⚠️ Warning – Fluorescent Ballast Installation
Australian Compliance Notice:
Important: In Australia, installation or replacement of fluorescent ballasts connected to fixed wiring should only be carried out by a licensed electrician in accordance with the current AS/NZS 3000 Wiring Rules and all applicable state or territory electrical safety regulations.
This blog is for sharing tips only. Do not do it if you are NOT qualified.
If you're replacing or installing a 7 terminal dimmable fluorescent ballast, it's important to wire it correctly. Incorrect wiring can damage the ballast, reduce lamp life, or create an electrical hazard.
Thanks to James (from NLS Lighting) and Georgie (from Mel). They provide so much patients and well knowledge to work it out. I hope i could share some tips for this case.
The case is, Georgie has 2x36W fluorescent lamp batten, and want to make light dimmable. The job is, change original 2x36W ballast to 2x36W dimmable ballast. Also change compatible dimming controller. This job use "Osram Quicktronic De Luxe HF Dimmable Ballast 2X36W" which we provided.
What Is a 7 Terminal Dimmable Ballast?
A 7 terminal dimmable ballast is commonly used with fluorescent lighting systems that support brightness adjustment using a 1-10V analogue dimming control.
Unlike a standard ballast, a dimmable ballast includes additional low-voltage control terminals that allow compatible dimmers or building management systems to adjust light output.
Typical 7 Terminal Layout
Although terminal numbers vary by manufacturer, most 7-terminal dimmable ballasts include:
| Terminal | Function |
|---|---|
| L | Active (Live) 240V AC |
| N | Neutral |
| Lamp Output 1 | Connects to fluorescent lamp |
| Lamp Output 2 | Connects to fluorescent lamp |
| Lamp Output 3 | Connects to fluorescent lamp |
| DIM + | Positive 1-10V dimming control |
| DIM – | Negative 1-10V dimming control |
Some manufacturers label the dimming terminals as:
- DA+
- DA-
- 1-10V+
- 1-10V-
- Control +
- Control –
Always check the wiring diagram printed on the ballast before connecting power.
Typical Wiring Diagram
240V Supply Active (L) -------------------- L Neutral (N) ------------------- N Lamp Terminal ----------------- Lamp Pin Lamp Terminal ----------------- Lamp Pin Lamp Terminal ----------------- Lamp Pin Dimmer (+) -------------------- DIM + Dimmer (-) -------------------- DIM -
*Shows how to wire on right side. Draw by James from NLS Lighting.*
Understanding the Dimming Terminals
The final two terminals are used for the 1-10V control signal, not mains voltage.
Typical operation:
- 10V = Full brightness
- 1V = Minimum brightness
- Open circuit = Usually full brightness (manufacturer dependent)
Never connect 240V mains power to the dimming terminals.
Doing so will permanently damage the ballast.
A standard household trailing-edge or leading-edge wall dimmer cannot directly dim most fluorescent ballasts.
Most dimmable fluorescent ballasts require:
- 1-10V analogue dimmer
- DALI controller (if DALI model)
- Digital lighting control system
Please see the video below, shows how 36W warm white fluorescent tube dim on dimmable ballast.
