Does anyone know if Vaillant onboard monitoring subtracts the defrost heat taken from the system in the delivered heat or not?
Hello all, does anyone know if the 3.5kW Arotherm+ has the same compressor as a larger 5kW model? All the info on the datasheet I found is identical for the two units.
If they are the same is there any advantage to getting the 3.5kW model over the 5kW model? The main disadvantage I can see with having the smaller one is DHW heat up time.
They’re the same unit, with the 3.5kW being software-limited. Get the 5kW.
Don’t the 3,5 unit have a smaller heat exchanger then the 5 ? The only difference
When I looked they had the same minimal output thats enough to convince me the 5kw is nearly aways the better option.
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Just got a question about defrost cycles on our AroTherms. Just a quick question and something I’m trying to get my head around. Is there a way to reduce these? I am aware that humidity outside and temperature outside makes a difference but is there any other way to reduce the amount of cycles? What about reducing the heat curve or increasing it?
I am finding when these cycles happen that it prevents the room getting to temp as there isn’t long enough between cycles to get consistent heat into the room/house, I suspect this is just a radiator balancing thing which I am in process of tweaking.
You can see the amount of cycles happening on my system today, I know it’s normal but wondering if I can change any settings
https://emoncms.org/app/view?name=MyHeatpump&readkey=8f21605274780a0df694c37d97b64bd1
You’re not the only one with these issues. In damp, cold conditions the actual delivered heat can be 20% below the datasheet specs because of defrosts. Have a look here or here for some more in-depth discussions on this.
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If you can make it work less hard it may defrost less. Setting the weather curve as low as possible consistent with heating the house (heat pump running 24x7, external thermostats and trvs set to max) is anyway, in most circumstances, the most efficient operating point. Thats also when its working least hard.
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I’ll check them out cheers Andre, I’m on my learning journey with my ASHP, only had it for 4 weeks. I suspect radiators balancing a bit more will help for more comfort in the living room but I am wondering if to have a play with the heat curve more.
Currently at 0.75, desired at 18 during day and from 2130-0700 is 17.5. Would heat lowering heat curve work better and reduce the defrosts?
I suppose that makes sense, our heat curve is 0.75 but I do feel I should lower that a bit more maybe?
I do feel once I got a couple of the more problematic radiators more balanced for more comfort then I feel more confident in lowering the heat curve.
Out system is open loop, TRV open fully, 1 zone. Desired 18 degrees 0700-2130, 2130-0700 17.5
Is room influence disabled. I found i coukd turn my wc down a couple of notches once i did this, and the house temperature was more stable as a result. The great thing about the Vaillant controller is that, even if you disable room influence, setback is still respected - it just shifts the wc curve. Few others seem to do this.
I’m running it in inactive at moment, I assume that mode is room influence off?
Your set point temp is very low, and your heat curve is very high.
Are you actually targeting 18C on purpose? What kind of actual achieved temperatures are you seeing around the house?
Yes, it’s the temperature we thought would be most comfortable for us as that’s what we used for when we had a combi. Should we be going higher on the temp and lower of the HC?
Is it problematic or wrong to run it with low desired and higher HC?
Sorry missed you other bit, all upstairs is around 18.5-19.5 so it’s over shooting upstairs slightly. Downstairs in living room is generally anywhere from 17.2-18 but I’m suspecting that’s radiators not quite balanced so they need tweaking. The kitchen diner I need to check temp as not done that yet.
When in setback seeing around 17-17.5 in living room but upstairs stays around 18 overnight
The HC is set correctly if you hit the 18°C target at all outdoor temperatures. If your house gets colder as outside temperatures drop, you need to increase HC, if it’s the other way round decrease it.
Having that slight discrepancy between up- and downstairs is normal and a radiator balance can fix it.
Are you and other occupants comfortable at those temps? My family would be fuming if anywhere in the house was anything lower than 20C!
If your current achieved temps work well for you, then you can mitigate the effects of defrost temp loss by playing with the heat curve/set point values.
Increasing the curve value and decreasing set point will steepen the curve, raising the flow temp targets when it’s colder… and vice versa.
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I’m asking myself the same thing every day I’m on here reading what temperatures people have in their houses 
. I think my wife might kill me if I set the house to 18°C, then again she’d be frozen solid 
.
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I was told there’s nothing I can do to stop upstairs being hotter than downstairs and “heat rises”, I’d love to understand how turning the lockshield on our master bedroom slightly would impact the system
You certainly can do something about it, my upstairs is colder than downstairs on purpose (bedroom). I have less flow to the rads there and also run the fans below them at lower speeds/sometimes off which does the trick overall. Unfortunately I have no experience with the lockshields, my rads all are connected to a central manifold. But if you restrict flow to your bedroom and observe for a couple of days you can always return to the previous state if everything is well documented. As much as I would have liked doing any math on my balancing, it was all purely experimental in the end.
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