I have a question about getting the optimal SCOP out of my heating curcuit on my newly installer Vaillant AeroTherm Plus 7kW ASHP.
The house has underfloor floor heating throughout the building in a 100mm concrete slab with pipes at 150mm centres
The design flow rate is 35(40)C with a dT 5C
The outside design temperature is -12*C
Longest UFH loop requires a flow of 1.1 l/m
The house is super insulated (floors 300mm and loft 300mm and extension with 200mm cavity wall insulation) apart from the old cavity walls which only have 75mm Rockwool insulation.
I have a few questions with regards to optimising my SCOP by setting the best settings in the Vaillant vr720f or VWZ AI controller.
Running with weather compression how do people deal with the autumn and spring where you can see major swings in temperatures. (Eg: Nighttime temperatures at 7C and daytime temperatures at 21C)
What settings make the most sense in my scenario?
Settings > Installer Level > Installation Configuration > Circuit 1
OT switch-off threashold: 17*C
Min. Target flow temperature: 21*C ???
Max. Target flow temperature: 35*C (Is this the flow design temperature or should it be set higher?)
Set-back mode: Eco (Perhaps not relevant using a heat curve if the heating is always on???)
Room temp. Mod: Expanded (or Active or Inactive)
Also do you tend to leave it on manual and just ensure the flow valves on the manifold are set correctly or do you use a timed schedule?
Where do I set the dT for the heat curve?
Right now I have configured a heat curve of 0.3 which looks to me to be about right from the Vaillant manual and the article written on @Zarch blog.
I hope someone can share some of their experience so I don’t have to start from scratch.
I have OT at 14C, but my house loses more heat and can drop internal temp enough to warrant coming back on.
I think i’ve got min at 20C and max at 40C, but check what the min at max curve of 0.3 are. These values here will hamper and override the curve. So better to put these well below and well above the curve values. It looks like you might want to put the max up higher if you want to cover right down to -12?
Set back needs to be Normal for proper setback operation (ie, it uses the setback temp you’ve chosen). In my case 20C in the day, 19C in setback. Eco just doesn’t seem to work.
Personally I use room temp mod Active, just to give a little bit of room influence.
Inactive is pure weather comp. Expanded works like an on/off controller.
You don’t. You just let the Arotherm sort that out. What you’ll see is that when running in mild temps it will be DT2 to DT3. It’s only when you’re getting towards full load that you’ll see DT4 to DT5.
This is because the Vaillant fixes the flow rate and uses the DT to modulate the output.
DT x SHC (4.2) x flow rate = output.
If flow rate and SHC are fixed then it has to use the DT to modulate the output.
That makes sense… I appritiate the reply… Yes -12 is bl**dy cold…
Do you use setback temperatures or have you got flow regularors setup so the heat pump runs constantly??? I can Understand from watching Heat Geek on YouTube that using setback temperatures with ASHP’s is not that beneficial???
I’m not sure which video you saw, but Heat Geek absolutely recommend the use of setbacks.
I’ve detailed my scheduling in the following article that might be useful.
Basically, just use a setback temp that is a 1 or 2 degrees below your main target temp.
ie, overnight or when out of the house in the day.
This means the heat pump continues to feed the house and fabric heat so that when it comes back off setback to main target temp it doesn’t have to work as hard as if you had switched it off completely.
