Assessment of calculated heating load values according to the sanitary technician

Hello everyone,

I had the heating load for my house calculated. Unfortunately, the result is exactly between two devices... Beforehand, a central controlled residential ventilation system with heat recovery is planned.

Here is the statement from my plumbing specialist:
The calculated heating load is approximately 5.6 kW at -10°C. The air heat pump produces about 5 kW at this time, the remaining 0.6 kW is covered by the heating rod. (The next larger device produces about 7 kW heating capacity at -10°C.)

Your possible hot water withdrawal (continuous output) is approximately 254 liters per hour.

These are technical details and now I wanted to throw these values into the group. What do you think of the statements? I live in the Ruhr area, it does get cold here too, -10°C happens less often, but there have been exceptions with -20°C. Would you agree with this statement or tend rather toward the larger device?

Thank you very much and I hope these details are "sufficient"...

Best regards splitti

Hello,

Who calculated the heating load for you??
Does the ventilation system have a post-heating coil, pre-heating coil, brine preheater, or is the outside air duct buried??
To what extent was this taken into account in the heating load??
What room temperature was used???

I know the Ruhr area from the map and have been there once so far, so I cannot estimate whether it stays cold for a long time (foggy is what I have in mind it often is).

What you must not forget: one thing is the heating load, another is the domestic hot water preparation. If you need hot water now, the energy supply for the heating stops. Depending on the size of the hot water tank, it can take some time until the domestic hot water preparation is finished and the heat pump is available again for heating (and in the meantime, you operate your heating with the electric heater).

The decision is not an easy one and, in my opinion, also depends on how often this is to be expected. For this reason, I have an air-water heat pump that goes down to about -16°C without the electric heater in my case; only below that does it become active (this winter about 6 times, but in total less than half an hour). However, my climate is significantly more "brutal" – design heating load at -14.6°C, every winter down to -20°C, often in such a way that during the day it only rises to -10 degrees or warms up.

If you have the possibility to add additional energy with the ventilation (independent of the heat pump) and it only briefly gets that cold, I would take the smaller one; otherwise (depending on the price difference) the larger one (a COP of about 2.3 at -16°C to +35°C is still better than direct heating with an electric heater).

Best regards Christian