I'm wiring a dashcam this weekend, so I've bought a fuse tap, 12v socket etc. The 12v socket has two wires, red and white (I can't find an electrical colour code that uses those colours )

I've assumed the red wire is live so I've crimped that into the fuse tap. I'm not sure what to do with the white wire -- should I attach the white wire to some unpainted metal as neutral/ground? Has anyone come across these colours before?

They are usually red/black.

Attach the white one to any body mounted bolt/screw for earth.

When fitting the fusetap make sure you don't put the top fuse in until you have checked that you have the tap in the right way round.

Put the tap in, check that there is no power to the device then put the fuse in and it should power up.

If you get power without a fuse then turn the tap around and all will be ok.

(If it powers up without a fuse in then the fuse is being bypassed and the circuit will have no protection- risk of fire if something surges) .

I can't speak for chinese quality stuff but surely in a good quality fuse tap the secondardy circuit output should be isolated until a fuse is put in, regardless of what way round the fuse tap is fitted? If the fuse tap could be put in the wrong way and both circuits become live without a fuse or with one fuse fitted both become live then this is quite dangerous.

I will make a quick sketch of how I would take a quality fuse tap to be configured.

The circuit is isolated if inserted the right way round.

If in the wrong way round it isn't.

All configured :)

No current when fuse disconnected, no current when ignition off (tapped front windscreen wiper fuse), no current when neutral disconnected from chassis.

Dashcam footage seems OK (using the epance mini 805)

This is how I would expect a fuse tap to be configured. It's fool proof as both circuits would need a fuse in place regardless of what way round the feed and load are. The only difference if they are reversed is that the second circuit would be fed through the primary fuse.

The problem is that you are assuming that the terminals are positive and earth, that is not the case.

All fuse terminals are positive, the earth link comes after the device connected.

As the 2 terminals opposite the fusetap wire are linked if you put the wire to the wrong side of the fuse it will become an unprotected live feed.

Technically it is protected via the bottom fuse but you will be pulling a double load through one fuse which is unsafe and has caused fires in cars.

That is why the majority of Motor Factors shops have stopped selling them, unknowledgeable people fitting them the wrong way round and wondering why their car is smelling of smoke.

Forewarned is forearmed.

I am not assuming there is any positiive 'and' earth - hence feed and load. There is no earth in my diagram, its all positive terminals. As a time served spark I would be quite concerned if I was.

Given that fuse taps are prewired with a bit of feed, they cannot be connected into the wrong side and then unprotected.

pulling both loads through one fuse is much safer than potentially (guess work to the average punter) having no circuit protection what so ever.

A tap should be considered an addition to an existing circuit, hence the name most likely. so worst case scenario with the tap the wrong way round and both circuits going through one fuse is a bit like the following:-

For example, in a domestic ring main rated at 32A we can take a spur or in this case a tap, but we dont alter the existing circuit - its simply an addition to it. So in the case of a ring circuit you are adding a point which potentially draws 13A of the available 32A, Some consideration to determine the load and suitability otherwise it will trip or blow the fuse. The same pretty much applies for a fuse tap.

The point of 2 fuses is because there is likely to be something requiring a lower/higher ampereage parasitically feeding off another circuit.

If you only have one fuse then it is unlikely to be matched to the parasitic load and therefore at risk of overloading.

It would be like running plugs from a domestic outlet with the fuse removed and a wire soldered in.

Yes you have the main breakers in the fusebox but the item plugged in is likely to overload in the case of a fault.

It's all about safety, even you can't argue with that.

Would you put a 13A fuse into the plug connected to a 3A device?

Took you a while to google that did it ??

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In the case of my diagram, no circuit can operate without its fuse being in place - so perfectly safe.

IF the fuses were to be inserted in the wrong places, a 20A for original circuit and a 10A for the new circuit, the worst thing to come from it would be a blown 10A fuse.

And regarding a 13A fuse for a device drawing 3A - doesn't mean much as for arguement sake, a soldering iron rated at 100W @110v will draw 0.9A, but its fused at 16A if used in commercial/industry.

Took you a while to google that did it ??

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No google involved, just good old common sense.

In the case of my diagram, no circuit can operate without its fuse being in place - so perfectly safe.

And regarding a 13A fuse for a device drawing 3A - doesn't mean much as for arguement sake, a soldering iron rated at 100W @110v will draw 0.9A, but its fused at 16A if used in commercial/industry.

So you'd quite happily recommend fitting 13A fuses in all plugs?

I think I'll stick to my guns on this one.

He may be one of those geeks tho paisleyjim

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So you'd quite happily recommend fitting 13A fuses in all plugs?

I think I'll stick to my guns on this one.

I haven't at all said that.

Draw me a diagram of how you deem a fuse tap to function?

Common sense if you have 1 a trade in electrics or 2 read it up ..I for one have no knowledge of car or any electrics so I think I will go with the guy who has a trade in it

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Anyway, we're talking cars (and at a tangent domestic appliances) not industrial equipment.

If fusetaps are 'safe' with one fuse why fit them with two then?

Because electrical principles are exactly the same where ever you apply them.

There are 2 fuses because it creates an additional spur for a circuit. The original circuit still needs a fuse and the additional circuit (which should be of lesser rating) needs a fuse to protect it also.

Boo ya. Take that

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let's see how you would deem a fuse tap to be configured?

He's trying to find one on google too

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There are 2 fuses because it creates an additional spur for a circuit. The original circuit still needs a fuse and the additional circuit (which should be of lesser rating) needs a fuse to protect it also.

That's my exact point.

If you put a fusetap in the wrong way round then the secondary fuse is bypassed.

You proved my argument for me there.

Ta!

That's my exact point.

If you put a fusetap in the wrong way round then the secondary fuse is bypassed.

You proved my argument for me there.

Ta!

If you put it in the wrong way round in the diagram I posted, then the second fuse is NOT bypassed. It should be of lesser rating as its a tap so there for still adequately protected and safe.

So no, I have proved your point wrong.

Take a look at this diagram, the top one shows the fuse tap inserted into the fuse box in the preffered orientation, the bottom one shows what happens if you insert it the wrong way round.

Both circuits still fuse protected but in the case of the wrong orientation if you loose the primary circuit fuse then you loose the second one too.

simple and safe.

when i get it loaded up