PiMike

I'm experimenting With flow temp. 55C was a starting point. DHW has its own max flow temp and power rating (d.77 from memory) which I left at 18kW. The burner always fires at 63% at the start of CH demand regardless of the d.0 setting. Mike

I can reduce the boiler output with the d.0 setting. 12kW is clearly too much for CH at this time of year. Mike

There's only one TRV in use and it's in a bedroom so on low. I think I need to reduce d.0 a bit. The pump is on speed 2 so I could play with that, or even try the proportional settings. So many variables ... Mike

Ah, I see that now. Thank you John! Mike

My ecoTEC plus 418 was installed in 2009 and I have recently started monitoring the ebus (mainly as a retirement hobby ...). It seems to be behaving strangely and I'd appreciate an educated opinion on this please. When CH demand starts, the boiler fires at 66% (d.0 = 12kW). When Flow Temp Desired is reached (55C) the burner modulates down to 28% (the boiler minimum of 5kW). So far so good, but the flow temperature then immediately starts to rise and when it reaches 57C (exactly) the burner cuts out. 18 minutes later it fires up again and the cycle repeats. Is this normal? Mike

Fair enough, but full power would be 100% not 66% ... Mike

I don't use social media, life is so busy I can't find the time. I'm more than happy with the fantastic help available on forums like this. When my boiler was installed in 2009 I didn't know enough to ask what rating it was. I assumed the installer knew what he was doing ... This puzzles me. I set the CH part load to 8kW, assuming that this is the maximum the boiler would use, but in the graph above it's running at nearer 12kW (66%) at the start of the CH programme. Mike

I read the article, it's very informative. Then I went back to a plot I made earlier this month when the weather was colder and realised it follows their logic. This is with the room thermostat in conventional (on/off) mode. The boiler starts up at 100% modulation (18kW) for hot water then 66% for the start of the CH long burn. Once the flow temperature reaches the target of 65C the modulation drops to 30% but because my boiler can't go below 5kW it starts the short cycles as the room temperature approaches the target of 18C. Mike

Thank you! That will do what I need. 10s is perfect. Mike 😀👍

OK thanks. Can you advise on how to edit the boiler file to achieve this please? I just want a continuous monitor of parameters on my phone without sending commands. Mike

I've tried all possible variations of the syntax and none worked. Now just to spite me the ones that previously worked don't either. ☹️ Mike

Thanks that's useful. Here's a link to the ebus adapter I built: https://fromeijn.nl/ And here's the blog that discusses Vaillant micro firing with weather compensation: http://vaillantcyclingproblem.blogspot.com/p/problem.html?m=1 Mike

Hi Joey, thanks for your input. There are so many parameters to play with! I have a 3 speed pump which is currently on 2 and seems to work OK there. As for weather compensation, I have only just fitted my current Vaillant room thermostat and need to understand it before moving on. There is a blog somewhere on problems with Vaillant weather controls causing micro-firing. I'll post a link when I find it. My adapter follows the ebuzzz design. I bought the PCB and components from China and built it up myself. It cost £20 and works perfectly with my Raspberry Pi. I wrote a python script to capture the data every 10 seconds. That was the easy part for me. Understanding how the boiler is supposed to work is a different matter! Mike

OK I think I'm going to drop the boiler tweaking for now as it's raising more questions than I can answer at the moment. Here are two plots from consecutive mornings, one with the thermostat in conventional (2-point) mode and the other in analogue mode (and return regulation). I can't see too much difference between them. The modulation is 100% (18kW) for HW. For CH the 2-point control looks to be better behaved. Thanks for all the input! Mike

Dropping the /# doesn't help. Leaving out the %field doesn't help either and stops the MQTT client on my phone receiving updates. Mike