For so many of us in the lighting industry one of the most confusing aspects of luminaire selection is mixed terminology used by manufacturers when divulging lumen figures. Some quote Luminaire lumens but many quote just lumens or lamp lumens.
So, what’s all the fuss about?
LED luminaire lumens are a measured figure of the amount of light produced by the Led light source once installed inside the luminaire. This takes into account efficiency losses through the diffuser of the luminaire and any other aspect of the luminaire design which may affect its efficiency. Lumens or Lamp lumens are light outputs taken at the led source itself and do not include any losses or inefficiencies of the luminaire.
This fundamental difference is particularly relevant in hazardous area lighting due to the protection concepts employed by manufacturers to achieve a certified or “Zoned” product. Many manufactures use encapsulation or lensing arrangement to achieve the standards. These protection concepts introduce further materials which can reduce the measured light output.
To avoid confusion it is vital to check with the manufacturer if the figures quoted are luminaire lumen figures backed up by photometric tests and reports. This will give you assurance that you are comparing like for like when making specification decisions. Always ask for proof of lumen output claims or even request a specific lighting design from the manufacturer.