Replaceable light sources and Zhaga specifications

Posted on Tuesday October 21 2014, by Tim Whitaker, Zhaga, and Joseph Frederic, UL

In terms of LED light sources and Zhaga specifications, interchangeable and replaceable are two different concepts. Interchangeability applies to all Zhaga-based light sources. In contrast, luminaire makers can choose whether or not their luminaire design allows replacement of the light source, either by the end user or by qualified personnel.

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The Zhaga specifications are designed to enable LED light sources that are interchangeable. In some circumstances, LED luminaires may contain Zhaga-compliant light sources that can be field-replaced, but this is not an intended consequence of Zhaga.

Interchangeable light engines

Zhaga considers that two light engines are "interchangeable" when one light engine can replace the other without any change in the design of the luminaire.

A luminaire manufacturer that builds a Zhaga-compliant luminaire is able to choose from a range of interchangeable, Zhaga-compliant light engines from different suppliers. Or, the manufacturer can produce a luminaire with the same design but different performance by choosing an alternative Zhaga-compliant light engine that has different performance characteristics.

There are many benefits of using interchangeable LED light engines, which are discussed on the Zhaga website – see “Why Use Zhaga Specifications?”.

Interchangeability is relevant both at the factory, when the luminaire is first assembled, and also in the field, when it may be necessary to replace the light engine with another one. But, as discussed below, replacement is not always possible.

Replacement of light engines

In general terms, a “replaceable” light engine is one that can be removed from the luminaire and replaced with another. This may be necessary if the light engine reaches its end-of-life, or if an upgrade, repair or servicing is required.

Zhaga light engines are modular and therefore can easily accommodate replacement. However, a luminaire employing a replaceable Zhaga light source may not be intended or designed to allow field replacement of the light source. Even if replacement is intended, it may be restricted to specific user groups.

There are many factors other than modularity that must be addressed in order for a luminaire to meet regional safety norms and regulations applicable to light-source replacement. These include, but are not limited to; ease of replacement, potential risk to the person performing the replacement, availability of pertinent information about the light source, and system considerations between the luminaire and the light source.

Socketable and non-socketable

Zhaga specifications are written to enable interchangeability, but they do not deliberately set out to enable replaceability. However, in order to help meet the needs of luminaire manufacturers, the Zhaga specifications use designations and parameters that are directly relevant to replaceability.

The luminaire design has a major effect on whether replacement is possible. Some luminaires are “sealed for life”, meaning that the light source can never be replaced.

Zhaga uses the term “socketable” to mean that the light engine or module can be installed or replaced by the end user without the use of tools; this is a key characteristic of user-replaceable light sources. Socketable Zhaga light engines are also provided with electromechanical and thermal codes that can easily convey replaceability information to a non-professional user. These codes are based on the luminaire system, and appear in a complementary fashion on both the luminaire (or socket) and the light engines.

In contrast, “non-socketable” means that the module is intended to be installed or replaced by a professional (where allowed by the luminaire design). This usually implies the use of tools or knowledge of technical ratings. It is assumed that the person performing the replacement is able to discern and handle potentially hazardous situations that may not be evident to a non-professional consumer.

Zhaga interchangeability specifications support both manufacturers who wish to design luminaires with user-replaceable light sources as well as those who wish to restrict light-source replacement to qualified personnel.

Identical performance

It’s important to note that Zhaga certification confirms interchangeability, but does not ensure that two light engines will have identical performance. Many performance characteristics, such as luminous efficacy or lifetime, are not part of the Zhaga Books.

Other characteristics – including luminous flux, CCT, CRI and thermal ratings – are validated during the process of certifying a light engine. However, Zhaga does not set any specific requirements or limits for these parameters. They are measured by Zhaga to verify that the performance quoted by the manufacturer is accurate.

The consequence is that two Zhaga-compliant LED light engines will meet the interface specifications described in a particular Zhaga Book, but otherwise can have different performance characteristics.

However, the availability of dependable data – which has been verified by Zhaga – enables luminaire makers to make meaningful comparisons between different product options.

Further reading

More on this subject can be found in the Replacement section of the "Frequently-Asked Questions" page on our website. 

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