is updated every 15 days (with automatic heating curve and manual curve). if the outside temperature goes beyond the learned outside temperature, it either cannot heat or overheats. you cannot prevent this. I am very glad I bought the vrt50.

 

[Matthew B]

We're in contact with our local Vaillant "Controls Champion". He's suggested various things, including turning off predictive heating (which didn't eliminate the fluctuations in room temperature once the room was up to the setpoint, so eventually we turned it back on), allowing the boiler the full range of flow temperatures (which had the boiler running at 75°C until we got tired of that and limited it to 65°C), and taking the heating curve down to 0.1 (which somehow made the predictive heating decide we only needed 15 minutes to raise the room temperature by 2°C!). We've now got the boiler restricted to a maximum flow temperature of 65°, which should be plenty given that our heating curve has set itself to 0.9, and predictive heating on. Our Champion has said he's going to talk to some people further up the technical tree, so hopefully he'll come back with something helpful. We still can't understand why a vSmart would call for a flow temperature of 93°C when Vaillant's domestic boilers such as ours cannot be set to provide a flow temperature higher than 85°C anyway... And why does a 6 degree difference in outdoor temperature result in a 1 degree difference in the flow temperature requested by the vSmart? It should be much more sensitive than that, surely?

 

[Teknoline]

The room temperature will always fluctuate as long as vsmart adjusts the boiler to the outdoor temperature. It is necessary to cancel the outdoor temperature. The vrt50 provides excellent and stable room temperature. netatmo works super beyond. vsmar is a very bad thermostat