Note 003 · S1 Parameters · 29 Oct 2026
What a 6.4 × 2.4 m wall actually draws: power, current and heat
Two numbers on the spec sheet decide three things on site: the breaker, the cable and the air conditioning. They are not the same number, and quoting the wrong one is how rooms overheat.
A 6.4 × 2.4 m wall is 15.36 m². At Fortis's 350 W/m² maximum it draws 5,376 W — 22.4 A on 240 V, 44.8 A on 120 V — and 3,072 W at the 200 W/m² average, or 12.8 A. Size the circuit on the maximum and the air conditioning on the average.
Two different numbers, two different jobs
A datasheet gives maximum and average power per square metre, and they differ by roughly a factor of two to three. They answer different questions. The maximum is what the supply must survive on the worst frame — a full-white field, brightness at 100 per cent, all cabinets at once. The average is what the room has to live with over an evening.
Sizing a breaker from the average is the common mistake. It works all year and trips once, at an event, in front of the client. Sizing the air conditioning from the maximum is the other mistake: it doubles the plant for a load that occurs for milliseconds.
The arithmetic on a 6.4 × 2.4 m wall
| Quantity | Working | Result |
|---|---|---|
| Wall area | 6.4 m × 2.4 m | 15.36 m² |
| Maximum power | 15.36 m² × 350 W/m² | 5,376 W |
| Maximum current at 240 V | 5,376 W ÷ 240 V | 22.4 A |
| Average power, upper bound | 15.36 m² × 200 W/m² | 3,072 W |
| Average current at 240 V | 3,072 W ÷ 240 V | 12.8 A |
| Average power, lower bound | 15.36 m² × 100 W/m² | 1,536 W |
| Average current at 240 V | 1,536 W ÷ 240 V | 6.4 A |
Fortis sheet figures used: max 350 W/m², average 100–200 W/m², work voltage 90–240 V. Currents are divided by the top of the voltage range; a 110 V supply doubles them.
The 5,376 W maximum is a worst case that a real controller will reach only on a white field at full brightness. The 3,072 W upper average is the number to hand the mechanical engineer, because LED cabinets turn essentially all of that electrical energy into heat in the room, not into light out of the window.
The rule for the two trades
If the wall will run unattended or on a shared circuit, then size the breaker and cable from the 350 W/m² maximum and add nothing decorative to that circuit. If the room has mechanical cooling, then size it from the 200 W/m² average and treat every watt as heat.
- Take the wall area, not the cabinet count — offcuts and reveals are not lit, so area is the honest multiplier.
- Multiply by maximum power per square metre for the breaker.
- Divide by the nominal supply voltage for current, then check the cable at that current.
- Multiply by average power per square metre for the cooling load.
- Ask separately whether the wall shares a circuit with anything else that draws at the same time.
Where these numbers stop being the answer
1. The supply is 110 V. Current doubles: 5,376 W at 110 V is 48.9 A, not 22.4 A. Fort cabinets accept 90–240 V, so the panel is fine and the site wiring is not — this is the single most common failure in retrofit projects.
2. Your driver power factor is below 1. Then the apparent power in kVA is higher than the real power in watts, and the breaker sees the kVA. Our sheets do not publish a power factor, so we do not quote one: treat the 22.4 A as a watts-based figure and have the electrical engineer confirm kVA on the actual driver.
3. The wall runs a low-brightness schedule overnight. Average consumption falls well below 100 W/m², so a cooling load sized on the average upper bound is oversized but harmless. A breaker sized on the average, however, is still wrong.
4. The cabinets are in an enclosure with no air path. Then the room figure is irrelevant — the heat is trapped at the rear of the cabinet, and the failure mode becomes a driver thermal shutdown rather than a room temperature complaint.
One thing we got wrong ourselves
We used to quote one number, the average, and describe it as power consumption. Clients then sized breakers from it and we spent site visits explaining trips. The sheets publish both figures for a reason, and the correct answer to “how much power does it use” is now two numbers with the job each one belongs to.
- Datasheet — Fortis series sheets, Lite P2.6 / Standard P1.95 / Ultra P1.56: max power 350 W/m², average 100–200 W/m², work voltage 90–240 V, applied to a 6.4 × 2.4 m wall area of 15.36 m². All arithmetic above is multiplication and division of these sheet values.
- Practice — Electrical convention that essentially all input power to an LED wall leaves as heat in the room, and that breakers are sized on worst-case rather than average load. Both are practice, not values taken from a test report.
Questions we get on this
Yes, in practice. 5,376 W is the panel load at full white; the supply also carries driver inrush at switch-on and any de-rating your electrical code requires. The panel figure is the floor, not the specification.
No. Fortis is 100–200 W/m² against a 350 W/m² maximum; Focus is 41–55 W/m² against 205–275 W/m²; Floor is 320 W/m² against 640 W/m². Always take both numbers from the series you are specifying.
No. The breaker is sized for the maximum the wall can draw, and the maximum is defined at full brightness. Operating dimmer only reduces what you actually use; it does not change what the circuit must survive.
Send the wall size and the supply voltage.
We will return the maximum draw, the current at your voltage, and the cooling load — in writing, with the power-factor caveat stated.