Hi everyone!
Please move this topic to the right forum if this is not the one.
I live in a 300sqm ish detached house in the centre of Spain, 1990 built with upgrades to the insulation along the way. Heating to 21-22 degrees.
Last October I was fitted a mega 16kW Altherma 3 hydro-split. They did not do heatloss calculations that I could see (I did not have the knowledge back then that I do now) and I ended up with an oversized unit. For context, the most I have seen it produce on a given winter day was 200kWh (it procuded 3900kwh in the coldest month, only), so about 8.3kW. Granted, it was not the coldest of winters but I think we can all agree it is grossly oversized.
They also replaced 7 of the radiators with heatpump convectors, but they used Multilayer tubing ( PERT-AL-PERT), to connect everything to the existing 22mm main, 12/15mm copper pipework. This has restricted the flow, which I did not know at the time.
Anyway, they fitted a 100L buffer tank and a Yonos Pico 1.0 30/1-8 circulator pump, after I got them to swap the original 25/1-6 unit, which was heavily undersized for the pipework and all the small bore multilayer piping they installed.
After a lot of tweaking, I got the system to work well enough in heating (SCOP reported by the unit January-April of 4.65), but it does cycle a lot. I limited it by setting 30ºC minimum flow and using the Madoka as a cut-off (no modulation, so that it does not heat to 23.5!). At mildest temps, it maybe cycles 2 or 3 times per hour. I was happy enough with that, as the reported COP was around 5 in those instances.
Well, now summer is approaching and we want to use it for cooling (main reason why we installed it). After closing the radiators, to only use the heatpump convectors, the volume of water in the system and dissipated kWs have been reduced, and it is cycling like mad. Due to humidity, I cannot push LWT lower than 12ºC for now (crap job at insulating by the installer), to avoid condensation, so I am stuck with until humidity levels get lower during summer hopefully.
The result of above is that it is cycling a LOT (4 times an hour, maybe 5), which I am not happy about at all.Cycling as of yesterday:
I want to improve both cycling and cooling performance, which have me thinking of the following options:
1- Replace the 100L buffer with a 300L buffer tank. This should increase heating/cooling cycles length by at least 10-15 minutes according to my calculations.
2a- Re-pipe the buffer as a 3-port:
This would hopefully achieve that the heatpump convectors inlet temperature match LWT, thus gaining 1 or 2 degrees and therefore increasing output (more cooling!)
2b- Re-pipe the buffer as a volumiser in the return line. The problem that I can see is that maybe the Daikin internal pump will not achieve enough flow for de-frost operation due to the restrictive pipework. I have compared both the Daikin pump chart and the Pico pump:
Yonos Pico 1.0 30:
Daikin 16Kw EBVX16S23D6V:
The Daikin pump appears to be more powerful, so it should achieve better flowrate. At the moment, during cooling, the Pico screen shows 69W power consumption, which based on above would mean a flow rate of about 24l/min? Therefore, the Daikin should achieve more than that, but I do not know if I want to risk it.
On the long run, we will repipe as much as we can to increase flow rate, but that is major work in this type of house.
Thanks everyone for the inmense help!