Round Twin 2 Core Cable 12v 24v Thin Wall Wire (25 AMP Rated 2mm²) 30 Metre

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This chart works for any voltage or voltage drop, American (AWG) or metric (mm2) sizing. It applies to typical DC circuits and to some simple AC circuits (single-phase AC with resistive loads, not motor loads, power factor = 1.0, line reactance negligible). Expressed in mm² and describes the tota l cross sectional area of the copper conductor. You will sometimes see cable described as 1mm or 2mm cable without the ² sign but it is important to note that this does not mean the diameter of the cable. This can often lead to confusion so just remember that the main specification for a cable will be its conductor's cross-sectional area and cable will never be referred to by its diameter alone. Low voltage automotive and marine cable is available in different materials/constructions and the following table gives a brief overview: Material This is the resistance of the conductor expressed in Ohms per metre ( W/m) and is important when determining voltage drop (see below) It has sufficient current rating for the expected load in the circuit, including a margin of safety.

Step 2– Determine appropriate wire size from the chart below. Compare your calculated VDI with VDI in the chart to determine the closest wire size. Ampacity rating of wire size must be at least 125% of the continuous current passing through it. In Europe, metric sizes are used for stranded cableand are expressed as the total cross sectional area of the conductors together with the number of strands and their diameter. For example, a cable specified as 2.0mm² 28/0.30 indicates that it has a total conductor cross sectional area of 2.0mm² and is made up of 28 individual strands, each of 0.3mm diameter.This problem is overcome by manufacturing the core from many small diameter strands of copper wire to make up the desired cross-sectional area, rather than using a single wire. This type of cable is (unsurprisingly) known as 'stranded' cable and provides much more flexibility, which means improved resistance to work hardening making it better suited to use in vehicles. The difference in cross sections is shown in the diagram below: So we want to select a cable to make sure that the voltage drop is not so large that it will cause problems, but what is acceptable and how do we calculate the right cable size to use? Well the generally acceptable voltage drop for DC circuits is around 3-4% and we can use V = IR (see Electrical Circuit Basics) to calculate the voltage drop for a cable if we know the current draw of the load and the cable's resistance per metre. NOTES: AWG = American Wire Gauge. Ampacity is based on the National Electrical Code (USA) for 30°C (85°F) ambient air temperature, for no more than three insulated conductors in raceway in free air of cable types AC, NM, NMC and SE; and conductor insulation types TA, TBS, SA, AVB, SIS, RHH, THHN and XHHW. For other conditions, refer to National Electric Code or an engineering handbook. HIGH VOLTAGE PV MODULES: Consider using higher voltage modules (18+ volts peak power point, like our BP-585 and BP-590) to compensate for excessive voltage drop. In some cases of long distance, the increased module cost may be lower than the cost of larger wire. PV-DIRECT SOLAR WATER PUMP circuits should be sized not for the nominal voltage (i.e. 24V) but for the actual working voltage (in that case approximately 34V). Without a battery to hold the voltage down, the working voltage will be around the peak power point voltage of the PV array.

Expressed as the number of conductors of a given diameter. So 28/0.30 means that there are 28 strands, each with a diameter of 0.30mm The table below provides a cross-reference between these two standards, showing the closest metric equivalents to each Gauge for cable sizes commonly used in low voltage automotive and marine applications. AWG ALUMINUM WIRE may be more economical than copper for some main lines. Power companies use it because it is cheaper than copper and lighter in weight, even though a larger size must be used. It is safe when installed to code with AL-rated terminals. You may wish to consider it for long, expensive runs of #2 or larger. The cost difference fluctuates with the metals market. It is stiff and hard to bend, and not rated for submersible pumps. There is a general rule of thumb that says if you're unsure whether the cable is large enough for the job, go up a size. This is a bit crude and not very scientific but it's not a bad rule to apply as increasing cable size can't do any harm.PV BATTERY CHARGING CIRCUITS are critical because voltage drop can cause a disproportionate loss of charge current. To charge a battery, a generating device must apply a higher voltage than already exists within the battery. That’s why most PV modules are made for 16-18V peak power point. A voltage drop greater than 5% will reduce this necessary voltage difference, and can reduce charge current to the battery by a much greater percentage. Our general recommendation here is to size for a 2-3% voltage drop. If you think that the PV array may be expanded in the future, size the wire for future expansion. Your customer will appreciate that when it comes time to add to the array. Did you know altE offers free solar system design consulting? Call us at 877-878-4060 or tell us about your desired system using our free quote tool.

