ᐅ Current Test Reports on Air-to-Water Heat Pumps

Unfortunately, that doesn’t help much, but I’ve read some tests where only a small selection of devices is usually featured. For example, a colleague recently recommended that I look at Rotex and Tecalor. Tecalor’s parent company is the market leader in climate technology, and an air-to-water heat pump comes from climate technology. I haven’t seen these companies in any of the tests so far.

I am currently also searching for a good air-to-water heat pump, but it’s very difficult. Manufacturers refer to the installers, who know about heating systems but not about air conditioning units. So far, no one has been able to explain to me how an air-to-water heat pump works. Most answers are something like, “It’s similar to a refrigerator, just the other way around.” Okay… but why is there refrigerant? Which refrigerant does an air-to-water heat pump use? No one knows that the current refrigerants are banned and that the much more environmentally friendly R-32 is used in the long term. However, for this top-class advice, companies want around 11,000 for an air-to-water heat pump, which can be delivered online for 6,000.

When I also read that underfloor heating is even more important, I get more and more frustrated, because that will be our responsibility again. I will schedule another appointment with the energy consultant. They seemed competent and might be able to perform the necessary calculations. How would you proceed?

Christian K. schrieb:
Unfortunately, that doesn’t help you much, but I’ve read some tests where only a small selection of devices is usually included. For example, I recently got a recommendation from a colleague to look into Rotex and Tecalor. Tecalor’s parent company is the market leader in HVAC technology, and an air-to-water heat pump is part of HVAC. I have never seen these companies in any of the tests so far.

I’m currently also looking for a good air-to-water heat pump, but it’s really difficult. The manufacturers refer you to the installers, and while they know about heating systems, they’re not familiar with air conditioning units. So far, no one has been able to explain to me how an air-to-water heat pump actually works. Usually, the answer is something like, “It’s like a refrigerator, just the other way around.” Okay... but why is there refrigerant involved? Which refrigerant does the air-to-water heat pump use? No one knows that current refrigerants are banned, and that the far more environmentally friendly R-32 is used in the long term. But for this top-quality advice, companies want to charge €11,000 for an air-to-water heat pump that you can get online for €6,000.

When I also read that underfloor heating is even more important, I get more and more desperate because then that falls on us again. I’m going to schedule another appointment with the energy consultant. He seemed competent and might be able to do the necessary calculations for me. How would you proceed?

Don’t try to find the best heat pump. Choose the one your builder or your HVAC company is at least somewhat familiar with, or at least has a technician on speed dial. In other words, go with what they recommend.

Then make sure the pipe spacing of the underfloor heating is correct. And that the heat load of the heat pump matches what is stated in your energy efficiency report (e.g., KFW assessment). No thermal storage tank and no bypass valve.

Once everything is installed, turn off the actuators on the control units at the heating circuit manifold and switch off the thermostats, change the hysteresis setting from “gas heating” to “heat pump,” set domestic hot water to 41°C (105°F) instead of 60°C (140°F), and then adjust the heating curve until it fits. You will still be surprised by the high water content in the new building and pay about $200 upfront for electricity, but then you can look forward to the following year...

Procedure:

1. Underfloor heating:
a. Discuss individual comfort temperatures for each room (especially the bathroom—does it have to be 24°C (75°F)?)
b. Have the heating load calculated per room according to DIN standards, using the exact U-values of the house
c. Plan the surface heating system to achieve the comfort temperature with a low flow temperature. Keep all circuits around 80 meters (260 feet); do not accept very short or very long circuits.
d. Submit the plans to the heating engineer

A good heating engineer can, of course, handle this independently. It’s safer to have it done separately.

2. Selecting the heat pump and specialist contractor:
a. Choose a modulating heat pump to get a reasonably modern unit
b. Avoid combined units with ventilation, air-to-air, or exhaust air heat pumps
c. No buffer tank, no solar thermal system, no hydronic fireplace, no bypass valves, hot water storage with a large heat exchanger (2-3 m² (22-32 sq ft)), 200-300 liters (50-80 gallons)
d. Dimensioning: use the heating load from the room-by-room calculation without any margins, including ventilation losses. If there is especially high hot water demand, account for it separately. Do not use heating load values from energy or KfW certificates.

If you find a heating engineer who agrees with this, you’re already halfway there.

I would prefer a compact unit instead of a split system, as it reduces complexity and potentially follow-up and maintenance costs—but this is not mandatory.

In conclusion: it is far more important to avoid common mistakes in planning and hydraulics than to find the “best” heat pump.

Therefore, you should educate yourself and not blindly trust the heating installer or manufacturer. There are plenty of articles available in other forums and online.

Thank you very much for the detailed answers.

I have to be honest, the topic of heating is quite intimidating.
As a complete beginner, figuring it all out to avoid ending up with a monthly electricity bill of 400 euros will be challenging.

I don’t understand this either... there are tests for everything... you can even check reviews for doctors, but not for an air-to-water heat pump costing 11,000 (currency).

We chose the one our heating technician recommended and before that, we visited a few people who had installed the same system and asked if there were any problems and listened to the unit... it can be quite loud if the device is low quality.