Dimplex heat pump settings

Hello everyone,

we bought a house with a heat pump, so we took over all the settings from the previous owners.
I’m not really familiar with it yet, so please always question my statements, but I have the feeling that not everything is ideally set. Several things have immediately caught my attention or are unclear, let’s see if all of this fits into one thread.
We have a heat pump from the company Dimplex, a LA17TU. In the basement there is a Hydrotower HWK 332 Econ with heat pump manager. It would be great if someone knows the system.

First question: In the advanced settings you can specify a threshold for the 2nd heat generator (i.e. the heating element).
The explanation in the manual says "The 2nd heat generator is only required from a certain threshold temperature depending on the dimensioning of the heat pump. The 2nd heat generator is only activated at temperatures below the set threshold temperature."
A threshold temperature of -5°C is set. That would mean the heating element runs always below -5°C, right? Isn’t that set very high? At -5°C, the heat pump should still deliver enough performance without the need for the heating element with its high consumption. On the other hand, the manual indicates the adjustment range as "-20°C ... -5°C ... +20°C", with -5°C in bold, making it look like a standard value.

Second question concerns the heating curve.
There is a section in the manual about optimizing the heating curve. According to this information, the heat pump is controlled by return temperature. In the menu, under the heating circuit settings at "Temperature sensor", you can select "flow" or "return". Here "flow" is selected. Doesn’t that contradict the statement that the control is based on return temperature? Maybe it means something else though.

The heating curve endpoint also puzzles me. According to the internet, our local norm outdoor temperature is -14°C. Is the heating curve endpoint really only dependent on the norm outdoor temperature and not on the structural conditions?
If I look at the table and the family of curves in the manual, an NOT of -14°C corresponds to a required return temperature of 28°C, resulting in a heating curve endpoint of 29°C, which must be set on the device. The actual temperature level in the house should then be adjusted by shifting the curve in parallel. However, the heating curve endpoint is actually set to 45°C. I’m hesitant to make such a large change without knowing exactly what it causes. Should structural conditions perhaps be considered here after all?

Regards,
TObi

Does no one have an idea about this? What else I noticed: This year we waited relatively long to wake the heat pump up from summer mode. It was quite cold inside the house and outside. Room temperature about 17 °C, outside maybe 12 °C, I don't remember exactly. When I simply set it to Auto, which is the mode for winter, it didn’t start at all; only when I significantly shifted it towards warmer did something happen. Now, the setpoint for the underfloor heating circuit (I'm not 100% sure if the supply or return flow is shown, logically it would be the return flow?) is, for example, at 28 °C. It heats to this setpoint once and then the heat pump switches off again, the actual value then drops quite far over time, down to about 20 °C, meaning the water, which is well below the setpoint, is pumped through the pipes. It then takes quite a while until another heating cycle comes that heats up to the set temperature. Sensible? I don't think so. Temperature inside the house is okay though.

The hysteresis is probably set too high! I have a Dimplex li9tu running in my house myself. So far, the additional heating element has never been used here! However, the domestic hot water in my case is never heated above 50°C and the heating water is a max of 35°C when it is -20°C outside. if you want, we can exchange ideas.

Generally:
I don't know your heating system. You need to read up on it. Normally, the manual (also the one for the technicians, if available!) explains a lot.
Moreover, everything depends on the hydraulics. Have you done a balancing? EER deactivated/ always open? ÜSV - if present - closed?

First question

Just try it. What could happen? If it’s 10 degrees for 2 weeks and the compressor can’t manage it, you simply turn it back on.
So deactivate the heating element.

Second question

I run with 100% return flow, seems more sensible to me as that is the slower control value.
Also just try it out.

The endpoint of the heating curve also puzzles me.

Me too. Does it set the slope? If yes: just try it. It can only get too warm or too cold. You have to get familiar with it. Observe, understand, adjust.

What else I noticed

Generally, long heating cycles are desirable. For that, you need a slow control.
The disadvantage is, if too slow, that you have large fluctuations in indoor temperature.
Here you have to find the right setting for yourself.

When I look at the table and the family of curves in the manual, a NAT of -14°C corresponds to a required return temperature of 28°C, which then results in a heating curve endpoint of 29°C that must be set on the device. The actual temperature level in the house is then supposed to be adjusted by parallel shifting of the curve. However, a heating curve endpoint of 45°C is actually set. I am still hesitant to make such a big change without knowing exactly what it will cause. Are there possibly structural conditions to be considered here?

45°C is way too high. I have a Dimplex brine heat pump, and my heating curve endpoint is set at 32°C. The interaction between endpoint and parallel shift needs to be tested, but the manual explains quite well under which conditions which value should be adjusted. Deactivate the heating element and see what happens. If the heat pump really can’t manage at some point, it can be manually reactivated within a minute. Return flow control is usually correct. Maybe your observation is due to no or too short (heating circuit) pump lead time being set.

Thank you for the answers.
happy to exchange.
I have now set the curve endpoint to 30°C. However, it is currently too warm outside to do much testing. There is a second small heating circuit with a few radiators attached, and I have also lowered the endpoint there.
I set the threshold for the 2nd heat generator to -15°C, so if that is the setting for the heating element to kick in, it should now only do so very rarely.

I have to say, we have a large house with 200 sqm of living space from the 80s, which is insulated as poorly as it was done back then. In recent years, 12,000 kWh of heating electricity has been consumed.
I am also working on improving the insulation, but I have the feeling that you can also save something through the settings of the heating system.