Performance map instead of a single point: what EN 14511 and EN 14825 demand of the test bench

A heat pump does not have a capacity, it has a performance map. What stands on the rating plate is one point from it — at a particular source temperature, a particular flow temperature and a particular spread. Anyone who leaves these three figures out has said nothing.

The European standards lay this down very precisely: EN 14511 the test conditions and test methods, EN 14825 the part-load points and the formation of the seasonal figures. This paper works out which requirements for the test bench follow from them — and why the toughest figure in the whole family of standards is not found at the capacity, but at the temperature difference.

01 · The family of standards

EN 14511 carries the common main title „Luftkonditionierer, Flüssigkeitskühlsätze und Wärmepumpen für die Raumbeheizung und -kühlung und Prozesskühler mit elektrisch angetriebenen Verdichtern“ and is divided into four parts, all in the 2022 edition and as the German version of 2023 respectively:^{[1] [2] [3] [4]}

To these are added EN 14825 for seasonal efficiency^{[5] [6]}, EN 16147 for domestic hot water heating, EN 12102-1 for noise measurement and EN 15879-1 for direct exchange systems. The Heat Pump KEYMARK certification scheme cites all of them as its normative basis and puts one principle first that is often missing from invitations to tender: only valid editions of a standard apply.^[7]

02 · Test conditions and rating points

EN 14511-2 defines four temperature applications for the sink, each by way of the outlet temperature:^[8]

On the source side, for air the standard condition given is 7 °C dry bulb at 6 °C wet bulb, together with the application conditions 2/1 °C, −7/−8 °C, −15 °C and 12/11 °C; for water and brine, inlet 10 °C and outlet 7 °C apply.^[8] The widespread shorthand notation is an industry convention and not a provision of the standard — it is documented, for instance, in the KEYMARK annex, which names the test points as A7/W35, A20/W35, B0/W35 and W10/W35 to EN 14511-2 and E4/W35 to EN 15879-1.^[9] The first letter is the source, the number the source temperature, the W figure the water outlet temperature.

03 · What is included in the power input

This is the most common source of COP figures that cannot be compared. EN 14511-3 requires the effective power input to contain the correction for fans and pumps — regardless of whether they are integrated in the unit or not.^[10]

The reasoning behind it: what counts is not the hydraulic power of the test bench but the equivalent electrical effort for the pressure drop on the unit side. The effect is considerable — one technical account puts the influence of the correction on the COP at up to 0.3.^[11] Defrosting likewise enters into the COP: the defrost heat is taken from the heating circuit, and the energy needed for it is accounted for when the COP is determined; depending on the quality of the defrost algorithm this costs 0.3 to 1.0 COP points.^[11]

For ducted indoor units, Part 3 specifies minimum values of external static pressure, graded by rated capacity — from 25 Pa up to 8 kW to 175 Pa from 147 kW. If the actual static pressure exceeds twice the minimum value, the fan speed is to be adjusted accordingly.^[10]

04 · Tolerances and measurement uncertainties

The standard separates cleanly between two things that often blur in everyday usage: the permissible deviation of the set test condition during the measurement, and the permissible measurement uncertainty of the measuring chain.

For determining the capacity, EN 14511-3 carries three normative methods: the calorimeter room method in Annex A, the indoor air enthalpy method in Annex B and the liquid enthalpy method in Annex D; air flow rate measurement is governed by the normative Annex I, the pump efficiencies by the normative Annex F.^[10]

05 · Part load, bins and the SCOP

EN 14825 determines the seasonal figures SEER, SCOP and the associated efficiency data; the methods may be based on measured or on calculated values.^[6] Three climate zones are defined, each with 8760 hours:^[12]

Besides the four points A to D, EN 14825 has further points up to G for heating; to these are added the bivalence temperature, the operation limit temperature and, optionally, a point at −15 °C.^[14] For the reference climate the Ecodesign Regulation sets the design temperature at −10 °C, the bivalence temperature at no more than +2 °C and the operation limit temperature at −7 °C; the European reference heating season comprises 4910 hours a year.^[15]

A methodological criticism that matters for test bench engineering is aptly put by one technical publication: at every test point all three operating parameters change at the same time — source temperature, sink temperature and heat output.^[14] A clean performance map therefore cannot be separated out from EN 14825 points.

