ᐅ Heating with an Air-to-Water Heat Pump with Cooling Function

Hello everyone,

we are currently planning our house. One of the first questions from suppliers is always about the "heating method."

So far, I have mostly shrugged and said "gas heating."

Over the weekend, one supplier recommended air-to-water heat pumps. Until now, I didn’t even know such systems existed.

I’m trying to educate myself a bit and found the following model from the company "Stiebel Eltron":

WPL 13-23 cool

The description says it can be used for both heating and cooling.

Now my question:

Can the cooling function be understood like an "active" air conditioning system (performance of a split air conditioner), or is it more of a kind of "pseudo cooling" that lowers the building temperature from 35°C to 34.5°C (95°F to 94°F), meaning almost no real cooling?

What do you think of this technology in general? (I have only lived in houses/apartments with gas heating so far)

(Warm in winter with gas, cool in summer with a separate air conditioner)

I want it to be warm in winter (without having to wear a thick sweater indoors) and cool/cold in summer.

Until now, I have never really looked into energy efficiency.

In winter, I prefer a (very) "warm house" and rather pay extra than be cold and get 100 euros back.

With friends and acquaintances who have installed "new" technology, I often get the feeling their house is (too) cold in winter. (You don’t freeze, but it’s not comfortably warm either.)

When they visit us, they almost always say, "Oh, it’s so nice and warm here."

Best regards

Bubb

Hello Bubb,
1. First, regarding the manufacturer Stiebel Eltron. In my opinion, you can get the same quality for less money from Mitsubishi Ecodan or Daikin.
2. I would never use a heat pump for cooling.
- Risk of mold growth (cold floors or cold walls),
- What happens if you want hot water and cooling at the same time?
- For that, there are regular split systems.
3. You can only save effectively with a heat pump if you have a low flow temperature (max 35°C (95°F)), which can be achieved with relatively large radiators or underfloor heating. Then you can at least halve your heating costs.
Many of my friends have heat pumps, and if you choose a reliable manufacturer, properly size the air source heat pump, and consider everything during installation, then energy savings work well and the house stays warm.

Hello Maxim,

Thank you for your reply,

What concerns me now are the many "ifs" (if the right manufacturer, if installed correctly, etc., then the house will be warm).

Does this mean that it is basically a gamble?

As I mentioned, I currently have zero knowledge about this. (The fact that every provider says or recommends something different doesn’t make it any easier).

I’d rather stick with gas, so the house is definitely warm.

You’re right about cooling. Since we are planning underfloor heating, the floor would be cold when cooling (I hadn’t thought that far).

Regards,

Bubb

Hello Bubb,
There aren’t many ifs and buts; I am planning my house with underfloor heating and an air-source heat pump. According to the architect, the energy demand is 8 kW, so I will choose an 11 kW heat pump from Mitsubishi or Daikin, as they can automatically adjust their output. I will also use a large buffer tank to reduce the frequency of switching on and off, which saves energy. The flow temperature will be 28°C (82°F), which also leads to 10-20% energy savings. The good thing is that I can do without solar panels because on sunny days the air-source heat pump operates even more efficiently.
That’s all I considered for the system design.
Underfloor heating usually makes a heat pump worthwhile.
Regards,
Maxim

Hello,

Bubb schrieb:
Can the cooling function be compared to an "active" air conditioning system (performance similar to a split air conditioner), or is it more like a kind of "pseudo-cooling" that lowers the building temperature from 35°C to 34.5°C (95°F to 94.1°F)? So, almost no real cooling? What is your opinion on this technology?

All manufacturers claim that air-to-water heat pumps can also be used for cooling, but in reality, you can only expect a temperature difference of about 2-3 degrees; so rather separate systems—either an additional air-to-air heat pump or, more cost-effectively, strategically placed air conditioning units. Another drawback of air-to-water heat pumps with cooling is that condensation can form on tile floors, creating a slippery surface when wearing certain footwear.

Bubb schrieb:
With acquaintances and friends who have installed "new" technologies, I often feel in winter that their houses are (too) cold. (Not directly freezing, but not cozy warm either).

This is usually not due to the new technologies, but rather the German favorite pastime: “Oh, it’s warm outside, let’s turn the heating down,” forgetting that nowadays every heating system adjusts itself based on the outside temperature and regulates accordingly. Also, these new systems do not respond well when their settings are constantly being “tweaked.”

My recommendation: one system for heating, optionally combined with ventilation if there is enough space in the utility room, and a separate system for cooling.

Kind regards

Hello,

Maxim schrieb:
..., I am planning my house with underfloor heating and an air source heat pump. According to the architect, the energy demand is 8 kW, but I will use an 11 kW heat pump from Mitsubishi or Daikin because they can regulate their output independently.

This is not particularly sensible. Is this stated in the heating load calculation according to DIN 12831? Also, take a close look at the COP and heating capacity curves of the mentioned devices; you might notice something about the modulation.

Maxim schrieb:
...The supply temperature will be 28°C (82°F)...

What is the surface temperature at that supply temperature, considering the room temperature and the type of floor covering? Don’t forget the heat loss downward!

Best regards.