Optimization / base point not respected and unwanted burner starts

[moritzthecat]

Thanx to ems-esp we now have more insight into the parameters of our heating setup.

We have a Bosch Junkers CSW 14/75-3 A (HT3 type) boiler with low loss header, MM100 mixer driving the floor heating. In ems-esp this is setup is reported as Condens, Logamax/Logomatic, Cerapur Top, Greenstar, Generic HT3 (Boiler). Thermostat is CW 400 (RC310).

From logging there are some observations, which I do not understand how to optimize further.

Could you pls. indicate if and where to post a discussion about further optimization. Is this Github general discussion a good place ?

I would expect that users of esp-ems are best suited for such discussion being both more familar with EMS type of control and interested in optimization of their heating sharing advice.

Appreciate also to know any related tutorials, which might be useful?

[proddy]

This is the right space. You could do a post on Discord pointing to this - that may attract some more attention.

[moritzthecat]

Heating setup as described above #2324 (comment)

Floor heating has all valves opened (hydraulic adjusted setup) and thermostat is installed in the living room to drive room influence. In normal operation room influence is minimal and mainly affectd by sun or our wood oven heating up the buildung.
House type is set to medium (hollow blocks). Energy consumption last year (2024) including warm water was 56kWh/m2.

HC1 (boiler)

• control mode: outside basepoimt
• Heating curve -20C (lowest possible values otherwise rooms getting too warm) and design temp 34C (a bit higher than hc2)
• Hysteresis -4K
• Max Power 55%
• Base point/min flow 24C

Hc2 (floor heating) curve
control mode: outside basepoimt + room influence

• Heating curve -20C (lowest possible values otherwise rooms getting too warm) and design temp 32C
• Manual mode and no setback configured.
• Room influence 2°C to limit impact by oven for other rooms.
• Room influence factor = 1 (not sure what this means – have not seen effect with higher values)
• Mixer increase = 0K (not in ems-esp but thought is important)
• No fast heating configured

Use case for this discussion: remain floor temp at 24C (base point) even if oven is used and room influence is reducing flow target.

1. Why are there burner starts between 22:00 and 05:20 while mixer is at 0% ? These burner starts cannot contribute to increase floor temperature. I would expect that flow temp follows exactly the target flow setting. How to avoid such useless burner starts?
2. Around 02:00 flow temp falls below flow target. Why is mixer not opening and triggering a burner start to maintain 24C base point?

Screenshots from Grafana Dashboard

[oliof]

Here are some comments about what's happening, compared to my Buderus GB172-14 -- probably similar, even though I have only a single heating circuit. I also see the same peaks even though the flow temp is within the hysteresis:

I had set my minimum burn time to 30 minutes at the time of the screen shot, yours look like every 40 minutes?

All in all I can say that the boiler logic seems to fare badly with flow temperatures below 29/30C where I see unexpected cycling and hysteresis, the boiler logic only seems to stabilize at 30C or so.

Regarding your room thermostat: In my testing the room influence factor multiplies the temp adjustment from the room influence setting. I.e. if the room is 0.5C below target temp and you have a room influence factor of 2, the flow temp gets shifted as if the temp is 1C below.

Also, in the discord, @MichaelDvP provided the following recommendations for choosing a room for room influence:

I think there is no usual value [for room influence factor]. If you are heating mainly one room and others are lower by TRV, choose roomcontrol or big room influence. If you are heating many rooms in one hc and they all should be warm, use weather control or low influence. The reference room should always be the one with most heating demand. Also large windows in south direction influence and the north rooms will stay too cold. Just try what room and that influece is good. In logs check flowtemp and roomtemp in the morning whhen switching from night to day mode. With low room influence flowtemp is just set according to outdoortemp and roomtemp is very log increasing. With room influence flowtemp ist much higher until the room reaches it's setpoint, after it's nearly the same. So the room heats up faster and you can adapt the switchtimes.

My heating setup is 'normally open' (all thermostats fully open) with room influence from the bathroom. This already has improved performance of the system a lot because it takes longer / higher outside temperatures to get into low load situations.

