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%

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. 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. The cable size results for International standard cable are calculated from IEC 60364-5-52: Low Voltage Electrical Installations, selection and erection of electrical equipment – Wiring systems and are based on 230V and 415V voltage drop. In both BS and IEC calculations, the KW calculation is based on a power factor of 0.8.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. 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.

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.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.

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. Thirdly, the harder grade of PVC is more reistant to abrasion and cutting than standard PVC, offering more protection and greater reliability. 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. It has sufficient current rating for the expected load in the circuit, including a margin of safety.

Determining Tolerable Voltage Drop for Various Electrical Loads

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. In North America the AWG standard is most commonly used for stranded cable and expresses the Gauge together with the number of strands and their Gauge. For example, a cable specified as 16 AWG 7/24 has a size of 16AWG and is made up of 7 individual strands, each of 24 AWG.

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.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: 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.