jamesdiyer

Noise reduction at 60% doesn't help. So clearly the compression isn't ramping on at that higher rate (power input in still the same as it was without noise reduction around 1600W). I guess this means it's doing a good job of not starting too hard, but I feel it could do better if it started lower % of compressor speed max or modulate down faster.

Yes, I feel it's running in that way, and because we have a 15kW beast, at mild temps circa 10C it heats it really quick. But for example, it's 10C out side right now. But with a huge north wind blowing and snowing 500m above the house. So when it cycles off you can note that it's off. Perhaps increasing radiator surface area would help dissipate more heat and decide the increase of return temp. Also I don't think it's a situation of needed to increase weather curve (unless maybe it is) as when it's running and maintaining the flow temp of the curve 0.7, it's maintaining temperature in the house. It's just because it can't modulate low enough and then cycles off. I did wonder about pushing the curve a bit higher so it can keep running, but I think we would then be hot.

Thanks for the quick reply and thoughts. Yes I was reading around this but wasn't sure how helpful it would be in this case. I was trying to set up decent monitoring to be able to have data but struggling with that. I don't think it's coming on that strong (I haven't bothered to stand by the box and watch it, but having seen on the app we are hitting ~1500W power input, at lowest compressor speed I see around 950W depending on outside temp. Our unit is quite oversized, while we complete renovations, so we cycle down to 4C. Though we will see -7C overnight quite regularly, and heating off as 15C due to solar gain - so our cycle range of temps is shifted lower. I do think it's cycling well, but if I could get it to pace it's on a bit, I think it might run nicer. I can note the off periods when the temp outside is circa 10C and you can feel the lack of heating I to the house. I guess I could put it in noise reduction mode during the day time and see if it helps. But really I need graphical data first. I would leave it off overnight as we need it to be able to run full to meet potential heat loss at low temps.

Regarding the cycling of the vaillant aerotherm plus, has anyone looked into or got information on the power it starts a cycle with? My machine seems to cycle well, however I feel it comes on at a higher rate than needed which pushes temperature up fast, where as if it started at a low compressor speed it wouldn't rap so fast and on cycle would be longer. Maybe it needs the compressor speed to get going and is just how it is.

Yes! Exactly.

Would you propose using a Flexi to exit the back then? As we need to make a 90deg to enter the building. Perhaps just bend 35mm plastic

Interesting. I guess the UFH has it's own pump, and perhaps your rads are lower pressure drop.

Maybe I'm way off base with these things and I'm happy to be told I'm wrong. Just trying to find a way forward to best alterations to have a 'ideal' base install.

Yes okay thanks for your time explaining that. Looking at a DN32 ESBE 3way, the KVs is 16, so (18.5cV) so the pressure drop would be ~ half or 3.5kpa. I'm not sure that's insignificant. If I'm saying moving from 26mm i.d. to 32mm i.d. primary will reduce pressure from 12 to 4.5 kPa, a reduction of 7kPa.

Yes you're right I am. I have seen others mention using bigger 3ways for bigger pipe. I just wondered if it's better the change what's possible, while there changing pipe, than then try come back later and do it. I'm going around on all aspects to decide what I request is changed and what can stay. Because if we change some stuff and can't hit near 2000 then I'm going to annoy the installer - who just wanted to put a buffer in in the first place (but fitted as volumizer on request), so I'd rather get it right second time and hit as needed.

also what 3 way diverter are you running? Maybe this should be changed on mine to, while we are making changes.

What's the length on you primaries? Mine are 22m total. For sure I also have some loss due to the smaller valves that need changing and the rogue 3m of 20mm id pipe. Plus those plastic fittings are even smaller diameter so add greater restriction.

Thanks that makes sense and yes it's set to 900mbar. I can't see where to find the notice on if it's met. The manual says live monitor can show stays codes but I can't see them or a menu inside to access.

Thanks for the explanation. That's interesting. The graph, which I didn't copy well I re attach. It is 'residual.pressure available'. Page 39 here https://www.vaillant.es/product-images/0020326641-03.pdf.pdf Let me have a think about your point, though I think it would be a case of pushing vaillant to confirm that, after having changed piping. I'm just concerned about pushing the installer to change piping, but not for a buffer, and then still not hitting this magic flow rate. And then having the fit a buffer still, or just not fitting a buffer if we hit a flow rate I deem ok.

Thanks for the explanation. And yes it seems a buffer was initially specified here, because it just makes up for other inadequacies in planned inital install.