How Many Amps Can 4mm Cable Take? (Explained With Example)

4mm cable amps rating

You can’t afford to attach 4mm conductors to applications with larger electrical requirements than they can withstand. You will start a fire. The only way to protect your 4mm wires is to identify the amp rating of the wire size.

How Many Amps Can A 4mm Cable Carry?

4mm cable carries between 17.5A and 37A depending on various factors including type, distance, material, ambient temperature, and installation method.

Situation (4mm2)Amps
Wire enclosed in an insulated wall in conduit26A
Enclosed in conduit or trunking on a wall30A
Thermal insulation in contact with the ceiling < 100mm27A
Thermal insulation in contact with the ceiling > 100mm22A
Thermal Insulation cable touching the wall27A
Thermal Insulation cable not touching the wall17.5A

In other words, even though a manufacturer expects a 4mm cable to carry 37 amps without overheating, other factors can change the wire’s current carrying capacity.

For instance, you cannot expect a conventional 4mm cable in a conduit to transmit 37 amps, especially after burying it underground. The solid tube will restrict the wire’s ventilation. Therefore, forcing the conductors to carry 37 amps is more likely to cause overheating.

Contractors will make a deliberate effort to reduce the current passing through the 4mm wiring to prevent accidents. They may also attach a breaker that trips at a lower amp rating than 37A to prevent consumers from unknowingly exceeding the wire’s capacity.

This is why experts encourage homeowners to use the thickest wires they can find. Thicker wires are less likely to overheat. It is the equivalent of using a wider road because you want to accommodate more cars while reducing collisions.

Talk to an electrician if you don’t know why any of these factors matter or how they influence your cable’s amp rating. You’re not ready to select your own wires. An expert can take the variables in your setting into account before determining the viability of 4mm wiring. There’s no shame in asking for help. Selecting the wrong wire could cost you everything, not just your property but your life.

How Do You Check Amps On A 4mm Cable?

Look at the sheath. Identifying a cable’s ampacity is very simple. The manufacturers will tell you by printing the gauge on the jacket. The gauge matters because most people use this unit to quantify a cable’s thickness.

As such, most ampacity charts use the gauge to show the various wire sizes and their amp ratings. Therefore, if you can find the gauge on a cable’s jacket, you can use it to identify the amps in a chart.

Nicab has a table that shows wire sizes in MM2 and AWG. From that table, you can see that 4mm is the equivalent of 12AWG. The most challenging step is finding the gauge. Once you know the gauge, it will take you a minute or two to figure out the amp rating.

It is common practice for manufacturers to include the gauge on the jacket. But some manufacturers represent the wire size in MM or even inches. In other cases, the wires are so old that the information on the sheath has faded.

If you can’t find the gauge using the information on the jacket, find a table that shows wire sizes in AWG and MM.

The table on the SP Wales platform is particularly fascinating because it wants users to differentiate between MM2 and MM. MM2 is the cross-section, while MM is the overall diameter. 4mm2 equates to 32 amps (Single Phase) and 28 amps (Three Phase).

The closest figure to 4mm in that table is 4.4mm, which also equates to 32 amps and 28 amps, depending on the phase. But again, this is why experts are so important. This information is bound to confuse laypeople that don’t understand the terms ‘Single Phase’ and ‘Three Phase.’

4mm Cable Size VS Amps – Does Size Change The Amp?

Yes, the size changes the amps. In fact, size is the most important variable when it comes to determining a wire’s amp rating. The amp rating tells you the amount of electricity a conductor can tolerate before it overheats.

You cannot identify the current carrying capacity if you don’t know the size of the wire. The NEC has tables that show different wire sizes and amp ratings. Most tables emphasize the gauge. However, you can use any unit of measurement that suits you.

How Many Watts Can A 4mm Cable Take? 4MM Wire Load Capacity in Watts

You convert amps into watts by multiplying the amps and volts. If you want to know the wattage of a 4mm cable, you should start by identifying the voltage.

People in the United States use 120V. Once you know this, you can find the amps. Some manufacturers will tell you the amp rating of their cable. Check the documentation and use that figure to get the watts.

For instance, if your 4mm line has a rating of 37A, multiply 37A by 120V to get 4,440W. If the wiring doesn’t have documentation, look for the gauge on the jacket. Use the gauge to find the amp rating in an NEC table.

If you get a new amp rating, perform the calculations again. The watts won’t stay the same. This is equally true for the voltage. Fortunately, these calculations are pretty straightforward. If you don’t want to determine the wattage manually, find a calculator on the internet.

These tools will convert amps to watts and watts to amps. But you must provide two of the three variables. For instance, if you want the watts, you need the amps and volts. If you want the amps, insert the watts and volts.

4mm Cable VS Volt

No one would blame you for assuming that the voltage matters to a cable’s ampacity. After all, you cannot get the amps or watts without the voltage. However, the voltage doesn’t affect the cable’s current carrying capacity.

A 4mm line will transmit 37 amps regardless of whether your home uses 120V or 240V. The volts don’t matter to this discussion. Your contractor may introduce the topic if they have a question about the insulation. Otherwise, you don’t have to concern yourself with this variable if all you want is the ampacity and gauge.

4mm Twin And Earth Cable Amp Rating

If the cable is in a wall, the amps are 26A. But in the case of the ‘Clipped Direct’ approach, you’re looking at 37A.

4mm Armoured Cable Amp Rating

Armored lines have different classifications, including steel tape, steel wire, and aluminum. Armored cables are typically associated with higher amp ratings. Therefore, don’t be surprised to learn that a 4mm 3-core armored cable can transmit 42 amps

What Is 4mm Cable Used For?

4mm wiring is used for high-power appliances like AC units and kitchen devices.

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