Interpretation of iDM heat pump regarding COP

Since a heat pump usually almost always operates only in part-load mode (even the somewhat smaller than calculated heat pump), this "problem" occurs only on a few days a year when it is bitterly cold.

But not in domestic hot water preparation, and the iPump gladly does this 2-3 times a day thanks to its integrated 180l mini-tank. What you describe is certainly the case if the heating system is designed for continuous operation. Most heaters leave a heat pump so that it cycles a lot thanks to ERR. In addition, there may be blocking times or setback periods due to photovoltaic electricity. Although this is usually advised against for efficiency reasons, if the electricity is free during the day (more or less) and costs 40 cents at night, efficiency can almost be irrelevant.

But not for the hot water preparation, and thanks to the integrated 180l mini-tank, the iPump gladly does that 2-3 times a day.

Then you’re not allowed to shower 2-3 times a day ;) .

Most installers leave a heat pump in such a way that it cycles a lot due to ERR.
There may also be blocking times or setback periods due to photovoltaic power. Although this is usually advised against for efficiency reasons, if the power is free during the day (more or less) and costs 40 cents at night, efficiency can almost be irrelevant.

That’s exactly why I always preach here in the forum to have the heating professionally designed and to get an exemption from ERR if possible. Then it’s no problem at all. But clearly, for the installer, it’s of course easier to say “we’ve always done it this way and a bit more capacity + buffer tank will work.”

Many heating system users often choose the larger model because they include the hot water preparation on top. A small heat pump simply takes correspondingly longer (or even very long!), which is not necessarily beneficial for heating operation if you make hot water 2x (or even) more times a day.

A small heat pump simply takes correspondingly longer (or even a very long time!), which is not necessarily beneficial for heating operation if you make hot water 2x (or even) more times a day.

Then it is not due to the heat pump (every heat pump nowadays produces 55-60 degrees flow temperature with a proper volume flow), but rather the size of the storage tank and user behavior. Making hot water 2x or more times a day means, with a mini storage tank of +/- 160 liters, that you consume 350 liters or more of hot water every day. How do you do that, except that the four-person family takes four full baths a day?

It's simply about how long a heat pump needs to heat up the hot water tank. The smaller the heat pump, the longer it takes. I've already seen systems where the hot water preparation with a hysteresis of about 5K takes around 2 hours. If you heat up twice, you "waste" a total of 4 hours with hot water!

Also don't forget the heat loss of a tank when idle, without hot water circulation or extraction. It can amount to 3-5K within 24 hours!

I have already seen systems where the hot water preparation with a hysteresis of about 5K takes approximately 2 hours.

Wow, how damn poorly these systems are designed. Even the smallest Pana monoblock needs only about 45 minutes for around 10 degrees hysteresis – with a 300-liter tank. For me, with 5 degrees hysteresis, it takes about 20 minutes for 300 liters. But: properly planned and with sufficient flow rate (that can also be 20 liters/min).