On the reference to the European regulations: Ecodesign Regulation (EU) No 813/2013 defines the seasonal space heating energy efficiency and the conversion coefficient 2.5^[15], the energy labelling Regulation (EU) No 811/2013 the efficiency classes — for low-temperature heat pumps A+++ starts at 175 %.^[16] The market surveillance tolerance is 8 % for seasonal efficiency and 2 dB for the sound power level.^[15]

06 · Defrosting: the transient part

This is where the standard makes the highest demands on data acquisition — and where improvised test benches fail.

Steady state counts as reached when all measured quantities remain within the permissible deviations for at least 30 minutes without any change of the set points. The measurement period that follows is at least 35 minutes, with a complete record at least every 30 seconds.^[10] These are two separate requirements, not overlapping ones.

For transient operation with defrosting the standard defines two types of interval: an interval H is a heating period excluding the first ten minutes after the end of defrosting; an interval D consists of a defrost cycle plus the first ten minutes of heating operation after it.^[10] The sampling rates differ accordingly:

One requirement for the test chamber that follows from this and is seldom thought of: for the acoustic test the EHPA regulation prescribes that, for units with defrost cycles, the humidity at the inlet is controlled such that during the measurement no defrosting occurs.^[13] The chamber must therefore be able not only to humidify, but also to dehumidify in a controlled way.

07 · What that means for the test bench

A requirement profile follows from the requirements quoted. It is our derivation, not that of the standards.

For flow rate measurement on the air side, the relevant method standards are the ISO 5167 series for differential pressure devices — in particular Part 3 for nozzles and Venturi nozzles^{[18] [19]} — and ISO 5801 for fan test benches.^[20] On the American side the counterpart is ANSI/AMCA 210 or ASHRAE 51 in the 2025 edition.^[21]

In addition, a requirement from ISO 5167-1 that is relevant for speed-controlled fans: the standard applies to subsonic single-phase flow and expressly excludes pulsating flow.^[18]

Who tests and who certifies

There are two established routes to certification. The Heat Pump KEYMARK covers heat pump space heaters, combination heaters and water heaters up to 400 kW and works with tolerances on declared values of −8 % for seasonal efficiency and for rated capacity, and +2 dB(A) for sound power — the same values as the market surveillance tolerances of the Ecodesign Regulation.^[7] The EHPA quality label works with its own testing regulations for each type of unit and makes the calorimeter room method mandatory for air/air units.^{[13] [22]}

08 · The change of refrigerant

The F-gas Regulation (EU) 2024/573 of 2024-02-07, in force since 2024-03-11^[23], prohibits the placing on the market of units with fluorinated refrigerants above certain global warming potentials, graded by type of unit and capacity. For heat pump development these dates are above all the decisive ones:^{[24] [25]}

What R290 means for the test bench

Propane is classified in safety group A3 to ISO 817, that is, highly flammable, has a global warming potential of 0.02 and an auto-ignition temperature of 470 °C; the maximum surface temperature permitted to EN 378-2 is 370 °C. As a non-F-gas it is exempt from the leak checking obligation of the F-gas Regulation.^[26]

For the installation room, EN 378-3 is the governing document, supplemented by the rules on explosion protection. One technical account names the following equipment:^[27]

For the hazardous area classification, EN 60079-10-1 and EN 1127-1 are the relevant documents; for the qualification of personnel, EN 378-4 and ISO 22712.^[28] A guide to outdoor installation lists expressly the ignition sources to be avoided within the protected area — down to electronic devices such as mobile telephones and notebooks — and requires that during intended operation no ignition sources are present there, neither permanently nor briefly.^[29]

What that means for the design of the test bench

A test bench for propane-operated heat pumps is not a climatic cabinet with additional equipment. It is a plant with a hazardous area concept, gas detection in several stages, explosion-protected ventilation, extraction close to the floor and a safety chain that in the event of a fault first ventilates and then isolates. These points belong in the design and not in commissioning — they determine the installation, the room height and the cable routing.

09 · Sources

The EU regulations and the testing regulations of the certification schemes are freely available and often more productive for the design of a test bench than the texts of the standards themselves — they name the test points explicitly.