What Is an LED Capsule Bulb? G9 and G4 Types, Selection Criteria
An LED capsule bulb is a small LED light source for two-pin G9 or G4 holders that replaces halogen capsules in small luminaires.
An LED capsule bulb is a small LED light source that fits a two-pin G9 or G4 holder. It replaces halogen capsule lamps in chandeliers, wall lights and small decorative luminaires with little room for the lamp. A G9 capsule connects directly to the mains; a G4 capsule usually runs on 12 V and needs a transformer or power supply.
G9 and G4 capsules compared
| Feature | G9 | G4 |
|---|---|---|
| Pins | Two looped pins, 9 mm apart | Two thin straight pins, 4 mm apart |
| Voltage in the catalogue | 220 V, directly on the mains | 12 V, via a transformer or power supply |
| Typical use | Chandeliers, wall lights, crystal luminaires | Small spotlights, 12 V chandeliers and display luminaires |
Because the pin layouts differ, G9 and G4 lamps cannot replace each other.
Selection criteria
- Holder and voltage: First check the holder and voltage of the old lamp in the luminaire. Do not connect a 12 V G4 capsule to the mains.
- Body size: An LED capsule is often longer and thicker than a halogen capsule with the same cap. Check that it fits inside the luminaire's glass or bowl.
- Transformer compatibility (G4): Electronic transformers made for halogen lamps may not work, or may flicker, with a low-wattage LED load. Use an LED-compatible 12 V power supply and check the label for whether the lamp needs AC or DC.
- Light colour: The capsules in the catalogue come in 3200 K (warm white) or 6400 K (cool white). Use one colour in the same luminaire.
- Dimmability: On a dimmer circuit, fit only capsules stated as dimmable.
Common mistakes
- Fitting an LED without changing the halogen transformer: The G4 LED capsule does not light or flickers.
- Forcing the lamp into the luminaire: The capsule or the luminaire glass is put under mechanical stress and can break; choose a capsule of the size the luminaire allows.
- Choosing by wattage: Compare LED capsules by lumens; the same wattage can give different light output.
Related standards
- IEC 60061-1: Dimensions and interchangeability of lamp caps, including G9 and G4; lampholders are in IEC 60061-2.
- IEC 62560: Safety requirements for self-ballasted LED lamps on mains above 50 V; 12 V G4 capsules are outside its scope.
In the Welibaba catalogue
There are 5 active Cata products in the LED Capsule Bulbs category, all sold by the piece:
- G9, 220 V: CT-4221 and CT-4249 (3 W), CT-4222 and CT-4248 (4 W); CT-4221 and CT-4222 use COB LEDs
- G4, 12 V: CT-4252 (4 W)
Candle-shaped E14 lamps are in LED Candle Bulbs, E27 lamps in LED Bulbs.
Frequently asked questions
Can an LED G9 replace a halogen G9?
Yes, the cap and voltage are the same. The LED body may be longer, so check that it fits inside the luminaire's glass.
Which transformer does a 12 V G4 LED capsule need?
An LED-compatible 12 V power supply. An electronic transformer made for halogen lamps may not work with a low LED load; check the label for whether the lamp needs AC or DC.
What is the difference between G9 and G4?
G9 has looped pins 9 mm apart and runs on the mains. G4 has straight pins 4 mm apart; the model in the catalogue runs on 12 V.
Should I choose 3200 K or 6400 K?
3200 K warm white is common in homes, chandeliers and wall lights. 6400 K cool white is more for display and work areas.