I am currently testing SAT to see if its helping with low load situations (target flow temperature below 30C). SAT bypasses Buderus' room influence and you can use whatever temp sensor you want for outside temperature which may or may not be useful for your setup. It also allows multiple room thermostats to keep flow temp up in case the main room is at temp but the others are not.

It may also be worthwhile to experiment with combined room temp sensors and a virtual remote thermostat to get an averaged room influence from multiple rooms.

[moritzthecat]

@oliof thanx for your feedback.

I had set my minimum burn time to 30 minutes at the time of the screen shot, yours look like every 40 minutes?

this parameter (burner min period) was not set yet. trying to change I cannot get values higher than 15min accepted by the boiler. Are there other dependencies ? Does this value limit burner starts between defined period?

All in all I can say that the boiler logic seems to fare badly with flow temperatures below 29/30C where I see unexpected cycling and hysteresis, the boiler logic only seems to stabilize at 30C or so.

yes, definetely. this is reason to look for experience with similar setup and hopefully some good hints.

Regarding your room thermostat: In my testing the room influence factor multiplies the temp adjustment from the room influence setting. I.e. if the room is 0.5C below target temp and you have a room influence factor of 2, the flow temp gets shifted as if the temp is 1C below.

this is understood and flow target is calculated OK as I can see in my example with oven turned on. But this flow target and flow deviation is not respected by the mixer in my case. We are wasting energy by the repeated burner starts with mixer turned down (short circuit). This is not neglectable.

My heating setup is 'normally open' (all thermostats fully open) with room influence from the bathroom. This already has improved performance of the system a lot because it takes longer / higher outside temperatures to get into low load situations.

same here as mentioned above. All rooms are quite same temperature.

I am currently testing SAT to see if its helping with low load situations (target flow temperature below 30C). SAT bypasses Buderus' room influence and you can use whatever temp sensor you want for outside temperature which may or may not be useful for your setup. It also allows multiple room thermostats to keep flow temp up in case the main room is at temp but the others are not.

this is very interesting. could you pls. share some insights and experience with your EMS based heating once available ...

It may also be worthwhile to experiment with combined room temp sensors and a virtual remote thermostat to get an averaged room influence from multiple rooms.

once I have a better understanding of the control and limitations this might be interesing too, since I have 1-wire room temperature sensors in all rooms.

overall the documentation of control is not sufficient to me. I think there is a missing link between supplier manuals and the parameters which could be altered in ems-esp: what is the purpose, value ranges, impact on other parameters and dependencies. To my knowledge this does not exist and could be a nice adddition to ems-esp.

[tp1de]

Let me share my findings/solution:

I was not happy with the number of boilerstarts on medium/low load.
I introduced a "heatdemand" function within my ioBroker adapter.

Having installed smart thermostats in most rooms, I compare actualtemp with settemp.
Each room has a weighting factor and a hysteresis and is linked to a heating circuit.

Each heating circuit sums up the factors where actualtemp < settemp.
If this sum is higher then defined for switching on, then the hc is active otherwise not.

I am using this logic now for 3 years and other users as well. For me it works fine.

Since I moved to homeassistant in the meantime I implemented this version into node-red (ha addon).
If anybody wants to test: https://github.com/tp1de/home-assistant-node-red-heatdemand

[moritzthecat]

@tp1de thanx for sharing.
this sounds similar approach compared with SAT as suggested by @oliof.
still do not understand how to bypass the CW400? - but will 1st read through everything. Weather currently is ideal for such tests...

One remark: Having the supplier recommended setup installed with heat loss header, mixer and CW400 in lead room I would not have expected such issues any more. Also we observe that rooms foor temperatures are getting too cold sometimes and min flow temp setting is not effective - why? Not really any change in comfort to before without mixer and without heat loss header.

I was hoping though that I had overlooked something and could have improved by tweaking using ems-esp . Anyway I will now look into these options. Esp. looking for improvements when we have other room influence by e.g. short time opening windows to get fresh air in or operating our oven longer times the control get´s wild. Thanx again to ems-esp that it is now easier to get access to the needed datapoints and becoming aware of the issues.