Choice of transformer for CCT lights (spots, panels and strip lighting)
How does CCT technology work?
CCT (Correlated Color Temperature) LED technology allows the colour temperature of white light to be adjusted from warm (e.g. 2700K) to cool (e.g. 6500K). This is achieved by two LED circuits: warm and cool
Only one LED circuit is active at a time, or actually a CCT LED circuit draws power from only one circuit.
This means that even if the product says 9W CCT, for example, it actually has 2 x 9W circuits, and the CCT controls balance the power to 9W. Therefore, the power consumption is at most 9W - not 18W.
This applies to all CCT products: spots, panels and strip lighting.
Unfortunately, it is misleading that the product names for strip lighting indicate the sum of the two circuits (e.g. 14.4W/m), while spots and panels are indicated at the actual consumption (e.g. 9W).
When choosing a transformer, the actual consumption should always be used.
How to choose the right transformer?
- Calculate the total power (W) of all luminaires
- Add a safety margin of approx. 15
- Choose a transformer according to the control mode (RF, Zigbee, DALI)
Indicative power table for CCT spots and panels
| Luminaire | Power (W) |
|---|---|
| Spot CCT | 9 W |
| Spot CCT | 12 W |
| Panel CCT | 6 W |
| Panel CCT | 12 W |
| Panel CCT | 15 W |
| Panel CCT | 18 W |
| Panel CCT | 30 W |
| Panel CCT | 60 W |
Transformer tables for spots and panels
9W CCT spot
| Quantity | Power | Recommended transformer |
|---|---|---|
| 2 | 18 W | 30 W |
| 3-4 | 36 W | 50 W |
| 5-6 | 54 W | 75 W |
| 7-8 | 72 W | 100 W |
| 9-12 | 108 W | 150 W |
| 13-16 | 144 W | 200 W |
Examples of panel power calculations
| Panels (W) | Quantity | Total power | Transformer |
|---|---|---|---|
| 6 W | 5 | 30 W | 50 W |
| 15 W | 5 | 75 W | 100 W |
| 30 W | 3 | 90 W | 100 W |
| 60 W | 2 | 120 W | 200 W |
CCT LED strips and actual power
LED strip lights often indicate the nominal power as the sum of two circuits, e.g. "14.4W/m" means 2 x 7.2W/m. But since only one circuit is lit at a time, the actual power consumption is at most half the nominal power.
Examples of strip consumption
- "7,2W/m" actual power consumption of a strip ≈ 5,5W/m
- '30W/m' actual tape power ≈ 20W/m
CCT led strip lighting power consumption for transformer calculation
| Tape | SKU | WW (W) | CW (W) | Req. (W) | |
|---|---|---|---|---|---|
| SOLO TUNNELMA, CCT, 24V, 3.6W/m, IP65, CRI95 | STRIP36-24V-IP65-CCT-COB | 2,2 | 2,2 | 2,9 | |
| SOLO TUNNELMA, CCT, 24V, 7.2W/m, IP65, CRI95 | STRIP72-24V-IP65-CCT-COB | 4,1 | 4,1 | 5,5 | |
| SOLO TUNNELMA, CCT, 24V, 14.4W/m, IP20, CRI93 | STRIP144-24V-IP20-CCT-COB | 7,7 | 7,7 | 10,3 | |
| SOLO TUNNELMA, CCT, 24V, 30W/m, IP20, CRI92 | STRIP30-24V-IP20-CCT-COB | 15,6 | 15,6 | 20,8 | |
| NEON, CCT, 24V, 14.4W/m, IP65, CRI95 | STRIP144-24V-IP65-CCT-NEON | 7,9 | 7,9 | 10,6 | |
| HELMI TUNNELMA, CCT, 24V, 7.2W/m, IP65, CRI94 | STRIP72-24V-IP65-CCT-SMD | 3,4 | 3,4 | 4,5 | |
| HELMI TUNNELMA, CCT, 24V, 14.4W/m, IP20, CRI94 | STRIP144-24V-IP20-CCT-SMD | 6,0 | 6,0 | 8,0 | |
| HELMI TUNNELMA, CCT, 24V, 22W/m, IP20, CRI93 | STRIP22-24V-IP20-CCT-SMD | 11,8 | 11,8 | 15,7 | |
Power consumption of RGBW and RGB+CCT LED strip lighting in transformer calculations
| Tape | SKU | WW (W) | CW (W) | R (W) | B (W) | G (W) | Req. (W) |
|---|---|---|---|---|---|---|---|
| HELMI CHAMELEONTS, RGB+W, 24V, 14.4W/m. IP65, CRI85 | STRIP144-24V-IP65-RGBW-SMD | 0,0 | 7,8 | 7,8 | 7,8 | 7,8 | 10,4 |
| CHAMELEONTS, RGB+W, 24V, 15W/m, IP65, CRI90 | STRIP15-24V-IP65-RGBW-COB | 0,0 | 7,8 | 7,8 | 7,8 | 7,8 | 10,4 |
| SOLO SPEKTRI, RGB+CCT, 24V, 19W/m, IP20, CRI90 | STRIP19-24V-IP20-RGBCCT-COB | 2,6 | 2,6 | 2,6 | 2,6 | 2,6 | 7,1 |
| HELMI SPEKTRI, RGB+CCT, 24V, 20W/m, IP20, CRI94 | STRIP20-24V-IP20-RGBCCT-SMD | 2,4 | 2,4 | 2,4 | 2,4 | 2,4 | 6,4 |
Example calculation
SOLO 30W CCT strip 4m:
4 x 20W + 15% = 92W
→ Select 100W transformer
Controlled transformers
| Control | Power ratings | Usage |
|---|---|---|
| RF | 30-200 W | Remote control, wireless wall push buttons, white, no applications, 4 on the same button |
| Zigbee | 30-200 W | Remote control, wireless wall buttons, white and black, smart home (e.g. Hue) applications |
| DALI | 30-200 W | Professional use, bus cabling |
In addition, a controller 20-40A (480-960W 24V) is available for all, to be installed between the transformer and the CCT luminaire
Summary
- With CCT technology, only one LED circuit operates at a time → consumption is half of rated power
- Spots and panels are indicated with actual consumption
- For strip lighting, the product name includes the sum of the LED circuits - use the max. input power(Req. P in the tables)!
- Remember +15 % safety margin
- Select transformer based on power and control