Tappvattenvärmning med värmepump. Krav och erfarenheter.
Licentiatavhandling, 2012

This licentiate thesis deals with system solutions for heat pump hot water heating in Sweden. Hot water heating requires higher temperatures than space heating and therefore lowers the annual performance of the heat pump system. In existing single family houses, space heating represents the majority of heat pump delivered energy. The demand for space heating decreases in new buildings meanwhile the demand for hot water heating remains, concurrently efficient hot water heating becomes more important. The choice of system solution affects the possibility to save energy. The prerequisites for system development in small houses are examined in this work. It is done partly by a summary of today’s heat pump systems, i.e. the heat pump unit and storage tank, based on different principles for hot water heating. The summary includes pros and cons with these system solutions. The work is also done partly by a survey of demands, requirements, recommendations and testing methods for hot water that can influence the system design. In addition, analysis of data from field measurements on three domestic heat pump systems shows demands, energy relationships and heat pump operation in existing single family houses. Heat pump hot water heating requires some kind of storing of energy since the instantaneous power requirement for hot water heating is huge and the heat pump power is designed for the space heating demand. Typically, tap water is stored in a tank and natural convection is used for the hot water heating. It is important to maintain the temperature stratification in order to maximize the energy extraction from the storage tank. Systems depending on natural convection for water heating, risk unwanted mixing when tapping or recharging occurs. In order to avoid this, the design of the system is important. Storing of water in a closed water loop system decreases the risk of Legionella growth and makes it possible to use a simpler and cheaper tank, compared to fresh water storage as in conventional systems. Hot water heating in an external heat exchanger lowers the risk of mixing in the tank. The heat exchanger dimensions and power can be chosen more freely since it is not limited by the space in the tank as with internal heat exchange. Few measurements on tap water usage are available from single family houses while many exist for multifamily buildings. Standard estimate energy usage for hot water heating is typically between 4000-5000 kWh/year in single family houses. The results from a questionnaire survey made for single family houses with new heat pump installations, shows that the users are well satisfied with the amount and temperature of hot water. Testing methods for hot water heaters tend to move towards detailed tapping patterns that should represent the hot water demand during an actual day instead of a few and large tappings. Even energy efficiency is dealt with in the testing methods by requirements on system efficiency for hot water heaters according to the Ecodesign Directive. Demands on hot water have low impact on the heat pump dimensioning, however tapping patterns can be of importance for the heat pump control system design. iv The operation of three heat pump systems in single family houses is shown through analysis of data from field measurements. Two of the systems are equipped with a desuperheater. The analysis shows annual demand, monthly variations of energy use and detailed heat pump operation during both a summer and winter week. Simplicity and manufacturing costs are prioritized when designing heat pump systems and performance of hot water heating has not been prioritized in existing system solutions. System design can and has been affected by testing methods when connected to a performance requirement. Requirements in the national building code such as limited maximum power for space heating have been important. Potential for system improvements exist with capacity control and better insulation.

system solutions


Heat pump

hot water

Sal EE, Hörsalsvägen 11, plan 6
Opponent: Jan-Erik Nowacki, KTH/Energiteknik


Jessica Benson

Chalmers, Energi och miljö, Installationsteknik


Hållbar utveckling


Building Futures (2010-2018)



Technical report D - Department of Building Technology, Building Services Engineering, Chalmers University of Technology: 2012:03

Sal EE, Hörsalsvägen 11, plan 6

Opponent: Jan-Erik Nowacki, KTH/Energiteknik

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