| CSA | Amp rating | Common use | |-----|------------|-------------| | 1.5 mm² | 15–20 A | Lighting | | 2.5 mm² | 24–27 A | Socket rings, 20A radial | | | 32–37 A | 32A radial, small cooker, submains | | 6 mm² | 41–47 A | 40A shower, EV, large cooker | | 10 mm² | 57–64 A | 50A submains |
| Condition | Max continuous amps | Suitable MCB rating | |-----------|---------------------|----------------------| | Free air (clipped) | 37 | 32A (safe) | | Conduit / trunking | 32 | 32A (max) | | Buried direct | 33 | 32A | | Loft insulation (fully covered) | 20 | 20A | | 40°C ambient, clipped | 32 | 25–32A (derated) |
If you are looking at on a standard 240V system, here is everything you need to know about its amp rating and how to use it correctly. The Short Answer: What is the Amp Rating? 4mm cable amp rating 240v
If your appliance pulls more than 30 Amps, ensure your installation method allows for heat dissipation.
The IET Wiring Regulations (BS 7671) categorize ratings based on how the cable is "clipped" or "buried." Here is how a 4mm² cable performs under different conditions: | CSA | Amp rating | Common use
However, if you run that same cable 100 meters, the drop becomes significant, and you may need to upgrade to a 6mm cable to compensate.
Your circuit breaker (MCB) must be rated lower than the cable's capacity to ensure the fuse blows before the cable melts. Typically, a 32A breaker is paired with 4mm² cable. The IET Wiring Regulations (BS 7671) categorize ratings
To figure out if 4mm² cable is right for your appliance, you can use the basic formula: At a standard UK/EU voltage of 240V: 32 Amps can support up to 7,680 Watts (7.6kW) . 37 Amps can support up to 8,880 Watts (8.8kW) .
At 240V, max allowed drop is usually 3–5% (7.2–12V). over 30m at 25A loses ~5V (2%). At 40m → 6.6V (2.75%) – still okay. At 50m → 8.3V (3.5%) – borderline. Long runs may require uprating cable regardless of ampacity.