ᐅ Air-to-Water Heat Pump – Monoblock or Split System? SCOP / COP

Hi,

we are about to commission the shell construction.
The topic of air-to-water heat pumps is still an issue we haven’t resolved, regardless of availability.

Initially, a split system by Ochsner was planned, with the outdoor unit installed on the garage roof. The pipes would run entirely inside the house down to the basement, with a length of about 13m (43 feet), including a 6m (20 feet) vertical rise, which meets Ochsner’s specifications. (The garage roof was chosen because there is enough space for the outdoor unit and it is far enough away from neighbors to avoid noise disturbance.)

Our plumbing and heating installer offered a Kermi x-change dynamic 8 AW E heat pump. The installation would now face the neighbor’s side. The description states that it operates very quietly in whisper mode. I imagine that when they say whisper mode, it means it becomes loud in normal mode – which is when it runs efficiently.

What is the Kermi like in reality? I couldn’t find any pictures on Google, only marketing images from their PR department. I have already seen a few Ochsner units.

I was told that the SCOP value is more meaningful than the COP value alone, which only shows performance under optimal conditions. I once found a website where you could display many heat pumps in a table showing their (S)COP values, but unfortunately, I cannot find it anymore.

What is your question? Is it just about the appearance of the heat pump?

Whisper mode is available on all heat pumps. In this mode, the output is limited, and the unit operates even more quietly. It can be used whenever full power is not required.

Questions are:

• Which construction types are more efficient, monoblock or split units?
• Appearance in terms of how the units actually look when installed; real photos of installation sites. Online, I only find 3D rendered images showing how they might look.
• Quiet operation— is that just marketing, or are they genuinely consistently quiet? To me, it sounds like the neighbor might hear it running from their balcony or bedroom at night and could complain—and at that time it operates quietly but does so poorly. So, conversely, in normal mode, when it’s supposed to heat my house and provide hot water, the unit runs so loudly that it later has to switch to quiet mode to appease the neighbors? I know the Ochsner split units where you can hear a pin drop even when running at maximum power.
• I once found a website listing heat pumps where you could compare the devices. That site also showed (S)COP values. Maybe someone knows it.

schaaaf schrieb:

Which type of heat pump is more efficient, monobloc or split units?

Basically, it doesn’t matter. There are no noticeable differences for you.

schaaaf schrieb:

What about their appearance, how the units actually look when installed? I only find 3D renderings online showing how they might look.

Go to new housing developments near you and take a look. Most have heat pumps installed. Boxes of all kinds are placed near the entrances. It’s similar to comparing smartphone designs—they basically all look the same.

The Kermi model is quite a bulky unit...

schaaaf schrieb:

Whisper mode—is that just marketing, or are these units truly consistently quiet? To me, it sounds like the neighbor might hear it running in the evening on their balcony or in their bedroom and could complain. Maybe it runs quietly during those times but only performs poorly, whereas in normal mode, when it’s heating my house and providing hot water, it’s loud enough that it needs to switch to whisper mode afterwards to keep the neighbor calm? I know the Ochsner split unit—I can hear ants farting, but it’s running at maximum power.

Whisper mode is not just marketing. Like a car engine is louder at 6,000 rpm than at idle. For example, I have never used whisper mode on my Panasonic monobloc because the heat pump is already quiet enough. The tenant above me has the heat pump located right under her bedroom window—it can only be heard as a gentle hum at full load (at night, with the window slightly open). Last winter, it never actually had to run at full capacity; that only happens when temperatures drop well below freezing.

So, you can use whisper mode about 90% of the time. Much more important is selecting the correct installation location and properly decoupling the heat pump. Many issues arise when mounting it on wall brackets.

schaaaf schrieb:

I once found a website listing heat pumps where you could compare units. They also showed (S)COP values. Maybe someone knows about it.

Those are all just theoretical values on paper. I wouldn’t rely on them. Like a car’s fuel consumption figures—they’re only a rough guide and don’t reflect real life.
Go to heat pump user databases where real users report their actual consumption in real houses. I find that much more helpful.

Thank you, very insightful!

The heat pump consumption database looks interesting. I immediately found someone nearby who is using the Kermi system and has shared their previous data.

schaaaf schrieb:

Which type of system is more efficient, monoblock or split units

If you want to maximize the efficiency of your heat pump, it is important to start with a thorough overall plan. Before selecting the heat pump itself, the design of your underfloor heating system should come first. Since many heating installers still tend to use standard, off-the-shelf solutions, it is advisable to educate yourself on the topic.