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Email This Page to a FriendPreview: Boat Wiring, Part 3 – Wire & Electricity
January 17, 2013
Don presents a clear way to determine the proper type and gauge of wire to use on your next boat wiring job as well as the basics on amperage, voltage, and resistance in this video on proper boat wiring.
– [Narrator] Our series on marine electrical systems rolls on with our guru, Don Eley. As he describes different kinds of wire and helps us to understand which ones to use for our own projects.
– It seems that wiring on board is really one of the biggest challenges that we have. We’ve got corrosion problems, we’ve got vibration, and things like that that really challenge the whole wiring system onboard. So today, what we’re gonna do, first off, is look at some different types of wire, and believe it or not there are three different types. This is actually called Type One, and you might be familiar with this. It’s Romex, or household, wiring. It’s single conductor, this happens to be the ground. It’s singled wire, solid core. And this is not appropriate for marine use. And the reason is the wire itself, being single-strand like this, during vibration will break and then we’d have a bad connection. So, we don’t use single-strand wire Type One wire on board a vessel. In fact, both the Coast Guard and the American Boat and Yacht Council, prohibit the use of Type One wire. So, that’s not appropriate. Type Two wire, typical automotive wire, it’s multiple strands and it’s appropriate for marine use. It has a few challenges. One is is it’s not as vibration-resistant as other Type Three wire that we’re gonna look at here in a minute. And it also is just straight copper. It doesn’t have any tin coating, so there’s no corrosion inhibiting factor to this wire. It is appropriate for marine use when we don’t have high vibration. Type Three, you’ll see has actually even more strands. And this is what I consider most appropriate for marine use. It can handle high vibration. It’s also the copper is tin-coated, so that inhibits any corrosion that we might have on the copper. So we get a better connection because of that. So, Type Three wire is what we’re gonna be using today in all of the connections that we’re making, because of its superior performance, I guess, in a marine environment. Alright, so now we wanna look at a wire gauge, which is actually the circular area of the surface of the cross-sectional area of the wire itself. So we’re looking at, again, Type Three wire. This happens to be ten gauge wire. And it’ll actually tell us that on the wire itself, that it’s 10AWG, that’s American Wire Gauge. That’s a standard for measuring that cross-sectional area of the wire. And again notice this is multi-strand in tin, so it prevents corrosion. So that’s Type Three 10 gauge. In this particular case, I have red and a yellow, and this is the convention now for low-voltage DC. So 12 and 24 volt DC. We’re gonna be using red for the positive side and yellow for the negative side. And that allows us to avoid any confusion that we might have with a high-voltage 120 volt short power or generator power that we use red and black and white in those conventions. So, DC low-voltage, we’re gonna be using red for the positive, yellow for the negative. So that’s 10 gauge. As the number goes up, we’re gonna actually get a smaller diameter wire. So this one here’s a little bit smaller, this is 12 gauge. It’ll be a little bit smaller than a 10. This is our 14, both Type Two and Type Three 14 gauge. We continue to get smaller here. This is 16 gauge, which is pretty much the smallest that you typically see on board a vessel. And then the smallest one we have here is 18 gauge. So, again, as the number gets larger, that cross-sectional area actually gets smaller, the wire’s smaller. Now the wire gauge that we’re gonna use is a function of the amperage, or the current flow. The rate of electricity flowing through the wire. So the greater the rate of flow, the higher the current flow the larger the diameter we want. But of course that’s a smaller gauge wire. One other thing we should look at is some of the information that’s available right on the wire insulation itself. In this particular case, we’ve got the manufacturer’s name, we’ve got 10 AWG, so that’s 10 American Wire Gauge. So it meets their standards. is Underwriter’s Laboratory boat cable. That means it’s meeting Underwriter Laboratory’s standards for boat cable, which happen to the Type Three, which is the one with multiple strands, and tinned copper, so that’s what meets their standards. The insulation is rated for 600 volts. We’ve been using this in a 12 volt system. It’s just telling us that the insulation itself has that capability. 105 degree Celsius dry and 75 degrees Celsius wet. Those are conditions that the wire itself and insulation can withstand and still be in a safe mode. It’s oil-resistant, and then there’s another list of numbers here that meeting some other standards. But this gives us some great information right on the surface of the insulation. Alright, so now we’re gonna talk a little bit about electricity and this kinda relationship between voltage, amperage, and resistance. And I think most of you are familiar with Ohm’s law, which states that voltage V = A x R and we can rewrite that a couple of different ways easily. Amperage, which happens to be the rate of flow of electrons through the wire, is equal to the voltage divided by the resistance. And then lastly we can look at Ohm’s law another way which is resistance is equal to the voltage divided by the amperage. And this gives us this relationship between voltage, which is the electrical pressure, amperage, which is the rate of flow of electrons through the wire, and resistance of either the wire itself or some device that’s in that circuit. So if we have a battery, typically it’s a 12 volt battery, we’re gonna have a positive terminal and a negative terminal. And we’re gonna have some load over here. We’re gonna call this our Load. And typically we’re going to run a wire with a switch to our load, and then from our load back to our battery to the negative side. Typically we switch things on the positive side of the circuit. And if we close this switch then electricity’s gonna flow from our battery, through our load, that could be a bilge pump or a fan or a GPS, whatever. And then back to our battery. And we need this complete circuit for this electricity to flow. So when we’re determining wire size, or wire gauge, we need to know several things. One, we need to know the battery voltage. We need to know the length of run that this electricity is gonna take from the battery to the load and all the way back to the battery. That total length of run there. And we’re also gonna need to know the amperage. How much amperage this actual particular load is gonna draw. And that’s gonna be a function of the resistance also in this entire circuit. So the next thing we’re gonna do then is we’ll go to a table and determine what gauge wire we should be using for this particular circuit based on this amperage, based on this voltage, and based on this length of run that we have here within the entire circuit. Alright so the next step then is to determine what wire gauge is appropriate for the particular load that we have in the circuit. And so one source of that information is the American Boat and Yacht Council Standards and Technical Information Reports for Small Craft. And if we go to Section E11 of this publication we actually find a table here that’s going to talk about, or demonstrate anyways, this relationship between voltage, amperage, and length of run. And then from that table we’ll be able to determine our wire gauge. So for example, in the circuit that we were just looking at this happens to be the 12 volt 3% voltage drop wire gauge table that we’ll be using. If it draws five amps, and we have a total run of, let’s just say 40 feet, so 20 feet from the battery to the device, let’s say the bilge pump, and back again. So if it draws five amps the total run is 40 feet. It’s telling us we should be using 10 gauge wire for that particular application. So that’s how we use the ABYC table for determining wire gauge based on voltage, amperage, and the length of run of the particular circuit. So the ABYC table is divided in to 12, 24, and 32 volts. This is what we consider low-voltage DC, direct current. This is what’d be used in a battery situation on a boat. And I imagine you could find this online fairly easily also. This is pretty basic information that’s available.
– [Narrator] So we’ve gotten through the basics of wire of all sizes and electricity. Our next installment we’ll get in to making good, solid connections with them. See you then.