The Ulbricht sphere: Exact detection of the radiant power of radiant heaters

Regulatory requirements for open-plan buildings

Since 1 January 2018, luminous and dark radiant heaters are subject to the technical requirements of the Ecodesign Regulation (EU) 2015/1188.

The regulation implementing the ErP Directive (EU) 2009/125/EG limits the permissible NOx emissions – nitrogen oxides that are produced during operation – and requires a minimum value for seasonal energy efficiency.

The ErP Directive combines certain groups of products into so-called LOTs. Heaters are described in lots 1, 2, 15, 20 and 21. Combining them into individual lots makes it possible to compare the efficiency and emissions (exhaust gas, noise) of the heating systems.

  • Lot 1: Boilers and combiboilers
  • Lot 2: Water heaters
  • Lot 15: Solid fuel boilers
  • Lot 20: Local space heaters
  • Lot 21: Central heating products using hot air to distribute heat

A labelling requirement excludes gas-fired radiant heaters used in commercial and industrial buildings under this Regulation.

For gas-powered luminous and dark radiant heaters used in commercial buildings, the previously valid standards EN 419-2 and EN 416-2 provided two physically different measurement methods (so-called "Method A" and "Method B") for determining the radiation factor (radiated portion of the power output).

The description of the measuring methods was incomplete or imprecise according to today's state of the art. As a result, uncertainties in the determination of the radiation factor of these gas appliances have occurred in the past.


Section Gas - Manager
Dipl.-Ing. Harald Petermann

+49 221-37668-57

The development of the Ulbricht sphere enables exact measurement of the radiant power

In a current scientific study of the National Metrology Institute of Germany (Physikalisch-Technische Bundesanstalt, PTB) in cooperation with the European Association of Luminous Radiant Gas Heater Manufacturers e.V. (ELVHIS), the following results have been obtained, an Ulbricht integrating sphere has been developed as a central element of the measurement setup. This is a further development of the previous radiometric measurement method B, which reproducibly enables the physically correct and exact measurement of the radiant power of the radiation heaters mentioned. 

The findings of the PTB study (PTB report from 13 February 2017: short summary of the report for figawa members) on the specification, the manufacturing process and the suitability test of the Ulbricht integrating sphere defined in this way were adopted in the three new draft standards prepared by the CEN TC 180:

  • prEN 416:2017 Gas-fired overhead radiant tube heaters and radiant tube heater systems for non-domestic use - Safety and energy efficiency
  • prEN 419:2017 Gas-fired overhead luminous heaters - Safety and energy efficiency
  • prEN 17175:2017 Gas-fired overhead radiant strip heatersand multi-burner continuous radiant tube heater systems for non-domestic use – Safety and energy efficiency

The measurement method thus described is permitted in the new drafts of these standards as the only method for determining the radiation factor of the types of equipment mentioned.

figawa contributed these findings in the work of the DIN. As a result, DIN-NA 032-03-01 AA recommended that the measuring methods described in the new draft standards be used immediately for type examinations and for market surveillance tests of the relevant device types.

Research project of ELVHIS e.V.