What setting for DHW part load on Vaillant boiler?

[Yikes]

I have an ecoTec 418 boiler with VR65 controller, VRT392f thermostat and a conventional 42x18 HW cylinder.

I have set the CH part load to 12kW and it keeps the house nice and warm. The HW part load is at the default value of 18kW. Is there any advantage to reducing this, i.e will it save money? Here's a graph of how it's all working at the moment. 66% modulation = 12kW.

Thanks,

Mike

 

[ScottishGasMan]

If the boilers heating the water ok and the burners not cycling on and off during hot water reheat then I would leave it as is. Some conventional older cylinders had coils that could only transfer a low power (say 4kW) so when the boiler would heat them it would cycle on and off a lot, which is wasteful and adds stress to the boiler, so in that case I'd range it down until it can heat on a continuous run. But if its already doing it ok then I'd leave as it is.

Out of curiosity what are you using to log the data?

 

[Yikes]

Thank you for explaining that, I shall leave it as it is then.

I built the adapter described here ...

Floris Romeijn – Trust me i'm an engineer

fromeijn.nl

... installed ebusd on a Raspberry Pi ...

GitHub - john30/ebusd: daemon for communication with eBUS heating systems

daemon for communication with eBUS heating systems - GitHub - john30/ebusd: daemon for communication with eBUS heating systems

github.com

... and wrote a python script to capture the data.

Mike

 

[ScottishGasMan]

ahh, nice one, Had my PI monitoring the flow/return temps using external probes for a long time, but could never get my head around the scripts and coding side of things, just kept it simple lol.

 

[Yikes]

Yes I started out the same way but wanted more information. I understand electronics and software far more than I do boilers!

Mike

 

[old duffer]

Data is just noise if it does not provide an answer to a question or can be used to make autonomous decisions....if its manual intervention that is required after looking at something then its not automation..great graph..what's the point?

So I see a boiler being switched on/off yet the room temp remaining constant irrespective of flow temp. That's not right.
What is the time frame and method for collecting room temp data?
Where is the gas consumption data? Don't you need that to calculate operational efficiency as a £ value?

 

[Yikes]

Data is just noise if it does not provide an answer to a question or can be used to make autonomous decisions....if its manual intervention that is required after looking at something then its not automation..great graph..what's the point?

So I see a boiler being switched on/off yet the room temp remaining constant irrespective of flow temp. That's not right.
What is the time frame and method for collecting room temp data?
Where is the gas consumption data? Don't you need that to calculate operational efficiency as a £ value?

I'm a retired electronics engineer. I like data ...

The room temperature is collected from the VRT392f every 10 seconds. Here is an expanded graph of the central heating operation:

The room thermostat is set for 18degC so it seems obvious to me that the boiler will keep supplying heat until that temperature is reached.

Mike

 

[ScottishGasMan]

Looks like it's set to on/off control (two point)

Rather than modulation control (analouge)

Could be worth looking in the room stats installer level and changing it from two point to analogue.

This let's the boiler use lower flow temperatures and condense more, and can reduce the number of ignition and off cycles.

 

[Yikes]

Thanks for that. You're right it was set to two point (default). I have changed it to analogue and will be interested to see what difference it makes.

Mike

 

[old duffer]

I'm a retired electronics engineer. I like data ...

The room temperature is collected from the VRT392f every 10 seconds. Here is an expanded graph of the central heating operation:

View attachment 296699

The room thermostat is set for 18degC so it seems obvious to me that the boiler will keep supplying heat until that temperature is reached.

Mike

I'm also (was invloved, retired now) a multi award wining embedded designer of 20 years plus commercial development with my expertise being in RF network communications so I'm one for keeping data packets simple and meaningful as I an ultra low power kinda guy. ps my boiler interface uses the Ti CC3200.

So in order to raise your room temp by 1 degree, I see that it took 1 hour to do this and I can see that the boiler kicked in/out 6 times, with burn times much longer that pump run times (just circulating the water).
how much gas did you consume doing it this way? What was the outside temp? a staring point of 17 degree is not cold by any stretch...
What can I do with the data? What do you do with it?

I have around 736m3 to heat. Its over 5 levels and I use 15 rads. The boiler is rated 24kw. None of the rads have TRV's, I have no heating zones and no room thermostats.

I have a constant 16 degree room temp @ 50% humidity (in every room in the property) which we find comfortable
I achieve this by using a flow temp of max 35 degrees and the heating runs 24/7.

When its really cold (in the - range outside) I need to take it to 18 degrees (above which it becomes too warm)
I have 2 options of achieving this which is either increase flow temp to 50 degrees for a few hours or set the boiler to take over in auto mode (starts using air intake temp samples every 15 minutes) and compares heat gain in the rooms by measuring return temp. Auto mode I find is best left switched on to work best at times when day temps day by day vary (as we have now)
So having mapped the home, collected the data, I created an understanding of the property and then experimented with controlled intervention to achieve desired outcomes.

The data did its job so I don't need it any more.
ps have you considered running proxmox and puting everything in one place?

 

[Yikes]

Well I'm glad you've got your system working how you want it. I've only just started with mine so it will take a while.

Mike

 

[Yikes]

Looks like it's set to on/off control (two point)

Rather than modulation control (analouge)

Could be worth looking in the room stats installer level and changing it from two point to analogue.

This let's the boiler use lower flow temperatures and condense more, and can reduce the number of ignition and off cycles.

View attachment 296727

I have a comparison between the two modes for the period midnight to 10am. The HW is timed to come on from 5am to 6am and the CH from 6am to 9am. Here is the plot for 2-point control. The heating comes on briefly before 5am when the temperature drops to the set-back of 15C:

Here is the plot for analogue control. Although the overnight temperature stayed above 15C the heating come on throughout the night. I haven't started to measure gas consumption yet but it looks like this mode is prioritising comfort over economy? All that firing can't be good for the boiler.

Mike