Lamp Holder Explained: Socket Types, Designations & Selection
What Is a Lamp Holder?
A lamp holder – also known as a socket or lamp socket – is the fitting in a luminaire into which the light source is inserted. It provides both the mechanical support and the electrical contact between the luminaire and the light source. The lamp holder determines which light sources are compatible with a luminaire, making it a decisive criterion when selecting replacement lamps.
How Are Lamp Holders Designated?
The designation system for lamp holders and their corresponding lamp bases follows a standardised scheme:
The first letter describes the base type:
- E = Edison screw thread
- G = Pin or plug-in base
- GU = Pin base with twist-lock mechanism
- R = Base with recessed contact
- B = Bayonet base
The number that follows indicates the relevant dimension in millimetres – usually the diameter of the screw thread or the distance between the pins.
The most common lamp holders at a glance
- E27: The standard holder for domestic use – recognisable by its large screw thread (27 mm diameter). Compatible with classic incandescent lamp shapes, LED filament lamps and many retrofit light sources.
- E14: The small screw holder (14 mm diameter), frequently found in candelabras, decorative luminaires and wall luminaires. Typical lamp shapes include candle, drop and globe.
- GU10: Plug-in base with a twist-lock mechanism and a pin spacing of 10 mm. The standard holder for reflector lamps and LED spots that operate directly at 230 V. Widely used in recessed luminaires, surface-mounted spotlights and track systems.
- GU5.3 (MR16): Plug-in base with a pin spacing of 5.3 mm. Operates at 12 V low voltage and therefore requires a transformer or LED driver. Common in recessed spotlights and accent lighting.
- G9: Compact plug-in base with two wire loops spaced 9 mm apart. Typical for small, compact luminaires and design luminaires where space is limited. Operates at 230 V.
- G4 / GU4: Very small pin bases with a 4 mm pin spacing for low-voltage lamps (12 V). Found primarily in furniture-recessed luminaires, cooker hoods and decorative luminaires.
- R7s: Double-ended linear base for halogen linear lamps and their LED replacements. Typical for uplighters and work floodlights.
Frequently Asked Questions (FAQ)
How do I find the right lamp holder for my luminaire?
The required lamp holder is specified in the technical data of the luminaire – on the type plate, in the operating instructions or in the product details in the shop. Alternatively, you can check the existing light source: the base type is usually printed on the lamp itself.
Can I use an LED light source in any lamp holder?
Suitable LED light sources (retrofit LEDs) are available for all common lamp holders. Make sure that the base type, voltage (230 V or 12 V) and dimensions are compatible with the luminaire body.
What do E27 and E14 mean?
E stands for Edison screw thread – named after Thomas Edison. The number indicates the thread diameter in millimetres: E27 has a 27 mm diameter, E14 has a 14 mm diameter.
In Summary:
The lamp holder is the link between luminaire and light source. To find the right light source, you need to know the base type of your luminaire. At Leuchtenland.com you will find the lamp holder specification in the product details for every luminaire – and the matching light source directly in the shop.