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Test Procedures for Heat Pump Water Heaters

Test procedures are the basis for quality labels, calculation models and therewith an important element in governmental policy instruments. However world-wide there is a disturbing landscape with a great number of test methods for heat pump water heaters in use in different regions of the world, with major differences between them. As a result, manufacturers have to undertake a different set of tests to be able to sell their products on the worldwide market. Harmonisation of test procedures is urgently needed.

Worldwide test standards are strongly related to quality labels which are not harmonized.

There is no single «best» test method, which could be adopted for global use – all have their advantages and disadvantages.’

In an analyses Presented by Cordin Arpagaus (OST) at the Workshop in Seoul 2019, indicated the differences in standards, main points besides the climatic conditions in the different regions.

In a follow up of the SEAD Report ‘Heat Pump Water Heaters: Potential for Harmonization of International Test Standards’, the ISO Working Group 12 on Heat pump water heaters of ISO/TC 86/SC 6/WG 12 on HPWHs has developed a harmonisation framework, for drafting  a test procedure now available as standard  ISO 19967-1:2019.

What are the next steps towards global harmonization?

  • Challenge 1: How to handle innovative solutions / range of products, e.g. multi-function heat pumps, hybrid heat pumps, fresh water heat pump systems, booster heat pumps, combination of solar and heat pumps, extended smart storage systems, larger than 50/80 kW systems, cascade heat pumps, etc.
  • Challenge 2: Harmonize the nomenclature of systems
  • Challenge 3: Have a clear definition of performance
  • Challenge 4: Set guidelines for harmonization:
    • Scope of testing procedure
    • Major objectives of the testing procedures (What parameters are to be established ?)
    • Identification of similarities among different procedures
    • Level of complexity/duration of the test procedure
    • Scalability of the procedure to smaller vs. larger storage tanks
    • Applicability of various technologies (e.g. electric, gas fired, HP, tankless etc.)

Quality Labels

Standards are used for various purposes at legislative level and for other purposes:

  • Energy performance labelling, like European ECO label, TOP Runner in Japan, China Energy Label (CEL), Energy Star and Energy Guide labels in North America
  • In practice, standards are also used for design purposes used in a number of (often commercial) calculation models.
  • Governmental information models, like the SAP (add abbreviation as footnote) and RdSAP models in the UK with which the EPC for the building is calculated

Traditionally, energy efficiency standards and labels have set performance requirements for water heaters by type (e.g., storage electric water heater, gas instantaneous water heater, etc.), thus inhibiting the comparison across water heater technology classes.

Test Centres

Worldwide certified Test Centres do measurements on Heat Pump Water Heaters according to the standards. These Test Centres are certified in line with ISO/IEC 17025, which enables laboratories to demonstrate that they operate competently and generate valid results, thereby promoting confidence in their work both nationally and around the world.

In Europe the European Heat Pump Association publishes and updates a list of testcentres in Europe.

Test Centre at OST in Buchs (Switzerland)

Work to be done

Many of the test procedures focus mainly on air source Heat Pump Water Heaters (often mon-bloc), being the main stream, while there is a large number of alternative and often innovative new heat pump technologies supplying domestic/sanitary hot water. For these there are no standardized test procedures available or if available not acknowledged at international level.

Discussion points on test procedures:

  • How to rate air source DHW HP’s in different climatic conditions, when the HP’s are tested at only one temperature? The Northwest Energy Efficiency Alliance published in 2020 the report Load-based and Climate-Specific Testing and Rating Procedures for Heat Pumps and Air Conditioners.
  • Smart control also effects manufacturers to let air source systems run during the day, when higher temperatures are available
  • In test procedures different combinations of heat pump and storage tank (size) are considered as different heat pumps to be tested individually. Why not separate these and combine through a calculation module?
  • Should the temperature of the storage tank be fixed at a certain level in agreement with the demands for legionella?

Annex Report on Test Procedures

The Annex has in its collaboration analysed the work done on Test Procedures for Heat Pump Water Heaters. The Final Report on this is available and can be downloaded.