If we wanted to wire up a light that we know has a power rating of 50W, then using I = P/V the current draw would be 50W/12V = 4.17A. This tells you that you could use a cable with a rating of 4.17A or above, however it is good practice not to design a circuit operating at the upper end of the cable's rating and so you should select a cable with some additional capacity. In this case 0.5mm² (11A) cable would be appropriate.Anyway, enough maths - to make it easy we've developed this handy calculator which will show you the approximate voltage drop based on cable size, supply voltage, current draw and cable length. In most situations the detrimental effects can be minimised by using shrink sleeving, sealed connectors, adhesive lined terminals, protective gels etc. to keep moisture out, but in some applications where the environment is particularly aggressive, for example marine use, it might be preferable to use cable with tinned conductors. This is simply where the standard plain copper conductor has has a layer of tin applied before being sheathed in the insulation.Tin doesn't react in the presence of moisture, yet retains good conductivity, and so improves long-term performance of the cable. The downsides are that it is slightly more expensive and there is a more limited range of sizes and colours available compared with plain copper. Earth braid straps that have no insulating layer are typically tinned for protection as a matter of course. This shows that 1.5mm² cable (at a current rating of 21A) will be suitable for the cable run length as the drop is well under 3% The results for British standard cable are calculated from BS7671 (18th Edition) Requirements for Electrical Installation, IEE Wiring Regulations, and are based on 230V and 415V voltage drop. It covers Low Voltage armoured AWA and SWA cables, insulated cables including twin & earth and 6491X, and insulated and sheathed cables in both PVC and LSZH such as H07ZZ-F and SY cable.

You might find it useful to read our Electrical Circuit Basics article for using the equation I = P/V where the following example is given: Expressed in Amperes (Amps or A) and is the maximum continuous or 'working' current that the cable can safely carry. Eland Cables' Cable Calculator can help you determine the most appropriate cable size for your installation against British and IEC standards. Complete the sections below to calculate your results. DC MOTORS may be used in renewable energy systems, especially for water pumps. They operate at 10-50% higher efficiencies than AC motors, and eliminate the costs and losses associated with inverters. DC motors do NOT have excessive power surge demands when starting, unlike AC induction motors. Voltage drop during the starting surge simply results in a “soft start”. Each component or appliance connected to a circuit will have a current draw associated with its operation and it is important that the cable supplying power to these is capable of carrying the normally expected current, plus a margin of safety. If it is not capable then it is likely to result in the cable becoming hot and potentially catching fire. Although fuses are used in the circuit to protect the cable, the cable itself should be of an adequate rating to prevent this over-heating occurring under normal circumstances.LIGHTING CIRCUITS, INCANDESCENT AND QUARTZ HALOGEN (QH): Don’t cheat on these! A 5% voltage drop causes an approximate 10% loss in light output. This is because the bulb not only receives less power, but the cooler filament drops from white-hot towards red-hot, emitting much less visible light. This shows that although 0.5mm² cable is OK for the expected current draw of the light, it's not OK for the cable run length as the drop is greater than 3%. All elements of an electrical circuit have resistance, including electrical cable, which means that there will be energy loss in the form of voltage drop experienced along the length of the cable. Just as a bulb converts electrical energy into heat and light due to its resistance, and so induces a voltage drop, a copper conductor has resistance and will convert some of the energy it conducts, causing a voltage drop in the same way. The difference is that voltage drop across a bulb (or other load) is useful as that's what makes it work, but voltage drop along cable and other passive parts of a circuit is not desirable as it's not a useful conversion of energy.