Electric Cable & Fuse Sizing - Camper Van Conversion Series

good morning guys welcome to the workshop today's video i want to talk to you about electrical wiring cable sizing and fuse sizing i'm using the new osmo action camera today as you can see you get a lot more of the workshop in the field of view and probably a lot more of me as well but i don't know if that's such a good thing i have put on a bit of weight lately now i know lots of you guys are doing your own van builds at the moment taking full advantage of the lock down and not being able to work to get on with your own van builds and what i thought i'd do to help out because by far the most questions i get about electrical wiring about cable selection cable sizing fuse sizing how to wire circuits and i've actually spent a lot of time with a number of people that have come to me for advice and done dedicated wiring diagrams helped them with cable sizes and so forth so i thought it'd be really good to put together a video that would help all of you guys that are struggling with your electrical wiring of your van what i've also done recently is i've created a dedicated playlist for this type of video where it's not specific to just my van it's relative to everybody's van so all of the little workshop videos i've done on solar power electrical wiring plumbing water whatever it might be if it's non-specific to any particular van if it's just a general workshop video i've put those in one playlist and at the moment i think there's 10 videos in that playlist covering all sorts of different subjects so if you're looking for some really useful help and advice to get your van build underway then have a look at that playlist of videos i've got there now one thing you can always guarantee when you watch any of my videos is that the information that i put out will be current and it will be correct i always refer to the latest regulations whenever i'm doing any of my videos because i know the importance of my information is going out there to thousands of people you're watching what i'm doing and you're potentially going to be copying what i'm doing so the information i put in my videos has got to be factual it's got to be current and it's got to be correct so you can guarantee that if you watch any of my information you know it's going to be been up to date you know it's not going to be something i've just watched somebody else doing for oh no i'll copy what he's doing even how it could be wrong obviously if you're viewing this from another country you might need to check what your local wiring regulations are or where you are but to be honest the british standard for wiring is a really good base so if you're following these instructions you'll be fairly safe okay the first thing i want to talk about is cable selection and what you should be using in your van i've seen a lot of people use this which is twin enough or household wiring it's basically a solid copper core inside pvc sheaving and it's what's normally used to wire your house and i've seen a lot of people use this in the van now the main reason that you shouldn't really use this in your van is because your van's moving around a lot obviously bumpy roads you know some of the cobblestone roads that we went on in portugal and that i wondered whether we'd have a van left at the end of it so it's going to be subjected to a lot of vibration and what happens with these single solid core cables if that flexes a lot eventually that copper work hardens and then it just breaks and that's your only source of power that single core so if that breaks in your van that device or whatever that's powering is going to be no good and then you've got to then trace that and replace it so that's why this you know just don't use this twin enough it's meant for household wiring it's not meant for vehicles what's best to use are flexible cables like i've got here this is a rubber sheaved cable gives you loads and loads of protection and if we look closely at the cores of these see if i can hold this up to the camera they've got multiple cores loads and loads of strands in there so and they're very very flexible you know because you've got loads of tiny little cores in there so you're not going to break these these are going to last a lot longer in your van these subject leads to loads and loads of vibration these will be fine and even if you do break one or two of these tiny little cores you've got loads of other ones to still conduct your electricity so multi-stranded flexible cables is what you need to be putting in your van what i've got here is i've got a rubber sheaved cable which gives you very good protection against wear and this other cable with this blue cable is called arctic blue and this covers a wider range of temperatures as well i think this will go down to about -40 so particularly for outdoor use and the van is really an outdoor use you know we could be subjecting it to some cold temperatures this cable is really more suitable you know it will last a lot longer in your van and then another thing that we ought to be considering is how we're going to protect the cables because you're pulling cables through the van the van's metal some of those edges in your van are really sharp you know they're like little knife edges and if your cables are rubbing up and against those knife edges for any length of time it's going to wear through the cable so if you drill in holes through your van to pull cables through you really need to be putting some protection on there now what i've done in our van is i've installed this pvc conduit you can buy it in sort of 10 meter rolls very cheaply i think about six or seven pounds and then pull this through the band first and then feed your cables through this and this will offer like loads of protection for those cables so when they're getting shaken around in the van they're not going to wear out the other advantage of this is it's some kind of future proof shevan as well because if you need to change your cables for whatever reason or you need to add another cable you can always fish another cable through this conduit and we actually needed to do that because our temperature sensor cable wasn't long enough i put the conduit in and luckily i could pull another cable through and then more recently we've added another couple of extra usb sockets so i've been able to pull some extra cables through an existing conduit to put some extra sockets in the van so it's a little bit you know not much of an expense up front you know 20 30 quid to buy some conduit but it really does make your installation last a lot longer and give you some flexibility to add things at a later date [Music] now if you've already pulled your cables into the van and you're worried that they need a bit of extra protection you can use this stuff which is basically just a uh a pvc coil that you can wrap around afterwards so you