Interaction between air-water heat pump and gas condensing boiler?

Hello,

The apartment building has 25 apartments and the gas condensing boiler is only supposed to be used when it is really cold outside and in the morning, when maybe everyone wants to shower warm at the same time.

Then that sounds to me, without being able to calculate it now, like a quite sensible solution. Otherwise, the heat pump would probably have to be significantly larger.

But how does a heat pump manage to heat the water continuously to 60 °C?

Very simple: it doesn’t! That is done by an electric heating element = electric heater. According to DIN, the heating element is not included in the calculation of efficiency either, otherwise the efficiency would look pretty bad.... ;-) The same applies to most heat pumps at -10 degrees outside temperature, then it’s game over, they only run 1:1 as an electric heater. (Yes, there are also heat pumps that can reach significantly more than 45 degrees water temperature without a heating element and still run at -10 degrees. But these are not the normal run-of-the-mill heat pumps)

Best regards,

Andreas

In such cases, fresh water stations are probably more sensible. They have no Legionella problem and you save the high temperatures. Currently, the relatively new monoblocks with propane as a refrigerant would still be an option. They heat up to 70° without a heating rod, can cascade, and are supposed to go up to 26kW soon. Since photovoltaic systems in apartment buildings are still not really practical anyway, solar thermal energy might actually be really useful here... But the topic is exciting – I also own part of an apartment building and the heating system is getting old...

Quite simple: not at all! That then runs via a heating element = electric heating. According to DIN, the heating element is also not taken into account in the calculation of efficiency, otherwise the efficiency would look pretty bad.... ;-) It’s the same with most heat pumps at -10 degrees outside temperature, then it’s game over, they only run 1:1 as electric heaters. (Yes, there are also heat pumps that can reach significantly more than 45 degrees water temperature without a heating element and that still run at -10 degrees. But these are not the normal standard heat pumps)

But hardly anyone does 60 degrees in the single-family house sector. However, most heat pumps approach up to 60 degrees - without a heating element.

And if a heat pump needs the heating element at -10 degrees outside temperature, something went wrong with the planning. Normally, you can simply turn off the heating element (except in exposed locations like mid-mountains) – I did that too (it only switches on for defrosting).

The heat pumps that can do that are completely normal standard devices. You don’t need high-tech devices for that. My €3,000 heat pump handles this without problems (60 degrees flow temperature + -20 degrees outside temperature without heating element).

(he only kicks in for defrosting)

Why is that? You should have more than enough energy in the heating water?!

Why is that? You should have more than enough energy in the heating water?!

It is a preset of the heat pump. It cannot be bypassed. If I cut off the power to the heating element not only control-wise (in terms of heating support) but also hardware-wise (removing the fuse), the system goes into fault mode. So I have to live with it possibly turning on the heating element for a few minutes.

Hm. Fancy. I would be interested in the technical background. I personally know five heat pumps of different years of manufacture – three of them don’t even have a heating element and still defrost. May I ask for the model?