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In Bad Waldsee, one of the sunniest spa towns in Germany, holidaymakers will find the accommodations offered by the Schmid family. With the intention of benefiting from tourism, the family built a house with three apartments near their farm. They chose an air-to-water heat pump to heat the building. 



The technical building system is just as modern as the flats decorated in a tasteful contemporary style: The house receives heat from an air-to-water heat pump. The 8 kW Ecodan heat pump made by Mitsubishi Electric is the sole source of heat. The environmentally friendly energy generation was the deciding factor. Another reason is the photovoltaic system on the roof of one of the buildings used for agricultural purposes. “This way we can generate some of the electricity needed ourselves and use it sensibly,” says the farmer.


When choosing the best system for their needs, the Schmids made efficiency a priority. The Ecodan system was the logical choice for them. With its globally patented Zubadan technology, the heat pump supplies 100% heating capacity even at subfreezing temperatures as low as -15 °C. And the manufacturer guarantees proper functioning even at -28 °C. This is why the system can be operated in monovalent mode, eliminating the need for an electrical heating rod or fossil fuel-based peak load device.



Another aspect that contributed to choosing the heat pump is the quick installation. Because there are no gas lines on the outskirts of Bad Waldsee where the house is, alternative energy sources would have required much greater effort to install. A liquid gas or oil condensing boiler would have required a storage tank, and a pellet heater would have meant finding space to store the pellets. And a chimney would have had to be built, which would mean future expenses for cleaning and inspection. In contrast, the outdoor unit of the heat pump could be easily and quickly installed next to the building. Refrigerant lines connect it to the indoor module in the utility room. 


The system started running during construction: It has a special program to dry screed more quickly. “That worked really well. The heat pump dried out the whole house,” reports Edmund Gresser, proprietor of the specialised crafts business of the same name. The program is just one of many that can be set on the controller in the indoor module. 

Air-to-water heat pumps are an ideal source of heat generation in new buildings, with their thick insulation and floor heaters with low flow temperatures. Under these conditions they work extremely efficiently and also meet the legal requirements specified by the German Energy Saving Ordinance (EnEV).

The primary energy factor for electricity was reduced to 1.8 at the same time, making it easy to achieve the required reduction in primary energy demand with a heat pump. The technology also meets the requirements cited in paragraph 3 of the German Renewable Energy Heat Act (EEWärmeG), dictating that owners of new buildings with more than 50 m2 of usable floor space have to ensure that part of the energy needed to heat and cool the facility comes from renewable energy sources. 



The heat pump is equipped with full inverter technology, allowing the output to be variably adjusted to the current need. So the system works much more efficiently than systems with only on and off modes, meaning systems that work at 100° capacity or not at all. In addition to the outdoor unit and indoor module, a 200 litre buffer tank was installed as well. It provides enough energy to defrost the heat pump and increases the efficiency of the system by optimising the compressor operating times. 


The system is programmed such that the basic heat is supply via an outdoor temperature controller. “Thermostats in each room of the flats allow the guests to adjust the temperature to their liking,” states Schmid. The intention is to rent out the flats all year round, if the demand is there. In the winter the heat pump supplies energy for the heater and domestic hot water, and in the summer for domestic hot water.



Several years ago, the Schmids purchased a photovoltaic system and collectors with a total capacity of 30 kW to produce electricity for their own household and for the farm. An investment that had paid off. The farmer can generate the electricity needed for the heat pump himself with the system – either all or some of it. 


“Our home consumption is about 40 percent right now. I was pleasantly surprised that we can use so much of the electricity in our own household and for the farm,” says a happy Mr. Schmid, “And with the holiday flats and the heat pump our consumption will rise, so we will only be feeding a little bit into the grid.” During the warmer time of year the electricity needed to heat the domestic hot water will be supplied exclusively by the photovoltaic system. 



The Schmids thought about whether a battery for storing electrical power makes sense. “But we decided to wait until the price of the batteries goes down some,” states the homeowner. With the right storage device, the new building can achieve an almost completely self-sufficient energy supply. And the electricity and heat needed are generated completely by the regenerative energy sources sun and air. “So the combination of heat pump and photovoltaic system offers not only financial benefits, it is also the ideal solution from an ecological point of view,” emphasises Schmid. 



In order to benefit from environmentally friendly and efficient energy production, the Schmid family decided on an Ecodan air-to-water heat pump that not only heats the three holiday flats but also produces domestic hot water. The electricity needed for the heat pump system is generated by the photovoltaic system that the family installed a few years ago.


An added benefit: Installation of the heat pump was much simpler and less expensive than other heat generators, because it required no storage space for fuel and no chimney. Plus it could be used during construction to dry the screed. And last but not least, it meets the requirements of the German Energy Saving Ordinance (EnEV) and the German Renewable Energy Heat Act (EEWärmeG).