Hi YouTube, my name’s Geoff the VegOilGuy. You may have seen my videos on safely using
a Piggyback Fuse Holder where I let you guys know how you can easily use these simple items
to safely run electrical equipment in your vehicle. Well folks have been asking what
size fuses they can use in a Piggyback fuse holder, or more importantly as – can I overload
the wiring in my vehicle? Well YES you can… and that’s something
I’m going to look at right now. Stick with me if you’re interested.
Hi again guys… so firstly, are Piggyback fuse holders safe to use? Can you use them
to fuse tap – to safely connect electrical items in your vehicle? Yes. I believe so and
I cover those issues pretty fully in these videos.
This video will cover the safety implications of using the Piggyback incorrectly and overloading
your vehicle electrical system. For those of you not interested in seeing more of my
diagrams or listening to my electrical lectures, I’ll state nice and early that I personally
wouldn’t use a Piggyback to connect anything greater than 10 amps. If that what you want
to do, run a dedicated line. Anything less than 10 amps should be fine.
For the rest of you wanting to expand your understand of things a little, I’m about
to cover: So let’s get on with it.
What is an electrical overload? Well LOAD is the term applied to the amount of current
being drawn by an electrical device and is measured in Amps.
Wires that connect power to electrical devices (in vehicles or domestically) are rated by
the amount of load they can carry – how much current they can safely handle. The more
current a wire can carry, the thicker it is. This is simply due to the amount of conductive
material inside them. A thick wire can carry a small load with ease,
but being thicker it contains more copper, so it’s more expensive, plus it takes up
more room and is less flexible. Because of this vehicle manufacturers generally use as
thin a wire as they can get away with – to save money and make installation easier.
Now when you try to run a lot of current through a thin wire, the LOAD becomes greater than
the wire can handle and it OVERLOADS. This means it heats it. All wires heat up in use,
but it’s usually not something you can detect, but with an overload, the sheathing around
the wire can begin to melt. This can melt other nearby wires, short out against the
other devices or the chassis and, long story short, at best lead to electrical failures
and at worst create an electrical fire. So if you like, and overload is an electrical
disaster waiting to happen… In a vehicle fuse board, individual wires
typically connect to fuse holders. The thickness or gauge of the wire (ie the amount of load
it can take) is as low as the manufacturer can get away with. He doesn’t want to waste
money on thick wire and he knows that thin wire will overload. So it’s the Goldilocks
principle is you like, not too much, not too little, but just right.
Let’s say, for an example, that there’s a device that runs at a load of 17 amps. Then
a manufacturer would be stupid to run a wire rated only 11 amps to the device as it’s
simply going to overload. Similarly his shareholders would lynch him if he wasted money fitting
a 100 amp wire. So he’d probably fit a 25 amp wire… not too little and not too much…
just right. So how does all this fit in with the Piggyback
Fuse Holder? Well, I think by now you’ll probably be
beginning to see the possible implications for an overload using a Piggyback.
As I’ve demonstrated on my other videos, a Piggyback “shares” the wire that feeds
any given fuse within a fuse board. Whilst it does NOT affect the original fuse or even
the device that the original fuse is connected to, it does effect the wire that supplies
the fuse… it adds to the load. Let’s use an example. Let’s look at the
vehicle horn. This has a fuse to it, let’s say a 20 Amp fuse. If it’s a 20 Amp fuse,
the horn probably uses more than 15 Amps (which is a standard fuse size) so let’s guess
and say it uses 17 Amps. There has to be wire powering the fuse and
this has to be able to handle at least the same load as the fuse, otherwise it would
overload, and typical gauge with is 25 amps, so let’s say that… the wire can take 25
amps. When you use the horn, 17 amps of load passes
happily along the original wire, through the fuse and to the device. Great. Everything
works. Now along comes Mr Piggyback. Any power going
into the device powered by the Piggyback has to be drawn through the original wire.
So if we add another horn, why we’d do this I don’t know, but let’s say we did…
that means the original feed wire now has two 20 Amp fuses connected to it. Using both
horns will not affect the fuses in any way as both the original circuit and the piggyback
circuit operate independently, so you could be fooled into believing that all is well.
But it isn’t. If you used both horns at the same time, then
the chances are you’d be using far more load than the original cable can handle. The
overall load would be two lots of 17 which is 34 Amps. But our original feed wire is
only rated at 25 Amps… that’s an overload of 9 Amps and that’s more than enough to
lead to serious problems. Remember folks, when you see a car on fire, it might be nothing
to do with the fuel and everything to do with poorly fitted electrical auxiliary devices.
If I’ve terrified you there, well firstly good, you should be cautious of electricity,
it is dangerous, but secondly don’t be too concerned. Piggyback fuse holders can still
be used safely. At the beginning of this video you heard me
say that I wouldn’t recommend using a Piggyback to power anything of 10 Amps or more. It’s
a very general guide and I can’t be certain what’s happening in your vehicle… I’m
just making a very general guess. Certainly the lower the load, the safer.
Thankfully most vehicle auxiliary don’t use much power and that’s why the Piggyback
fuse holder can be safely sold and used. I first drew attention to piggyback fuse holders,
albeit indirectly, through my Hardwiring A Dashcam video. Now a dashcam is an ideal example
to use for a Piggyback. The Dashcam I fiited had an internal fuse
of 5 Amps if I remember correctly, so that means it probably runs at 3 or so Amps. So
let’s say 3 Amps. Using our Horn Circuit again, if we use the
Piggyback here and use a 10 Amp fuse or Lower, all will be well. Why you ask?
Well the horn load is 17 Amps. The Dashcam load is 3 Amps. That’s a total load of 20
Amps. As the original feed wire is rated at 25 Amps, we can see that there’s little
danger of overload here. Get the idea? As long as you’re not overly
taxing the original feed wire, as long as you are not increasing its load to a point
that the wire itself will fail, then you’re quite safe to use a Piggyback Fuse Holder
without the worry of Overload. And that’s a finished video folks.
I hope you found it helpful and I hope everything was nice and clear.
Please remember, I’m no expert, just a keen amateur, so it’s always worth checking out
some other videos on the subject and if you have any questions, drop me a line and I’ll
do my best to help. If you enjoyed watching this video, please
like it. If you didn’t like it, then why not let me know why. I’m always eager to
improve my videos. Your comments and questions are always welcomed
as I really love to hear from you so do drop me a message below. If you have a request
for a video tutorial, again drop me a line. I’ll help where I can.
Please do check out my YouTube channel and of course my other videos. I’ve got 50 plus
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interest from Subscribers, so thank you all for that, and if you haven’t subscribed
yet, please do. The more the merrier. So that’s it for now folks, and thanks very
much for watching.