AIR-TO-WATER HEAT PUMP IN EXISTING BUILDINGS
The bivalent air-to-water heat pump in the Hielschers’ single-family house heated the home for 34 years. Then it suddenly broke down. Replacement with a modern system was quick and brought lots of improvements. The new system is monovalent and the old oil-fired boiler is no longer needed. The Hielschers are delighted with the final result and enjoy the pleasant, consistent heat generated efficiently and ecologically with the new system.
Modern and conventional technologies stand side-by-side in the Hielschers’ home: Besides the oil-fired boiler and two oil tanks in the boiler room, they have the outdoor unit of an air-to-water heat pump by the house wall. The two heat generators heated the 170 m2 single-family house, built in 1966, for 34 years. It was an unusual combination at the time: Even in new construction, heat pumps were not nearly as common as they are today.
But Norbert Hielscher was interested a long time ago in this efficient and environmentally friendly way of producing energy. “I read brochures and looked at a system at a trade fair,” remembers the homeowner. As a professional electrician, he quickly realised that an air-to-water heat pump would work economically in a well-insulated Okal prefabricated house, making it a sensible investment. I installed and started up the monoblock device myself,” says Hielscher.
AFTER 34 YEARS
A NEW SOLUTION
Because the heat pump could only supply enough heat to the building at an outside temperature of 2 °C, a second heat generator was needed. The Hielschers decided to combine the existing oil-fired boiler with the heat pump. Then a year and a half ago they were suddenly confronted with a heat pump that no longer worked. “Because the pump used the refrigerant R22, we were not allowed to repair it,” explains Jochen Reuter, project manager at elektroma GmbH in Hameln. There were two options: either monovalent use of the oil-fired boiler or replacing the heat pump with a newer model.
Hielscher knew right away that he would stick with the modern technology. And he was definitely not giving up the air-to-water system. Reuter proposed the Ecodan system by Mitsubishi Electric to the homeowners for their renovation. The new heat pump has a distinct advantage over the old device and other models on the market. The Zubadan technology enables the system to supply 100% heating capacity at subfreezing temperatures as cold as -15°C. And the manufacturer guarantees proper functioning even at -28°C. This is why the system can now be operated in monovalent mode, eliminating the need for an electrical heating rod or the additional oil-fired boiler.
Planning the new system, dismantling the old heat pump and installing the new unit took only a few days. “It really was quick,” reports Hielscher. And we hardly noticed the work going on, because it was only outside and in the boiler room.” The new system was up and running after three days. The 11.2 kW outdoor unit replaced the old 10 kW heat pump next to the house. Hidden behind bushes and shrubs, it is nearly invisible from the street. Since the chosen system can handle line lengths up to 80 metres, the location for the outdoor unit can be selected to best suit the conditions on site. For example, it could also be placed at the edge of a property.
SPLIT PRINCIPLE WITH
OUTDOOR UNIT AND INDOOR MODULE
Reuter recommended the split principle to the Hielschers. Unlike the old monoblock heat pump, there is an indoor module in addition to the outdoor unit. The plate heat exchanger is located in the indoor module and the outdoor unit is connected via a refrigerant pipe. This means that the lines do not have to be insulated to protect them from frost, and hardly any energy is lost in transit.
Planning the new system, dismantling the old heat pump and installing the new unit took only a few days. “It really was quick,” says Hielscher. And we hardly noticed the work going on, because it was only outside and in the boiler room.” The new system was up and running after three days. The 11.2 kW outdoor unit replaced the old 10 kW heat pump next to the house. Hidden behind bushes and shrubs, it is nearly invisible from the street.
No changes had to made to heat distribution. The chosen system works efficiently even at high flow temperatures up to 60 °C. That is enough to supply sufficient hot water to the classic radiators in various sizes throughout the house. “This is why the Ecodan system is so well suited for renovations,” explains Reuter.
The efficiency of the new system and the monovalent use mean that the Hielschers will be saving money. Once the rest of the oil is used up, the tanks and boiler will be dismantled. This not only frees up space in the boiler room, it also eliminates the cost of inspecting and cleaning the chimney.
The heat pump system is regulated with a remote control that the Hielschers keep in the lounge. The user-friendly, self-explanatory symbols on the keys make adjusting the temperature quick and easy. Pre-defined programs like holiday mode can be set as well. “It is really easy and works well,” says the homeowner.
And he is very satisfied with the system’s automatic control: “The temperature is always the same, so it is pleasantly warm even on really cold days.” The controller for the new system is much better than the old device. Reuter made the setting such that the probe senses the indoor and outdoor temperature and adjusts heat output accordingly.
Norbert Hielscher is a heat pump pioneer. He chose this technology way back in the early 1980s. But since the pump only worked at temperatures down to 2 °C, an oil-fired boiler was needed to keep the house warm. After 34 years, the heat pump was defective and had to be replaced. The new Ecodan system has a distinct advantage over the old model: Since it can heat at 100% even at double-digit subfreezing temperatures, the heat pump can run monovalently. This not only reduces operating costs, the Hielschers will have more space in the cellar when the oil-fired boiler and tank are removed. The homeowners are very happy with the upgrade. They are enjoying the comfort of consistent heating on really cold days and the ease with which the heat pump system is operated.