Vaillant ecotec plus 832 and VSmart does it look right to you?

[icchis]

Hi all, I have an ecotec plus 832 and less than 2 weeks ago I installed a Vsmart thermostat by myself. The graph under information in the app doesn't look quite right to me and it looks like the boiler turn on/off instead of doing modulation. Am I missing something? Thank you.

 

[Seliaks]

The graphs in the vSMART app are pretty useless, it just gives you the % of time during that time slot that the boiler was fired and providing heat. Your graph does seem to be missing the 'desired temperature' line, but otherwise looks normal. You can pinch/stretch the graph to see more detail for each day (see my graph below - android app). The boiler will be modulating itself as required during those periods. I have requested to the app developers that they add outside temperature to the graphs, and actual kWh gas use of the boiler, but I doubt they will. I think vSMART is a bit of a forgotten lovechild between Vaillant and Netatmo.

I have had vSMART in place for about 5 years so can give you some tips on settings if you need them.

Tom

 

[icchis]

Thank you for your reply. I want just to figure it out why if my VSmart is doing something dumb or it's really smart. I set a temperature of 20* and when it reaches it it looks like the boiler doesn't maintain. The temperature after a while drops to 19.8 or 19.7 and then the boiler fires up again until I can see a 20.2 or 20.3 in the app. I thought it's supposed to reach the set temperature and then modulate to maintain it pretty much constant.

 

[icchis]

I read to set the flow temperature to 75 degrees because I have a VSmart (it was at 60 before). I'm testing it this couple of days to see what happens

 

[Seliaks]

As you can see from my graph, it doesn't really get to temp and hold, it shuttles a bit. It's a compromise, you could set the heat curve lower so that it never quite reaches the set point, and then the boiler will be running all the time, but then it will take a long time from cold to get up to near the set point. If you set the curve higher it will get up to set point quickly and then overshoot and shuttle on and off holding it within 0.2C or so of set point. As the boiler itself cannot modulate below say 6kW, you may find you're using more gas when it's running all the time compared to a more on/off curve. On mine in the 'heating parameters' settings, I currently have the heat curve set at 1.8 using 'hysteresis' algorithm with a threshold of 0.2C. I have tried the 'advanced' algorithm, and find it calls for much higher flow temps from the boiler and overshoots the set point by a bigger margin and uses more gas overall, but the house feels warmer.

 

[icchis]

I've tested the last 2 days with the advanced algorithm and now I'm testing two days with the hysteresis to compare how much gas I use. The temperature outside are pretty much the same over this 4 days. Let's see what I'm gonna find out.

I noticed from your screenshot that there is a flame symbol next to boiler operations. Does it indicate when the boiler is running? I've never seen that icon.

 

[Seliaks]

The flame symbol is there all the time, it doesn't indicate boiler on or anything. Are you on iOS rather than Android?

My experience with the advanced algorithm is it's very erratic, more prone to overshoot. I'll be interested to hear how your comparison goes.

 

[icchis]

I'm on iOS. My test ends tomorrow night. I'll post my results

 

[Seliaks]

My graph for the same time period as yours. I see that the desired temp line disappears when you go to this scale, and you lose detail.

 

[Seliaks]

If you want to check your boiler is modulating, have a look at the LCD display on the boiler when it's fully fired up near the start of a heating period. The flame bar graph will be maybe half way up the scale or higher, and once the system is getting closer to the set temperature the bar graph will be lower as the boiler is ticking over, holding the flow temp steady.

The main thing you'll see with vSMART is the weather compensation effect. When the outside temperature is say 10C, the flow temp it requests from the boiler will be lower than when it's 0C etc. How much lower will depend on what heat curve you're using. The new MyVaillant app (not compatible with vSMART but can use in demo mode) has some useful advice on heat curve settings, and an interactive graph that seems to match with what vSMART requests from the boiler.

 

[icchis]

Seliaks can I ask you which value you used for flow temperature and the value you see on D.9, D.40 and D.41 when the boiler fires up?

 

[Seliaks]

I have the max flow temp at the boiler set to 75C but hope I don't see that much in practice. So today I have vSMART set to advanced algorithm, with a heat curve of 1.4 (if using hysteresis I would use 1.8 to get similar flow temps - not sure why there's a difference) and at D9 I saw that it was asking for 67C (at a setpoint of 18.5C and room temp of 17.5C). The system had been running for about 45 minutes and D40 was at 67C and D41 at 60C - which is a very low temp difference in my untrained opinion, no chance of condensing at that return temp - at best I see 11-12C when the boiler first fires up properly at the start of a heating period. Having put some temperature clamps on the flow and return pipes, I think the return sensor reads about 10-15C too high, but it's difficult to be sure. When I check the temp difference across the radiators they all feel about 15C difference - the temp clamps kind of confirm this, but they need a really good contact to get a decent reading, which is difficult to achieve.

I did an experiment this morning to see if vSMART implements any form of load/room compensation - I put the thermostat unit outside - it only checks the room temp every two minutes, and the unit is quite slow to react, but after a while it was showing a room temp (outside) of 13.5C - so 5C below setpoint. I did this with the boiler switched off, so when it restarted, I checked and D9 was again showing 67C, so, as far as I can tell, vSMART only uses weather compensation, with no factoring in of the difference between the room temp and the set point.

 

[icchis]

I have a very similar situation and basically the same flow and return temperatures. My curve is set automatically by VSmart to 2.2.

As far as I know the VSmart calculate how much heat is needed to reach the target temperature based on the outside one.

 

[Seliaks]

In my experience it doesn't do a very good job of calculating the heat curve. If I allow it to auto-select it always goes to 2.6, and calls for crazy flow temps. I think there's something wrong with the maths that controls it - using a heat curve of say 1.8 it asks for different flow temps depending on whether you're using advanced or hysteresis algorithm, which doesn't seem right. I think the best option is to set the heat curve yourself -if you set it too low the room will never reach the set point, if you set it too high it will heat up quickly but probably overshoot a bit, and then shuttle on and off over the day. Having looked elsewhere on this forum, it looks like the Vaillant controls with load/room compensation do a better job of holding the room temp steady and appear to allow the boiler to modulate better. I'd have a play with the heat curve if you're not happy with how it's behaving. What was the result of your monitoring of the gas use?

My boiler (Ecotec Plus 624 system boiler) seems quite tolerant of a low difference between the flow and return temps, and can run for hours with just 4C difference - if they get too close it is designed to shut down and anti-cycle (egg timer symbol) until it's cooled down a bit, and then start up again. Once the system reaches your set point on the vSMART the boiler will also shut down and show the egg timer symbol, which is fine, but if it does this before you've got to the required room temp it will take a long time to get to temp - if that is the case it may be that your pump speed is set too high, or the bypass valve set too low - the pump speed can easily be changed in the diagnostics menu, the bypass valve probably needs a suitably trained person to adjust it. If I set my pump speed to 'Auto' the next d code says that the pump is running at 15%, but if I switch the pump to 53% the sound from it doesn't change, so I don't believe the 15% is correct - I think it can't run any slower than 53%.

 

[icchis]

At the moment I put my heat curve to 2 and I don't have issue to reach the target room temperature and it's able to maintain it with some variation of +0.4 / -0.2 (the threshold is at 0.2). Tonight my test ends and I'll see if I spent much gas with the advanced algorithm or the hysteresis one.