# ALWAYS FUSE THE POSITIVE LEAD! Vote Please?



## teemyob (Nov 22, 2005)

Do you always follow the code of Fuse in the Positive line?

Reason I ask is that it I think in a lot of installations, you are more likely to short against an un-insulated/un-sleeved positive point of a Negative earth system.

http://www.emrg.ca/fuses.htm

What do you think?

TM


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## Penquin (Oct 15, 2007)

I fuse the positive so that in the event of a short it cuts the power supply, IMO you are more likely to touch a positive lead onto a negative part of the bodywork - that's my logic anyway......

Dave


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## Glandwr (Jun 12, 2006)

I do it because that is what those without a wiring diagram would expect.

Dick


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## GEMMY (Jun 19, 2006)

I leave it to the professionals, because I'm an electrical numpty and haven't a clue about what you're talking about. :? 

tony


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## teemyob (Nov 22, 2005)

*jobs*



GEMMY said:


> I leave it to the professionals, because I'm an electrical numpty and haven't a clue about what you're talking about. :?
> 
> tony


Horses for Courses I guess.

For some people some jobs are dead easy, funeral directors for instance.

TM


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## Glandwr (Jun 12, 2006)

GEMMY said:


> I leave it to the professionals, because I'm an electrical numpty and haven't a clue about what you're talking about. :?
> 
> tony


Not because you are a fan of Hillare Belloc Tony? 

_Lord Finchley tried to mend the Electric Light
himself. It struck him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisan._

Dick


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## GEMMY (Jun 19, 2006)

All for that Dick, spread it around if you can't do it yourself. :wink: 

Anybody want a new house built, I don't have to ask anyone.  

tony

Ps sorry for drifting off topic.


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## rosalan (Aug 24, 2009)

Assuming ground is negative on a vehicle, sometimes the only lead will be the positive, so I put a fuse in the available lead before the load. Then I short the circuit out and melt the wires :lol: 
Alan


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## erneboy (Feb 8, 2007)

Mira.


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## GEMMY (Jun 19, 2006)

Had to Google it Alan..... :lol: 

tony


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## teemyob (Nov 22, 2005)

*jist*



GEMMY said:


> Had to Google it Alan..... :lol:
> 
> tony


I got the jist of it....here is the translation

Here lies 
a good father 
a good husband 
a bad home electrician


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## teemyob (Nov 22, 2005)

*vote*

does this poll thing not work or are you not voting?


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## rayrecrok (Nov 21, 2008)

*Re: vote*



teemyob said:


> does this poll thing not work or are you not voting?


He he!  you have run out of electricians, you have only got us electrical numpties left.. (Blank look, I just turn stuff on and it works, if it don't I just give it a thump and then it does work).. :lol: :lol: :lol:

ray.


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## listerdiesel (Aug 3, 2012)

We have a multi-fuse fusebox which can be split into two sections. That gives us incoming supply fusing (charger, solar, external socket) and outgoing circuits for the lighting, kitchen/fridge and water heater controls.

The benefit of fusing is simply safety; you have to see an electrical fire with PVC cabling to appreciate how quickly it builds clouds of smoke which is toxic, in a confined space, plus the damage that red-hot wiring can do to fittings.

It also allows you to use smaller cabling which takes up less space.










That is an early shot of the trailer electrics, but you can see the fusebox in between the 240V board and the charger.

It's easier to do when you're building from new as we were, but there are smaller fuseboxes available for add-ons.

The fusebox we used is a RIPCA:

http://www.ripca.com/catalogus.php?toon=product&welke=889&template=-1

Peter


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## FoweyBoy (Dec 7, 2006)

I used a fuse block to make connections between my solar panel and the regulator and consequently fused both positive and negative. I assume this is acceptable practice, even if it is considered unnecessary to fuse both. :?:


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## teemyob (Nov 22, 2005)

*neat*



listerdiesel said:


> We have a multi-fuse fusebox which can be split into two sections. That gives us incoming supply fusing (charger, solar, external socket) and outgoing circuits for the lighting, kitchen/fridge and water heater controls.
> 
> The benefit of fusing is simply safety; you have to see an electrical fire with PVC cabling to appreciate how quickly it builds clouds of smoke which is toxic, in a confined space, plus the damage that red-hot wiring can do to fittings.
> 
> ...


neat job!


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## User1 (Apr 13, 2012)

Bit like domestic electricity only difference is it don't hurt as much. If the fuse blows then the device it protects is not live and cannot short itself out and set itself on fire. If a motor burns itself out and the windings short to the casing then the fuse blows. If the fuse is on the negative side then the motor would draw to much current and the fuse would blow providing the wiring could stand it but the motor would still have live windings and if they shorted to the casing then there would not be a fuse in the circuit and you may well have a fire. So always protect the side where the power comes from. Or the lead that is more positive than the other. Electricity always flows from the lead that has a higher potential than the other.



