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Hi, this is George with Argo electrical services and this is our podcast on voltage drop explained. So, voltage drop happens when the voltage at the end of a run of cable is lower than at the beginning, any length or size of wires will have some resistance and running a current through this resistance will cause the voltage to drop as the length of the cable increases. So does this resistance and reactance increase in proportion. Hands voltage drop is particularly a problem with long runs of wire or cable. For example, in larger buildings, or on larger properties such as farms, this technique is often used when Properly sizing conductors and any single phase line to line electrical circuit. This can be measured with a voltage drop calculator. I know in our business we do a lot of circuits that run from houses three, four, maybe even 500 yards down to a dock on Lake Lanier and you know we we get a lot of troubleshooting, where guys have run number 12 wire sets 400 yards to get 20 amps down at a dog. Well, it’s just not possible you’re you’re not even getting 100 amps down there. electrical cables carrying current always present inherent resistance or impedance to the flow of current voltage drop is measured as the amount of voltage loss which happens through all or part of a circuit. When cable impedance involves happens, too much voltage drop in a wire can cause lights to flicker or burn dimly heaters to heat poorly or motors to run hotter than normal and burn out. This occurrence will cause the load to work harder with insufficient voltage present in the present, present the current. Also, we work on a lot of you know, three storey four storey homes here around the lake in Gainesville and coming. And these guys will have two panels mounted in a basement and then run circuits all through the house. And by the time it gets to the end of the circuit, it might be 200 feet before it gets to the end. And we’ll maybe you’ve got a computer set up in an office off of bedroom. In any event, the computer’s not getting the maximum amount of voltage and you know and it’s going to make the fans work harder the CPU is not going to work is effectively and voltage drop is not a good thing. So how do we solve voltage drop to eliminate voltage drop in a circuit we need to increase the size of our conductors. This is done to lower the overall resistance of the cabling. Certainly larger copper or aluminum cables sizes increase the cost of your project. So it’s important to calculate voltage drop and find the best voltage wire size that will reduce voltage drop to safer levels while remaining cost effective. How do I calculate voltage drop to calculate voltage drop, you can use the voltage drop formula which is V equals I times R where V is is the voltage aah is the current flowing through the conductor or amps and R is the resistance of the conductor or ohms. By knowing the current resistance and length of the conductor you can calculate voltage drop and determine whether it falls within acceptable limits. How is voltage drop calculated in a circuit voltage drop is calculated circuit using Ohms law which we just stated, which states the voltage drop across the conductor is equal equal to the reciprocal of the current and resistance. By knowing the current resistance and the length of our conductor, we can calculate the voltage drop and determine whether it falls within limits we can live with in our current application. I know on commercial jobs, a lot of the three phase systems utilize three phase 120 208 systems, some AC heat HVAC units, and other large equipment will run on 243 phase or 208 As long as you’re within approximately 10%. That will work because originally those were two 30 volts circuits across three phases not to 40 some of the newer systems will not work. Why is it important to calculate voltage drop, calculating voltage drop is essential in maintaining an efficient and safe electrical system. Voltage drop can impact the performance of electrical equipment and devices leading to hazards such as fires and electrical shock. By calculating voltage drop accurately, engineers can choose the appropriate wire size, cable link and other specifications necessary to maintain an efficient and safe electrical system. And let me back up they’re generally on residential and a lot of small commercial jobs, there is no electrical engineer, so your electrician or your electrical contractor does the engineering. Now, there are many jobs that I go to that we install new services, service upgrades and you know, we’re supposed to do a load calculation on this and this is all part of it. And improperly doing this can cause your customers new property, burn up air conditioning units, burn up washers, dryers, stoves, all kinds of stuff. You know, so, this is a very important thing of what electricians do. What are some advantages of utilizing voltage drop calculators using a calculator that determines voltage job can deliver several benefits including accurate calculations time savings, cost free drug duction and hazard prevention I II if my AC unit last six years longer than it would have by using a wire that just wasn’t big enough because of the distance I have saved my customer money and therefore I have built returned business for my my business. Okay, where are we at voltage, inundation and calculating voltage drop accurately can reduce potential electrical hazards such as fires and shock. They will also ensure longevity and machinery after installation. Are there any limitations to using a voltage drop calculators, why voltage drop calculators offer many benefits there are some limitations to using them. For example, they rely on the accuracy of the input parameters. They might not consider other factors that can affect voltage drop, such as such as temperature and ambient conditions. Also these calculations may not be suitable for more complex electrical systems, what is the voltage drop per 100 foot the voltage drop per 100 foot depends on various factors including the current following through the conductor, the length of the conductor, the resistance of the conductor and the wire gauge your cable size. Therefore, it is essential to calculate the voltage drop accurately to determine the appropriate wire size and cabling necessary to maintain an efficient and safe electrical system. What is a rule of thumb for voltage drop, the rule of thumb for voltage drop is that voltage drop is a circuit should not exceed 3% for power circuits, or 5%. For lighting circuits. These values are based on the National Electrical Code guidelines, ensuring the electrical system operates efficiently and safely. So when I first got into the trade before I ever got my I went back to school when I studied to become a master electrician or a non restricted electrical contractor in the state of Georgia, we always used his rule of thumb 100 125 feet after that we needed to upsize our wire. Well now you can go online with the wonderful internet a wonderful
resource you can use is you can go to South wire.com forward slash calculator dash v drop. So I pulled that thing up on my computer this morning. And so they gotta calculate your voltage drop. So system parameters firstly wants to know are you residential commercial 60 degrees 75 degrees or commercial 90 degrees that’s in your National Electrical Code. columns there when when you’re gauging amperage for wire size and what it’ll cover. That’s where you know that’s what they’re talking about. So, it wants to know about what which current is it DC or AC. units of length of the cable run is it feet or meters will wear in the United States. We’re going my feet is it single phase or three phase we’re using single phase on this one calculation, our conductors copper installation is cable conduit non steel and or direct burial. All right, the input parameters, voltage drop, con conductors, conductor size is number 12, we put in 200 for length of cable run and feet. Voltage we put in 123. Georgia Power around here in North Georgia, if you check across, you know, most of most of the homes around here are somewhere between 121 and 123. If you go cross both legs or be 243 244, all right, and so we put current at the end of the cable run 15 amps because we’re not trying to max out our 20 amp circuit. So I hit Calculate, and it’s a voltage drop 8.47% voltage drop will be limited to 8.74% with a 12, a WG copper conductor, delivering a total of 15 amps and 123 volt phase system for 200 feet. So let’s go back up here and change this to 20. And just see what it says. All right. So when we go to 20 amps, voltage drop is 11.29%. So if we, if we did 11.29% times 123, that’s going to drop us well below what we discussed about 3% for power circuits. So we would at least need to go to a number to Anwar. And let’s go back up here. Let’s put 15 out. And let’s put a number 10 conductor size in here. And let’s see what Alright, so now that is 5.2%. So let’s go on back to a number eight conductor. All right, calculate 3.37%. So now, eight 200 feet. Even if we go with a number eight, we are just getting into the 3% range. You know, I would still say that, you know if I wanted to predict, you know, to get to 2.6% 2.16% we have to use a number six conductor size. So this is George with Argo electrical services. I am the surge protector guy. You can find me at Argoelectrical.com And by all means give me a call at 770-596-1437 Have a great day
