Cutting-edge heating solution in a renovated farmhouse
Ecodan air-to-water heat pump in an old farmhouse
Schwarme, GermanyThe Schepershus is a classic example of a low-German house from the year 1865 with its own stables and farmyard buildings. The building was purchased in 2018 by the Broscheits as a dream project. The house has around 320 m2 of floorspace and had already been partially renovated. The old windows and doors, for example, had been replaced with new models with double glazing and modern heat transition coefficients. The electrical, water, wastewater and heat distribution systems had also been renovated by the previous owners.
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Requirements:
- Sustainable heat supply
- Comfortable temperatures all year round
- High energy efficiency
Background
BackgroundAfter moving in, the married couple got to work making further changes and modernisations, particularly in the living area. A number of insulation measures were taken on the house’s envelope, such as on the floor ceilings and separating walls. Alongside the couple’s own large living area is another rented apartment, a holiday apartment and a guest room, each with their own bathrooms. The owners spent the previous five years making minor and major improvements alike to the house and farmyard. The most recent of these is the replacement of the old gas heating system with a modern, energy-efficient heat pump.
“We decided to install a heat pump because the issue had been in the news a lot and the price of gas had gone through the roof”, explains Jens Broscheit. “When it came to choosing the heat pump, we did a lot of research before deciding on Mitsubishi Electric. After the specialist partner search function on the website led us directly to a local heat pump supplier, the decision was an easy one.” To make sure that a heat pump was the right solution for the building, the owners gradually lowered the system temperature in the winter and discovered that they could achieve the desired room temperature even with a heating flow temperature of around 50°C.
Project quote
Project quote
“From an installation perspective, the challenge was developing and implementing a modern heating system for this historic building from the 19th century that would deliver a comfortable temperature all year round.”
Which solution was chosen for the farmhouse?
SolutionLocal specialist Schierenbeck Gebäudetechnik e.K. developed an overall heating plan that would deliver a reliable and cost-effective supply of room heating and domestic hot water for the building without the need for burning fossil fuels. Klaus Schierenbeck is a trained installation and heating technician, specialist technical building services planner and energy efficiency expert for residential and non-residential buildings. He developed and implemented the heating concept and the technology involved in the system. “From an installation perspective, the challenge was developing and implementing a modern heating system for this historic building from the 19th century that would deliver a comfortable temperature all year round”, explains Schierenbeck.
Despite the various options available on the market, none of them were as suitable for this building as an air-to-water heat pump system that utilises energy from the outside air. The undisputed advantage of air-to-water heat pumps is their simple and cost-effective way of tapping the heat source. “The decisive factor here was the significantly lower investment costs compared to ground or brine heat pumps. This is where air-to-water heat pumps really come into their own”, explains Schierenbeck. One factor that was particularly important for the client was that an air-to-water heat pump would require the least amount of construction work compared to the alternatives.
The operating principle of heat pumps is as simple as can be: To use the energy contained in the ambient air, the environmental heat absorbed by the heat pumps is transferred to a refrigerant circulating in a closed circuit. The pressure in the refrigerant compressor is increased, the temperature level rises, and a heat exchanger transfers the energy from the refrigerant to the heating circuit water. The system uses two compact type PUD-SHWM140YAAEcodan air-to-water heat pumpsfrom Mitsubishi Electric installed outdoors as a cascade.
Major benefits
BenefitsAdvantageous cascades
Cascading of heat pumps offers numerous benefits over a single heat pump with a correspondingly high output. Cascades have a larger modulation range that ensures smoother operation with no interruptions. They are more efficient because the units work more effectively at partial load (greater energy efficiency). A control with auto-adapt function optimises the operating behaviour and automatically selects the best duty point. In addition, the cascade offers a redundancy function when individual units undergo maintenance, resulting in increased operational reliability. Each of the two Ecodan outdoor units has a rated heat capacity of 14 kW. The heat pumps therefore cover the building’s heating load in monovalent operation, while also providing enough energy for generating domestic hot water.
High energy efficiency with inverter technology
The two outdoor units are located behind one of the stable buildings so they are not visible from the terrace. Each outdoor unit is connected to a hydro box in the technology room. One of the special features of the heating technology used here is the patented Zubadan inverter. It allows the refrigerant mass flow and therefore the compressor speed to be kept constant. To achieve this, a two-part mixture is injected into the compressor head during the compression process. The flash injection circulation of the Zubadan compressor allows the unit to work at a higher speed at low outdoor temperatures, while keeping the amount of refrigerant in the heat pump system constant.
100 per cent capacity even at minus 15°C
These heat pumps can still provide 100 per cent of their heating capacity even at ambient temperatures as low as minus 15°C. At the same time, the lower operating range is extended down to minus 28°C outside temperature, at which the heat pumps can provide a usable temperature for heating operation. This makes it possible to supply the building with heat in monovalent operation (i.e. exclusively via the heat pump function) even at extremely low temperatures. There is no need for an electrical heating element or further heat source.
Storage system for domestic hot water generation
The technology room houses a 1,000-litre combined storage system for generating domestic hot water. This special buffer tank contains a copper heat exchanger in its top section for heating the domestic water. The bottom section houses a storage tank that can hold around 450 litres of heating water for supplying heat to the rooms.
Photovoltaic system included
The buffer tank performs additional tasks in the system. It helps bridge cut-off periods of the energy provider in order to supply sufficient heat at all times, while also providing energy to defrost the outdoor units in winter. An existing photovoltaic system has also been incorporated into the concept. As soon as the solar energy generated on the roof is no longer used for household electricity and the PV solar power storage unit is fully charged, the excess energy is conveyed via an electric heating element to the combined storage tank. The electricity is only fed into the public grid once the specified temperature threshold is met.
The key points
Summary- An old farmhouse and farmyard built around 1865 had already been given a partial energy renovation, but needed a suitable modern heating solution.
- The system uses Ecodan air-to-water heat pumps arranged as a two-unit cascade.
- The cascading ensures energy-efficient operation and increases reliability.
- Each of the two Ecodan outdoor units has a rated heat capacity of 14 kW. The heat pumps therefore cover the building’s heating load in monovalent operation, while also providing enough energy for generating domestic hot water.
- The selected models’ Zubadan inverter technology means these heat pumps can still provide 100 per cent of their heating capacity even at ambient temperatures as low as minus 15°C.