FoweyBoy said:


> I used a fuse block to make connections between my solar panel and the regulator and consequently fused both positive and negative. I assume this is acceptable practice, even if it is considered unnecessary to fuse both. :?:


Thats wrong. Depends on fuse tolerances. The wrong fuse may blow and leave the unit live. You only need one fuse. Not that you are going to suffer a fatal shock from a solar panel ....


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## listerdiesel (Aug 3, 2012)

*Re: neat*



teemyob said:


> neat job!


Cheers, we did have a lot of wall space!

I'll get an up to date picture when I've done the changes we have planned.

Peter


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## FoweyBoy (Dec 7, 2006)

FoweyBoy said:


> I used a fuse block to make connections between my solar panel and the regulator and consequently fused both positive and negative. I assume this is acceptable practice, even if it is considered unnecessary to fuse both. :?:


Thats wrong. Depends on fuse tolerances. The wrong fuse may blow and leave the unit live. You only need one fuse. Not that you are going to suffer a fatal shock from a solar panel ....[/quote]

Thanks User1. That is a good point I had not considered. So if I put a lower rated fuse on the positive, compared to the negative, then the positive fuse should blow first :?:


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## pippin (Nov 15, 2007)

If the negative side is sort of at chassis potential, as it should be in a vehicle, and the appliance has a direct connection to chassis that is not shared by anything else then there is no need to fuse the negative lead of 12V systems.

In a 12V DC system it doesn't really matter and just complicates things.

In the UK we do not have fuses in the neutrals of our AC mains wiring - the neutrals are tied (roughly) to earth.

Yes, there are (very, very) unlikely instances where a negative or neutral can carry high currents under (very, very) rare fault conditions.

With UK mains stuff NEVER EVER fuse the neutral side.

In countries where neither side of the AC mains is tied to earth then it is necessary that both sides are "fused" but not by fuses.
They should be protected by an overload current trip in both wires that simultaneously breaks both connections.
(ditto for earth leakage trips)

Incidentally, the accepted maximum voltage that is not fatal is 55V (very much simplified statement).

The open circuit voltage of a solar panel can head upwards towards that so you can get a bit of a belt.
It wouldn't kill you directly but you might react instinctively and fall off the roof of your van!!!!


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## aultymer (Jun 20, 2006)

Where on earth did the idea of fusing the neg side on 12volt systems come from?


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## bigcats30 (Aug 13, 2012)

aultymer said:


> Where on earth did the idea of fusing the neg side on 12volt systems come from?


it's called over kill

Even a 230V house system isn't twin fused...yet for some reason people feel the need to do it to a 12v system that can just manage to power a lightbulb (on a sunny day).


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## aultymer (Jun 20, 2006)

> it's called over kill


It should be called people kill. 12volt won't kill you but the fire might.


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## brianamelia (Mar 17, 2008)

*reply*

I have seen many crimes on vehicles where people have tried DIY installs.Dont forget you have to find a live to connect to in the first place and there the troubles can start.Unless you are competent with electrical testing equipment,certain test lights etc etc be careful.
Bra


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## ched999uk (Jan 31, 2011)

bigcats30 said:


> aultymer said:
> 
> 
> > Where on earth did the idea of fusing the neg side on 12volt systems come from?
> ...


You are not quite right there. Modern domestic electrics require earth leakage trips. These disconnect both Live and Neutral in the event of a fault!!

But in my opinion fusing +12v and negative is over kill. Remember that the cable that goes between starter motor to battery and the one from battery to alternator doesn't very often have a fuse!!!

For the little cost of a fuse it's always worth it. I have experienced an in car electrical fire due to no fuse. If I had not had a fire extinguisher and wire cutters in car it would have gone up in lots of smoke!!!


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## raynipper (Aug 4, 2008)

I'm surprised this thread has gone on this long?????

Ray.


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## aultymer (Jun 20, 2006)

> For the little cost of a fuse it's always worth it. I have experienced an in car electrical fire due to no fuse. If I had not had a fire extinguisher and wire cutters in car it would have gone up in lots of smoke!!!


 No one has suggested that you should not fuse the positive side.


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## brianamelia (Mar 17, 2008)

*reply*



aultymer said:


> > For the little cost of a fuse it's always worth it. I have experienced an in car electrical fire due to no fuse. If I had not had a fire extinguisher and wire cutters in car it would have gone up in lots of smoke!!!
> 
> 
> No one has suggested that you should not fuse the positive side.


Not sure thats the case 10% of people on the vote have suggested so
Bri


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## pippin (Nov 15, 2007)

I re*fuse* to post on this topic any more.

Anyway, the original poll is flawed but I'll let you lot work out why.


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## aultymer (Jun 20, 2006)

> Not sure thats the case 10% of people on the vote have suggested so
> Bri


Only Darwin award candidates.


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