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

When I tried that I found the house wasn't as warm as it could be, and it's probably an experiment best carried put when the weather is cold? As for my earlier comment about not being able to read flowtempdesired on the bus, I meant via MQTT, so for example this works: pi@vaillant:~ $ ebusctl read -c bai flowtempdesired 10.00 pi@vaillant:~ $ ebusctl read -c bai FlowTempDesired 10.00 pi@vaillant:~ $ ebusctl read -c bai FlowTempDesired temp 10.00 And these work: pi@vaillant:~ $ ebusctl read -c bai ModulationTempDesired 63.0 pi@vaillant:~ $ mosquitto_sub -t ebusd/bai/ModulationTempDesired/# 63.0 But this doesn't: mosquitto_sub -t ebusd/bai/FlowTempDesired/# Mike

On a positive note and thanks to Radian's help earlier I can now monitor my boiler from my phone with a free MQTT app. Mike

Yes agreed, but I'm pushed for time as the weather is getting warmer which makes it harder to get a meaningful result. As for disablehc, with the thermostat in 2-point mode it appears to act as a conventional on/off switch whereas in analogue mode it follows the CH programme (6am to 9am). HW is 5am to 6am. On the subject of flowtempdesired it's one of the few parameters I am unable to read on the bus. Don't know why ... You might just be able to see evidence of micro-firing in the above plot, which was logged at 30 second intervals. Zooming in for the rest of that day to 10 second intervals shows it more clearly. Also the Room temperature is well above target: I read elsewhere that micro-firing with the VRT392f thermostat can be eliminated by changing to return regulation, so that was today's experiment. Almost no micro-firing but back to short cycling and the modulation is stubbornly stuck at 63% ... Mike

OK the rabbit hole just got deeper ... I changed the room thermostat mode to Analogue and set the CH Part Load to 6kW which is what I estimated the property's heat loss to be. There is also a +/-5 Distance setting which affects the response time to compensate for the distance between thermostat and heat source but I left that at zero for now. The obvious differences over 2-point mode are the behaviour of flowtempdesired and disablehc. The weather is now too warm for a proper evaluation but I would say this is looking promising. What does the panel think? Should I increase the CH Part Load? Mike

Yes that works! Thank you Sir 😀. Mike

I still need some help on this please. I have made the changes above but I'm not sure what commands to send. Do I do this: mosquitto_sub -t ebusd/%circuit/%name/%field Or this: mosquitto_sub -t ebusd/bai/FlowTemp/temp Then what do I send to read the bus? Mike

My boiler is a 418 (my friend has the 428) but yes 5kW is the minimum and yes I am logging modulation 😀. It gets down to 33.3% which is 5kW. Mike

OK so with my room thermostat in conventional 2-point operation the modus operandi is for the boiler to run until room temperature is reached then revert to short cycling. I have a friend with an ecoTec 428 and conventional thermostat and his behaves the same so I guess that is normal operation. I will try the room thermostat in analogue mode next. Mike

Thank you. I will give that a go once I've got the boiler's behaviour sorted. Mike

Sure, here it is: version: ebusd 23.1.23.1 update check: OK device: /dev/ttyUSB0 access: * signal: acquired symbol rate: 39 max symbol rate: 146 min arbitration micros: 302 max arbitration micros: 6435 min symbol latency: 0 max symbol latency: 16 reconnects: 0 masters: 3 messages: 371 conditional: 3 poll: 0 update: 11 address 03: master #11 address 08: slave #11, scanned "MF=Vaillant;ID=BAI00;SW=0518;HW=7401", loaded "v aillant/bai.308523.inc" ([HW=7401]), "vaillant/08.bai.csv" address 10: master #2 address 15: slave #2, scanned "MF=Vaillant;ID=F3900;SW=0120;HW=2102", loaded "va illant/15.f39.csv" address 31: master #8, ebusd address 36: slave #8, ebusd address 64: slave, scanned "MF=Vaillant;ID=V6500;SW=0007;HW=8301", loaded "vaill ant/64.v65.csv"