Always double check to make sure your printer is unplugged and the capacitors in the power supplies have discharged before touching any wire or terminal. This is why planning should be done in detail before you rush out to buy things like cables.When wiring your printer electronics, you will be working with line voltage wiring (120V / 220V AC). The point is to design your system using a safe wire size but also to be conscious of the trade-off between system voltage, wire length, line losses, and costs. This reduces the amps which reduces the wire losses. Another option is to operate at a higher voltage, such as 24V. Sometimes we have to tolerate perhaps a 4% loss rather than 2%, allowing us to double the length values shown in the table. Many people have long cable runs and don’t realize the impact this has on performance. What this example illustrates is that we need to greatly appreciate the issue of cable length and its effect on losses. Next, we look at the Array amps column, select row “25” and you can see that a 10 AWG wire pair only supports a cable length of 4.5 feet! Going up to 4 AWG supports up to 18 feet to stay within the 2% loss criteria. It is rated at 30 amps, higher than the required 25 amps. Looking at the wire capacity row, 10 AWG is the smallest gauge wire that can safety be used. At the Vmp of 18V, the maximum current is 450/18 = 25 amps. You can double the length for a 24V system, or quadruple it for a 48V system.Įxample: Let’s take a 450-watt 12V system. Here is what that calculation looks like for a 12V PV system. Using the known resistance of the various wire gauges, it is possible to calculate the maximum length for a wire-pair for each wire gauge size. The general rule-of-thumb is to stay below 2% Voltage drop on this run. Since all of the combined PV power flows through this wire set, we really need to choose it correctly to maximize performance and to assure safety. Usually the longest wire run is from the PV array to the location where the charge controller or GTI is located. If this is not done, then the battery bank’s life can be shortened and certain safety issues can result. It is very important to match the gauge and the wire lengths when combining batteries in a battery bank. A typical battery bank wire size is 1/0 or “one-ought.” These same wires will also have to carry current used simultaneously for charging and for power inversion. The wires between batteries in a battery bank tend to be the largest in the system since they are used in conjunction with a power inverter that can at times demand more current than that the PV system can supply on its own. Refer to the installation material for the charge controller you chose when selecting the correct wire size to use. These Charge Controllers have large transformers that lower the voltage but in the process they increase the current going to the battery bank. The exception (B*) is when the Charge Controller is of the type that can operate a 12 or 24-volt battery bank even when the PV array is operating at higher voltages, such as 48 Vdc and larger. The wires from the charge controller to the battery bank can generally be the same or larger gauge than the main set from the PV array. If multiple panels are combined in parallel, then a three to eight AWG “combiner” wire set is generally needed to safely transfer the power to a charge controller or GTI. This allows up to 30 amps of current to flow from a single panel. The chart below shows the capacity of various wire gauge sizes and their typical amp rating and application for both residential and solar applications.Ĭommercial solar PV panels over 50 watts or so use 10 gauge (AWG) wires. The lower the gauge number, the less resistance the wire has and therefore the higher current it can handle safely. If your electrical wires (the copper gauge) are not large enough or if the cable is longer than needed, then the resistance is higher resulting in less watts going to either your battery bank or the grid.Ĭopper wires are sized using the gauge scale: American Wire Gauge (AWG). Longer hoses have more resistance than shorter ones of the same diameter. Moreover, even with a large diameter hose, shorter hoses have better flow than longer hoses. The larger the diameter of the water hose, the less resistance there is to water flow. In addition, if the wires are undersized, there is a risk that the wires may heat up to the point in which a fire may result.Īn electrical wire carries current much like a water hose carries water. If the wires are undersized, there will be a significant voltage drop in the wires resulting in excess power loss.
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