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Department for Business, Energy and Industrial Strategy

Heat Pump Driven Air Curtains

1.1           Scope

Heat Pump Driven Air Curtains are products fitted above a doorway or similar opening that are specifically designed to reduce the infiltration of air from one space to another, and that is heated and/or cooled by a heat pump that transfers heat by means of a refrigeration cycle.

1.2           Definitions

Air curtains are used to reduce losses by disrupting the natural convection between two adjacent spaces that are at differing temperatures, thereby reducing the amount of heating or cooling needed to maintain the temperature of a space. They are typically used in commercial premises for situations where an open door is required to allow uninterrupted access or where traffic through the doorway is so high that the door is open for extended periods.

Heat pump driven air curtains use a heat pump to heat or cool the air expelled by the product. This heat substitutes the need to heat the air with resistive electric heaters or fuel combustion.

The Energy Technology List (ETL) Scheme aims to encourage the purchase of higher efficiency split type heat pump driven air curtains, which have separate heat collection and rejection units for each space known as ‘indoor’ and ‘outdoor’ units. The ‘indoor’ and ‘outdoor’ units are specifically designed to be connected together during installation by refrigerant pipework to form a single functional unit.

The sub-technology described within this Specification covers:

1.     Single-split Heat Pump Driven Air Curtains, that consist of one ‘outdoor’ heat pump unit and one air curtain unit.

Heat pump driven air curtain units for multi-split and VRF heat pumps, that consist of one air curtain unit that is specifically designed to replace one or more ‘indoor’ heat pump units are covered by the Air to Air Heat Pumps, Split, Multi-Split and VRF sub-technology.

1.3           Requirements

1.3.1       Eligibility requirements

To be eligible for inclusion on the ETL, products shall meet the requirements as set out below.

To be eligible, products shall:

  • Include an air curtain unit or package that:
    • Is specifically designed to be fitted above a doorway or similar opening.
    • Is specifically designed to use a heat pump to heat and/or cool the air curtain expelled by it, and to use electrical air heaters (where fitted) only during defrosting or heat pump failure.
    • Has been rated in terms of air curtain airflow rate, outlet air velocity uniformity and air curtain velocity projection in accordance with the procedures in BS ISO 27327-1:2009.
  • Be able to automatically modulate in response to changes in air inlet temperature and/or space temperature(s), the amount of heating and/or cooling applied to the air curtain between 40% and 100% of its nominal rated heating/cooling capacity output.
  • Be designed for, and include fittings for, permanent installation.
  • Have an appropriate Conformity Assessment mark.

In addition, single split heat pump driven air curtain products shall:

  • Consist of one air curtain unit (or package) and one outdoor heat pump unit that are:
    • Factory–built sub-assemblies.
    • Supplied as a matched set of units.
    • Designed to be connected together during installation.
  • Incorporate an electrically driven refrigeration system that uses a refrigerant which has a Global Warming Potential (GWP) ≤ 750.

1.3.2       Performance requirements

Eligible products shall meet the performance criteria set out in Table 1.1 below for:

  • Coefficient of Performance (COP), across the range of connected capacities, including at 100% (full) load, in heating mode, where the product is designed to heat the expelled air.
  • Energy Efficiency Ratio (EER) across the range of connected capacities, including at 100% (full) load in cooling mode, where the product is designed to cool the expelled air.
  • Outlet air velocity uniformity (uACU), as defined in Section 5.4.4 of BS ISO 27327-1: 2009, over the range of doorway/opening heights that they are designed to be fitted above.

Table 1.1    Performance requirements for heat pump driven air curtains


Product Category

Heating mode (COP)

Cooling mode (EER)

Outlet air velocity uniformity (uACU)


Single-split heat pump driven air curtains



≥ 70%

"≥" means "greater than or equal to"

1.3.3    Information requirements

Supplier shall report the following parameters for each model, which will be published on the ETL Product Search:

  • Whether the model has ‘smart features’. Specifically, this includes the capability to provide information on whether the products are ‘smart ready’ without the replacement or addition of any hardware, which includes the following one or more options:
    1. Demand Side Response Ready
    2. Date Collection Ready, which includes:
      • Storing data on the heat pump or a remote device.
      • The ability to store data for each calendar year as a value per day, per month or per year.
      • The following real time value parameters: electricity energy consumption (kWh); heat delivered (kWh); energy efficiency performance; operating times (days, hrs); number of on/off cycles.
  • The SCOP and SEER for products with a duty greater than 12 kW with an efficiency performance presented in: COP and EER.