don't need to install this first and in fact in the van where the existing wiring loom runs from the front to the back we removed all the plastic trunking now because it didn't suit the cupboard layout and then retrospectively i wrapped the whole of that loom with this pvc protection with this conduit flexible conduit it's a bit of a fiddly job you have to sort of like pull it out and then individually wrap it around it takes a bit of time to do it but it is doable you know and then that will then give that wiring loom a lot more protection so you can add that afterwards so that's another option for you for anything that i'm talking about in today's video i've got a free downloadable pdf in the description of this video with all the information on everything that we've covered and all the links where you can purchase this stuff as well okay so that's cable selection now we need to look at circuit design and then we'll discuss cable sizing and fuse sizing the bulk of the questions that i get from people happen to be about electrical wiring how to wire up everything in their van there are quite a few things that need cabling you know from appliances like fridges cookers heaters you know through to electrical lighting usb sockets solar batteries etcetera you know it can be quite complicated and it can seem like a daunting task and lots of people come to me for a help and advice i have produced a number of different schematics for various different people that have asked me for advice in the past so the aim of this video is to give you a few ideas on how to wire those circuits yourself so rather than help individuals i can help a lot more people so what i've done is i've produced a series of slides on the computer that we'll run through now it will show you how to wire up multiple lighting circuits it will show you how to wire up multiple usb sockets where to position switches and then after we've gone through those slides i'll then talk about how to size those cables and how to size your fuses correctly okay so we're going to start off with some simple basics first of all we have our power source which in the case of our camper vans is usually a leisure battery 12 volt with a positive and negative terminal next we have our loads these are the devices that use the electricity they can be fridges tvs sockets lights anything that we need to power and then to complete the circuit we have our conductors or our 12 volt wires to connect the positive and negative from the battery to the load this completes the circuit and electricity can now flow from the battery to the light however in this case if we were to wire it like this the light would be on all the time so we need some way of controlling you the easiest way to do that is to break the positive wire to the light and install a switch you could break either the positive or the negative conductor to make or break this circuit and to switch the light on and off but the normal convention is to switch the positive because that will be carrying the 12 volts the negative is usually zero volts on dc circuits the only thing we need to add to this circuit is a fuse to protect the cabling and we'll come on to that next because we normally have a lot of devices to power in our campervans it's usually best to fit a blade fuse holder this will have one common positive input and multiple outputs which can each be individually fused the ones i like to use also have a common negative bar to bring all of the negatives back to one position okay let's say we have a number of lights in our van that we want to wire together on one circuit each light will have a positive and negative wire so we need to find out the best way to wire these together now if you just wired from one light to the next light in series and then wired back to your blade fuse holder the lights would work but you'd find that the first light would be very bright and the last light in that line of series would be really dull because you'll get a voltage drop along those cables this is not the correct way to wire lights the best way to wire the lights is to connect all the negatives together and connect that back to the common negative on the blade fuse holder connect all the positives together and connect that to one of the free fuse slots you can add a switch into this positive wire if you want to control them and that completes the circuit the lights are now wired in parallel so basically all you do is take a two core cable to the first light and then put a two core cable from light to light connect all the blacks together at each light and connect all the reds together at each light and that way they'll be wired in parallel every light will see the same voltage and every light will be the same brightness so that completes the circuit the lights will all now work off of that switch and all we need to do now is work out what fuse size we need and what cable size we need we know from the manufacturer's literature that each of these led lights is 1.8 watts each and as all fuses and cables are sized by the amps we need to use watts law as a little equation to work out how many amps that would be what's law states that the power in watts is equal to the voltage times the current in amps and we can rearrange this equation so that we can get a result for the amps an easy way to swap equations around is to put the equation inside a circle as i've shown here and then you simply remove the item that you want to find out and then the rest of the equation is shown for you as follows if we want to work out what the watts are it's volts times amps if we want to work out what the volts is it's what's divided by amps and if we want to work out what the amps are it's what's divided by volts so you can see there quite easily by having it in that little symbol it makes swapping these equations round really simple okay so eight lights times 1.8 watts equals 14.4 watts that's the total power for the eight lights we take the 14.4 watts divide by the 12 volts because it's a 12 volt system and that gives us 1.2 amps so we now know that when the lights are switched on they'll be drawing 1.2 amps from our leisure battery now normally fuse sizes cannot be more than one and a half times the total load on the system so i'd like to go somewhere in the middle of that at 1.25 or 25 bigger than the load so we take the total load rating in current of 1.2 amps times by 1.25 which basically adds another 25 percent and that gives us a fuse rating of one and a half amps blade fuses come in half an amp one amp two amp and so forth there isn't actually a one and a half amp blade fuse so we will have to go up to a two amp fuse for this circuit if we were to put a one amp fuse in this circuit as soon as we turn them on the likelihood is that would blow and then with regards to the cable sizing we simply look up the cable rating in a table taking out of the british standard