Air-to-water heat pump sizing in new construction

The buffer tank is only needed if you have individual room control. If you leave both out, which is very, very sensible for the efficient operation of the heat pump, you pay much less money. You can find help in the [HTD-Forum]. The heating engineer will say that the heat pump cannot defrost without a buffer. Then you say: "I have always kept all heating circuits open, so there is more than enough water." Regarding the size of the heat pump: You only choose it once you have the "room-by-room heating load calculation." Have it prepared and handed over to you by whoever. The person who calculates the underfloor heating needs it anyway (if not, they are doing it wrong!). Then choose a heat pump that fits as best as possible. NOT bigger and also WITHOUT an extra margin for hot water.

The buffer tank is only necessary if you have individual room control....

Did I misunderstand until now that nowadays in new buildings you are no longer "allowed" to do without the IRC?

Had I misunderstood so far that nowadays in new buildings you are no longer "allowed" to do without the ERR?

That's already true in construction (exemption is almost impossible). But afterwards, no one forces you to disable the controllers and run the heating "fully automatically." Which, by the way, is often recommended.

That is already true during construction (exemption is virtually impossible). But afterwards, no one forces you to disable the controllers and run the heating "fully automatic." Which, by the way, is often recommended.

That is also my understanding so far. However, it would mean that everyone would also have to be forced to take the buffer tank, since it is required with ERR…?!

I simply do not understand this deviation between theory and practice among the craftsmen.

Theory: 4 heating circuits with 15cm laying distance:


Practice: 6 heating circuits with 10cm laying distance:


Heating circuit distributor:


Sometimes I wonder if they are doing it on purpose? We are talking all the time about how it should be done and the general contractor complains about the warranty, and then everything is done differently? This is getting on my nerves a bit right now. I just wonder whether it is justified or if I should just let it go.

The flow rate according to planning should be 1.45 l/min. Now I should be able to throttle further to about 1 l/min?

15 cm would have been nonsense anyway. 10 works. But why is there a free area at the bottom left?

And yet – there are several reports from people who have had themselves freed from ERR. If that doesn’t work, make sure the actuators are powered off and open. Then you can simply unplug the cables. It’s of course a shame to throw money away on that... If you then have no chance to persuade the heating technician to go for a buffer-free system, at least have a small (50l) buffer installed in series in the return line. Not parallel as a bypass. That way, you never have the chance to pump cleanly and heat without loss. Two evenings in the HTD forum and maybe an hour of discussion can save several thousand euros in investment and just as much in electricity costs over the operational period. It’s worth it.