Mark_xx
2023-10-30 14:32:29
- #1
Hi,
as far as I can see on IDM's website, this is a combined storage tank installed as a hydraulic separator. There is a separation of the heat pump circuit and the heating circuit. That is not good!
Such an installation makes sense with a high-temperature heat generator and a low-temperature heat sink, such as underfloor heating.
With a heat pump, the goal is only to produce the required amount of heat, i.e., to adjust the flow temperature to the needed demand. With a design that includes a buffer tank/combined storage tank, you would have to match the volume flow of the heating circuit (underfloor heating) as precisely as possible to the volume flow of the heat pump; only then do you have low energy loss through the design of the buffer tank. However, the offered heat pump is a modulating heat pump, and that is actually correct. The problem with buffer tanks is the adjustment of the volume flows. The heat pump controls not only the compressor output but also the volume flow to always have the optimal temperature difference in the heat pump circuit. However, the circulation pump of the heating circuit operates with a fixed volume flow. Therefore, the volume flows cannot be optimally coordinated; there is ALWAYS an efficiency loss!
The solution is to run the heat pump directly to the underfloor heating; for this, to ensure the minimum volume flow, enough heating circuits must always be open (disable ERR). To produce domestic hot water, a three-way valve switches from the underfloor heating to the domestic hot water tank. A small buffer tank (30-70L) can be planned in the heat pump return flow to ensure defrosting cycles. Although it is not necessary since the screed provides more heat for defrosting than a buffer tank, at least then the efficiency loss can be neglected.
Conclusion:
1. Have a heating load calculation done.
2. Then have a SMALL heat pump offered accordingly; do not accept a safety margin in heating output as the heating load calculation already covers that. No buffer tanks/combined storage tanks or similar designs.
3. It is also important to calculate the heating load per room and then design the underfloor heating accordingly, including temperature specifications for the individual rooms. If necessary (usually in bathrooms), consider additional wall heating. If towel radiators are planned, do not integrate them into the heating circuit but operate them electrically.
After moving in:
4. In the first winters, perform the thermal balancing of the rooms (not via the ERR!); this is a do-it-yourself task and not to be done by the heating engineer.
5. Regularly check operating behavior and cycle times.
Greetings from Hamburg
Thank you very much for your detailed response!
I have already requested the heating load calculations.
If I want to stay with iDM now, would your recommendation be to choose the Aero ALM (2-8) model and combine it with a domestic hot water tank?
The hygienic storage tanks alternatively offered by iDM are ultimately also combined storage tanks with similar problems as you described, correct?
Basically, I would have liked the concept of a heat pump with an integrated combined storage tank because space is quite limited, but maybe space-wise it also works with an AERO ALM and a domestic hot water tank.
Best regards from the south!