1.4           Measurement and Calculations

1.4.1       Energy efficiency metrics

Coefficient of Performance (COP) - ratio of the heating capacity to the effective power input of the unit (as defined by BS EN 14511:2022).

Energy Efficiency Ratio (EER) - ratio of the total cooling capacity to the effective power input of the unit (as defined by BS EN 14511:2022).

Outlet air velocity uniformity (uACU) - a percentage calculated from the average air curtain core velocity and velocity’s standard deviation, as defined by BS EN 27327-1:2009

Seasonal Coefficient Of Performance (SCOP) – overall coefficient of performance of a heat pump using electricity, representative of the heating season, calculated as the reference annual heating demand divided by annual energy consumption for heating (as defined by Ecodesign Commission Regulation (EU) 2016/2281).

Seasonal Energy Efficiency Ratio (SEER) – overall energy efficiency ratio of a heat pump working in reverse mode for a representative cooling season, calculated as the reference annual cooling demand divided by the annual energy consumption for cooling (as defined by Ecodesign Commission Regulation (EU) 2016/2281).

1.4.2       Test Requirements

No additional testing requirements beyond the measurement standard below.

1.4.3       Measurement standards

All products shall be tested in accordance with the procedures in BS EN 14511:2022 using the standard rating conditions as set out in the Table 1.2 below.

Table 1.2    Test conditions for heat pump driven air curtains ​​​


Product Category

Heating mode (COP)

Cooling mode (EER)


Single-split heat pump driven air curtains

Air source

BS EN 14511:2022

Table 4 Standard rating conditions, Outdoor air/recycled air.

BS EN 14511:2022

Table 5 Standard rating conditions: Comfort (outdoor air/recycled air)

Please note that performance data obtained in accordance with the procedures and conditions laid down in BS EN 14511: 2011, BS EN 14511: 2013 and BS EN 14511: 2018 will be accepted as an alternative to testing in accordance with BS EN 14511: 2022 until further notice. Outlet air velocity uniformity shall be tested in accordance with BS EN 27327-1: 2009.

1.4.4       Rounding 

For the avoidance of doubt test data for COP and EER should be presented to 2 decimal places. As an example, a single split heat pump driven air curtain with a heating mode COP of 3.094 would be deemed to be a fail.

1.5           Verification for ETL Listing

There are five main ways that applicants can demonstrate their product’s performance:

  • In-house testing – Self-certified
  • In-house testing – Self-tested and verified or cross-checked by an independent body
  • Witnessed testing
  • Independent testing
  • Representative testing (see clause 1.5.1)

Further information regarding the first three routes can be found in the ETL Testing Framework.

1.5.1       Representative Testing

Where applications are being made for two or more products that are variants of the same basic design, test data may be submitted for a single ‘representative model’, provided that all products:

  • Use the same model of outdoor unit.
  • Use the same refrigerant as the representative model.
  • Provide the same air curtain core velocity range allowing for same installation height.

The representative model may be selected by dividing the range of products into groups of models with similar design characteristics. The performance of each model shall be predicted using a validated mathematical model. At least one model in each group shall be tested for validation purposes. A report documenting the performed model calculations, showing all significant calculation steps, shall be submitted with the application.

It should be noted that:

  • If a manufacturer voluntarily removes the representative model from the ETL then other products linked with that representative model may or may not be permitted to remain on the ETL.
  • If any product submitted under these representative model rules is later found not to meet the performance criteria when independently tested, then all products based on the same representative model will be removed from the ETL.

1.6           Conformity testing

Products listed on the ETL may be subject to the scheme’s conformity testing programme in order to ensure listed models continue to meet the ETL requirements.

1.7           Review

1.7.1       Indicative review date

The next technical review is scheduled for 2025-26.

1.7.2       Illustrative future direction of the requirements 

Future changes to the Specification may include:

  • Increasing the performance thresholds for COP and EER
  • Increase the outlet air velocity uniformity performance threshold.
  • Updates to product eligibility and functionality requirements as per market demand any UK or EU regulatory changes. 
  • The possibility of ‘smart features’ becoming an eligibility requirement for listed heat pump driven air curtains. 
  • Update the product eligibility requirements to encompass embodied lifetime carbon of heat pumps. Introducing a maximum value (measured in tonnes/ CO2) for the lifetime carbon of a heat pump.