which i'll show you towards the end of this video and for this load a cable size of 1.5 millimeters squared is more than adequate and the cable size needs to be rated higher than the fuse rating in the event of an overload the fuse would blow before the cable was damaged now it's very important that you size the cables correctly they need to be much larger than the load and much larger than the fuse size if you try and put too much current through a small cable you severely risk burning that cable out and it could potentially catch fire it's never a bad thing to slightly oversize your cables if you're unsure always go up to the next size okay let's say you wanted to install a number of usb sockets into your van again each socket would have a positive and negative connection and as before you'd take a two core cable and wire them in parallel so you'd run two core cable between each of the sockets you'd connect all of the black cables to the negative and all of the red cables you'd connect back to an available blade fuse terminal and as we did for the lighting circuit if you wish to control these sockets you can also install a switch to break that positive supply now these sockets have a higher rating in amps they're dual sockets each socket has a 1 amp usb and a 2.1 amp usb so if you were to use both of them on a socket each socket could potentially pull 3.1 amps therefore with four sockets wired onto this circuit that's four times 3.1 which gives us a total load of 12.4 amps so if you were to plug in devices into every usb outlet you could be drawing 12 and a half amps from your leisure system as we did before to size the fuse for this circuit we multiply by 1.25 so that puts 25 percent safety margin onto the rating and gives us a fuse size of 15.5 amps the nearest available fuse size for that is 15 amps as it's only 0.5 of an amp below our safety margin i would go with a 15 amp fuse rather than going up to a 20 amp fuse and then you simply continue wiring all of your other appliances in the van in a similar fashion you take a positive and a negative from the blade fuse holder to the appliance you put a switch in the positive if you want to separately isolate it or control it and then a suitably sized fuse in the blade fuse holder the only difference is when you come to fridges and fans which have electric motors fridges have compressors and when a motor starts there's normally a surge current it takes a lot more power to get the motor going initially so you'll find that there's a higher starting current so it's always best to refer to the manufacturer's literature they'll normally tell you what the recommended fuse rating is for example our 12 volt compressor fridge this normal running current is somewhere between 5 to six amps but the manufacturers recommend a 15 amp fuse because of the compressor starting current then as you work back through the system towards your batteries you simply add all of the loads together to get a total load for the cable and fuse sizing for the battery connections you've got to assume a worst case scenario that all of your lights and all of your sockets could be in use at the same time so that cable from your battery to your blade fuse holder needs to be large enough to run everything simultaneously that's why you'll see in a lot of systems you'll see larger cables going from the battery to the fuse holder and typically in this installation you'd have something like a 10 mil cable battery cable which is good for up to 70 amps and something like a 50 amp fuse onto the blade fuse holder because you could have multiple circuits coming off there and when you add them all together the amps do increase quite quickly now let's just go back to that cable sizing chart from the british standard because there's another factor that we need to take into consideration when we're sizing our cables you can see on the table down the left-hand side is the cross-sectional area of all the cables and then each of the other columns is the current rating in amps now this varies depending on how we've installed our cables if we've just clipped them on the surface in the open air then the cable is going to stay fairly cool and it can handle quite a lot of amps if we've put it inside a conduit then it can carry slightly less amps because there's a chance for the cable to get warmer and then if we've buried the cable in a wall with insulation there's a possibility for the cable to get even warmer still so the current carrying capacity goes down even more so depending on where we've put our cable and how we've installed it that'll depend on how many amps we can put through it and you'll see on the table the figures from left to right actually get smaller i'll put a free pdf copy of this chart in the description below this video so i hope you found all that information to be useful i know it's been a bit of a longer video and thank you for sticking through right to the end but hopefully you know that's given you tons of information to give you a bit more confidence to tackle your own electrical circuits if you see people on social media and they're asking questions about electrics please do give them the links to my videos and hopefully that'll also help them out too have a look at that playlist that i've created because there's tons of more information there not just about electrics but about plumbing solar water services you know everything that's relative to your van insulation whatever it might be i put a dedicated playlist there of useful factual information so make sure that you check out those videos as well don't forget that there's loads of free pdfs in the description there's electrical wiring schematics there's material lists there so there's loads of information in the description of this video that you can download which will also help you out and if there's anything else that you want to know or you want to ask me any questions about today's video then please do leave them in the comment section below i love reading all of your comments and i always try and answer as many of them as i possibly can so lastly it just remains for me to say thanks very much for watching the videos guys i hope you're all taking care of yourselves in this current situation and i look forward to seeing you all very soon thanks a lot cheers

Channel: Greg Virgoe

Views: 871,301

Keywords: Greg Virgoe, #vanlife, Mercedes Sprinter, tiny home, full time van life, self build camper van, off grid living, how to wire your camper van, how to wire 12v electrics, how to wire solar systems, cable sizing, fuse sizing, cable selection, how to wire a van, leisure battery systems, 12volt wiring, how to wire basic circuits, watts law, BS7671 sizing chart, How to wire USB sockets, 12volt electrics, off grid wiring diagrams, artic blue cable, wiring blade fuse holder

Id: koFg6oFs0RU

Length: 22min 45sec (1365 seconds)

Published: Fri May 15 2020