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Well having torn my hair out, and having created a large head-shaped dent on the front of my Vaillant boiler (lol jk ;0) I have made some progress here, which might in fact answer my own question. This is maybe not the end of the story, but at least if others are looking for answers they might find help here. A lot of reference was made by chatGPT to a parameter SetModeOverride which can be sent to the Vaillant to override the boiler's internal controls, but this wasn't appearing in the list of available parameters on an Anyhow, I found reference to adding the correct settings to bai.308523.inc as follows:
So I did this, and with the following parameters I can now update the boiler flow temp programatically to e.g. 55 degrees!
So I think my current issue is resolved, unless anyone has a different/better way to do this. I wonder why the line is missing from the config file though (in both the German and English versions). @john30 I wonder if you could check my work here and let me know if I've missed anything more obvious? It might be worth putting this in a useful place of examples as I can't imagine I'm the first to want to do this. Many thanks |
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I discovered that the SetModeOverride command needs to be manually added to your configuration files. Specifically, in the file bai.308523.inc, I added the following line: r;wi,,SetModeOverride,Betriebsart,,08,B510,00,hcmode,,UCH,,,,flowtempdesired,,D1C,,,,hwctempdesired,,D1C,,,,hwcflowtempdesired,,UCH,,,,setmode1,,UCH,,,,disablehc,,BI0,,,,disablehwctapping,,BI1,,,,disablehwcload,,BI2,,,,setmode2,,UCH,,,,remoteControlHcPump,,BI0,,,,releaseBackup,,BI1,,,,releaseCooling,,BI2 ebusctl write SetModeOverride '0;55;0;-;-;0;0;0;-;0;0;0' |
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yup! It took me days of googling/chatgpt to find this missing piece of the puzzle! It works perfectly via mqtt as well: . @john30 are there any 'gotchas' we need to be aware of when using this? Here's my automation for setting the boiler temperature in Home Assistant: I hope this is helpful to anyone else who wants to do this. |
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Hi Tim, looks like you've solved your problem by the time I saw your original post! From the readings I did on the forum a while back, I think SetModeOverride was a community member(s) initiative to effectively created a writable clone of SetMode. I think there might be some understandable reluctance to PR it into the official files because in the 'wrong hands' it could be a little dangerous. But sounds like if you're implementing PDHW you know what you are doing! (out of interest why did you go W Plan in favour of X Plan - was it you were converting from Y rather than S? Also do you control your own weather comp in HA with your own heat curve or rely on the boiler's algorithm for that and simply override flowtemp for DHW?) Gareth |
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Hi Gareth - thanks for your reply! I've used X plan as I was converting to PDHW from an existing Y-plan. Basically to test how it behaved. My plan is to use HA to implement a sensible heat curve for the house. Just need some cold weather now. However, I've been struggling a bit with getting sensible heat out of the system. i've installed a heat meter in the boiler circuit to measure real power from the boiler which is yielding some interesting results. Basically I can't seem to get more than around 650 litres/hour through the pipework. I suspect this this is in turn limiting the power. I also can't get a DeltaT of more than about 11-12 degrees. ChatGPT tells me with this flow and deltaT I won't get more than about 8.4 kW out of the boiler. Wonder if there's somewhere else to look to change this? As part of my investigation into flowrates, I've closed down all rads, and opened them up 1 by 1 and I get from 138 to 420 litres per hour though each radiator in turn (depending on pipework to each rad, etc). If I add up the flow rates I get 4590 litres per hour, so with the pump running I'd expect a fair bit more than 650 litres per hour. So I'm beginning to wonder if the pump itself is not performing well. Or the inbuilt bypass is bypassing too much? This is probably not the forum to discuss the details of my HA/Vaillant CH woes though! Cheers |
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Hi Tim, I can see you've dived down the same rabbit hole I did a couple of years ago. I had the good fortune (?) to design my system from scratch as the house previously had storage heaters and I drew the line when the lecky bill hit £1K a month for the cold months! I couldn't find an installer who was willing to invest the time in a room by room heat loss analysis - so I did it myself - and supersized rads so I could get to 'near heat-pump' flow temps and dT, having been told a HP was impossible in my thatched one-room wide property. I think I've ended very close with an LPG boiler - my flow is rarely over 55 and mostly lower using weather comp and my dT is also not much more than 10. (Controversially replaced an unvented cylinder (albeit direct) with a Combi rather than System -and still not sure how I feel about that!) This was a few years ago so have mostly forgotten all the science I ingested (an age thing) - if you don't have CIBSE's Domestic Heating Design Guide - then I commend it to you - especially chapter 5 on systems design - this covers flow rate, pipe and emitter sizing and pump sizing etc. My lingering regret from the install was I felt the installer skipped on pipe diameter (mostly MLCP due to nature of the property, copper on surface) and that as a result my water velocity is too high - although I don't experience noise - but I also have a really low dT - as if the emitters don't have an opportunity to consume the heat. Ultimately, thought the house is warm when I need it so it's about tinkering.. (and even LPG - so much cheaper than electricity!) A few random thoughts: If you are determining dT from d.40 and d.41 - I've found these sensors to be .. meh. Perhaps because they are too close to each other in the boiler. I've installed little ESP32s with DS18b20s on the actual pipes reporting to HA and I trust these more. What does d.29 show? This is flow rate in l/s on the panel (and some weird unit from ebusd - I've not quite got the bottom of this but maybe needs multiplying by 64 - fwiw my boiler loads bai.308533.inc - YMMV) 
As I say, probably forgotten all I know, but maybe Chat is getting it the wrong way around? Essentially you've got emitters - rads - which are like load in an electrical circuit - they determine what heat gets emitted in the room (well also some additional extra through any exposed pipework). Your pipework - determined by diameter, material (copper, pex etc.), and mass flow rate determine whether that power can be delivered - much like the diameter of electrical cabling - twin and earth etc. From what I recall (do not trust!)- it's not additive - in the sense that you need to work out your 'index circuit' to see whether the pump has enough 'head'/pressure to power the system. In other words, if the pump can serve the 'hardest route' it can satisfy the other routes. So unless you have a perfectly circular flow return design with no T's, you will have an index circuit. Most pumps in (relatively modern) boilers are super-capable of delivering the required head/pressure - I suspect your 624 isn't that old, so wouldn't necessarily blame the pump unless you also have an external pump - which could be whole other world of pain? Do you know how many kWh you need - is it more than 8KWh? They reckon the 'average' UK house in the housing stock needs not more than 6-7. (although I calc'ed mine at 16 so it's not unusual to have exceptions!) Agree - we've probably gone super off-topic for ebusd, although I'd argue this amazing tool is the only way these types of discussions are enabled! I'm just down the A303 from you at Nether Wallop, and my wife says she is going to turn the heating back on soon with the current weather so maybe will start to get real data again! Happy to continue the discussion though - forums like diynot.com might be a place where you'll get some non- EBUSD specific assistance? What heat meter did you install? I toyed with that too - so interested in what you went with. Cheers, Gareth |
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Hi Gareth
Thanks for your comments!
If you are determining dT from d.40 and d.41 - I've found these sensors to be .. meh. Perhaps because they are toclose to each other in the boiler. I've installed little ESP32s with DS18b20s on the actual pipes reporting to HA and I trust these more.
I’ve got some dallas sensors with esp32 strapped to the flow and return. Values are within a degree or so of the Vaillant.
What does d.29 show? This is flow rate in l/s on the panel (and some weird unit from ebusd - I've not quite got the bottom of this but maybe needs dividing by 64 - fwiw my boiler loads bai.308533.inc - YMMV)
This parameter isn’t available on my boiler. It’s 2012 vintage so predates the flow sensor?
From what I recall (do not trust!)- it's not additive - in the sense that you need to work out your 'index circuit' to see whether the pump has enough 'head' to power the system.
Aah yes. I need to dig into the Index Circuit and balance things from there. More work needed! I Think my index cct is the kitchen patio radiator, coming in at 2.something l/min.
Most pumps in boilers are super-capable of delivering the required head/pressure - I suspect your 624 isn't that old, so wouldn't necessarily blame the pump unless you also have an external pump - which could be whole other world of pain?
It’s the Vaillant internal pump. I’m wondering if it’s lost some of its ‘oomph’ ? No idea how to tell though. I’ve twiddled it and it runs freely.
Agree - we've probably gone super off-topic for ebusd, although I'd argue this amazing tool is the only way these types of discussions are enabled! I'm just down the A303 from you at Nether Wallop, and my wife says she is going to turn the heating back on some maybe will start to get real data again!
Very close to us. I’ve got customers in Broughton, Houghton and Stockbridge so travelled past regularly. Less so now I’m retiring though. More time for boilers!
Happy to continue the discussion though - forums like diynot.com might be a place where you'll get some non- EBUSD specific assistance?
Perhaps we can continue on your github discussion forum?
What heat meter did you install? I toyed with that too - so interested in what you went with.
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Yes, sure! Gareth |
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Hi Gareth
I think I might possibly have hit ‘send’ too early!
I’ve got a Kamstrup 603 heat meter with the 230v supply and Modbus option. I’ve got it talking to Home Assistant really well and I’m able to also read the smart gas meter into Home Assistant. This gives me a great way of looking at efficiency by comparing input kWh with output kWh. I’m getting around 87% efficiency with heating DHW tank. Not as high as I was expecting. See the graphs attached for interest.
What heat meter did you install? I toyed with that too - so interested in what you went with.
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So I've spent a couple of days trying to get my head around how to do this seemingly simple thing!
My heating control is already under Home Assistant, and I want to enable the hot water tank to charge with a flow temp of approx 60 to 65 C, but vary the radiator flow temp based on outside temperature. I've already got PDHW (W-plan) configured, so I know when the boiler is providing heat to radiators vs hot water.
I can read all of the things via MQTT in Home Assistant, so the general connectivity between HA and my boiler is a-ok. What I want to be able to do is to set the parameter DesiredFlowTemp, without me having to twiddle the Heating temp knob on the boiler as the outside temperature changes!
bai FlowTempDesired = 60.00Here is the output of ebusctl info:
and the output of find -a:
I've gone through many posts trying to understand how to get my boiler to accept my command to programatically change the flow temp but have failed! Has anyone else managed to get this working? I understand the trick is to convince the ecotec that it's got an external controller connected to the ebus, and to send keepalive messages which will enable me to write to parameters that are currently read-only. ChatGPT has given me various false leads! Am I barking up the right tree? If so what is the process I need to follow?
Many thanks!
Tim Robinson
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