Installing of fuse box in engine compartment

[Hyun]

i bought my fuse box (that little box with voltmeter reading, 150A fuse) from simp limp tower, and brought it during my install to Mok of bukit timah. he installed everything else except the fuse box. he didn't consider that basic install, and said it required using metal brackets to secure it near the battery terminal, that since i didn't buy from him he wont install it.

 

i suppose that's reasonable, not sure what u think. so now i'm left with this fuse box. if i dont use it, my circuit has no fuse. although the fuse is a little large for my amp - my single amp supposed to use 120A but i couldn't find 120A... either 150A or smaller A. i guess if next time i add a 2nd amp, a 150A maybe just nice - 120A to this amp, 30A to the other amp.

 

so i attached my fuse box temporarily to the other end of the power input cable - in the boot, just before my amp. technically it's on the same line in the circuit diagram - the positive input, although the positioning has changed - instead of being next to battery + terminal, it's now at tail end of the same wire.

 

therefore technically it's serving the same purpose. but is it wrong in any way? why do people always install it in the engine compartment?

[Bosebani]

Mok of Koncept Audio???

[Kwongwing]

Not everyone installs the fuse box in the engine compartment. Mine is at the back, just before the split to the various amps.

So long as the fuse block is positioned before the components/equipment it is meant to protect, it should be fine

[Maded]

i think ppl install in the front coz, in the event of a collision and a short circuit, the fuse will break and prevent high currents from going into the rear of the car (or the passenger compartment) where it could start a fire....

[Hyun]

yes, Koncept. for a while i forgot his shop name.

 

i'm not familiar with how electricity works. in fact, electronics leave the battery from the NEGATIVE terminal, and not the positive. so in the event of this said collision etc, i really wonder whether the position of the fuse box actually limits the extent whereby the electricity can do damage. anyone can put a finger of certainty into this?

[Headshok]

acutually,you are correct on the point where electricity works on the basis from negative to positive.

 

i am damm rusty on this ( let me look thru my text book), but if i remember correctly, electron flow is from negative to positive, conventional flow is from positive to negative, thus i think in the case of ICE, we base it on conventional flow(positive to negative), let me go dig up more info on this..i may have got my info wrong, let me go look thru again.

 

IMHO, pple put the fuse box near the battery so that should anything happen, the surge is as far away from their amps as possible. if lets say one day ur alternator ki siao and battery also ki siao, ur fuse blow and ur cables start to melt, at least ur fuse box is far away from ur amps. but if u put ur fuse box next to ur amp, its more "dangerous" in a way..

 

but most kiasu pple (inclusive of me), put 1 fuse box at the battery and one more fuse distribution blk just b4 the amps.. heheh.. machaim usin double condom..l hahaha

[Kermit]

Has anyone considered that the fuse box is near the battery to protect the battery and engine compartment, and not necessarily the amps?

 

Like what Headshok has, I also use double condoms...One fuse block near the battery and one fused distributor block near the amps.

 

Hyun - btw, the thing you have does sound like a capacitor to me...since got voltmeter.

Edited February 21, 2006 by Kermit

[Headshok]

some of the fuses got the volt meter one.. heheh..

 

damm, any phys teacher here? can clarify btw conventional flow and electron flow? there is a difference btw the 2.. i cant find the damm thing in my text book.

there are some cases where u use electron flow instead of conventional flow, but i doubt in this case..

[Silver_z]

Was installing my friend's capacitor some time back. The installation manual specifically state that a fuse must be installed between the battery and the capacitor. And that the lenght of cable from battery to the fuse should not be longer than 8". Not sure why, I think there is a reason why fuse are installed near the battery.

[Headshok]

here's something i found online abt the 2 different types of flows:

 

"In conventional flow notation, we show the motion of charge according to the (technically incorrect) labels of + and -. This way the labels make sense, but the direction of charge flow is incorrect. In electron flow notation, we follow the actual motion of electrons in the circuit, but the + and - labels seem backward. Does it matter, really, how we designate charge flow in a circuit? Not really, so long as we're consistent in the use of our symbols. You may follow an imagined direction of current (conventional flow) or the actual (electron flow) with equal success insofar as circuit analysis is concerned. Concepts of voltage, current, resistance, continuity, and even mathematical treatments such as Ohm's Law (chapter 2) and Kirchhoff's Laws (chapter 6) remain just as valid with either style of notation.

 

You will find conventional flow notation followed by most electrical engineers, and illustrated in most engineering textbooks. Electron flow is most often seen in introductory textbooks (this one included) and in the writings of professional scientists, especially solid-state physicists who are concerned with the actual motion of electrons in substances. These preferences are cultural, in the sense that certain groups of people have found it advantageous to envision electric current motion in certain ways. Being that most analyses of electric circuits do not depend on a technically accurate depiction of charge flow, the choice between conventional flow notation and electron flow notation is arbitrary . . . almost.

 

Many electrical devices tolerate real currents of either direction with no difference in operation. Incandescent lamps (the type utilizing a thin metal filament that glows white-hot with sufficient current), for example, produce light with equal efficiency regardless of current direction. They even function well on alternating current (AC), where the direction changes rapidly over time. Conductors and switches operate irrespective of current direction, as well. The technical term for this irrelevance of charge flow is nonpolarization. We could say then, that incandescent lamps, switches, and wires are nonpolarized components. Conversely, any device that functions differently on currents of different direction would be called a polarized device. "

 

i tink we should follow the conventional flow instead of electron flow in ICE.. if we follow electron flow, all our setups all wrong liao.. hahaha

[Headshok]

yoyo,

 

accordin to IASCA standard, the fuse from the battery must also be a certain lenght also.. heheh..

 

aiyah.. best to just double condom lah.. haha.. safe than sorry lor..

[Wankie]

use double condom can still feel anything meh? ok ok, OT ... aiya all you ppl ah, do things until so complicated one. keep everything simple simple install once don't touch liao then no issue liao rite kekeke.....

[Headshok]

go commando lor.. hahah

 

aniway, just sayin, just put one big fuse in front, put a fuse dist blk behind, enough liao.. heheheh

[Silver_z]

That's my setup too. haha...

[Darkness]

U are correct bro...my amp manual recommend that the fuse be placed within 8" of the battery.

[Wankie]

eh you been spying on me ah

[Hyun]

in what cases do fuses blow?

 

have any of u experienced this alternator or battery ki siao phenomena?

 

or when u turn the amp gain up too high, it draws too much current and exceeds the rating of the fuse?

 

have u ever heard of fires starting?

 

or are these all conspiracy theories?

[Darkness]

Currently I myself am doing some rewiring so this issue of fuses is very relevant to me.

 

I would like to share some of the info i have gathered so far. (If wrong pls correct me, if redundunt pls ignore me).

 

Source: http://www.bcae1.com/fuses.htm

(It is very detailed and a must read esp for a newbie like myself)

 

Some of the more important issues: (Those in blue are quoted from the site)

 

Why a Fuse in the first place?

 

Function:

A fuse is generally inserted into an electrical circuit for 1 of 2 reasons, either to protect the power source which includes the wire that connects the power supply to the electrical device, or to protect the electronic equipment. The electronic equipment manufacturers specify a fuse rated to open the electrical circuit before damage can be done to the device or open the circuit if the electronic device fails in some way (electronic devices may pull excessive current when they fail). If a fuse larger than the specified fuse is used, a small mistake when installing the equipment may cause catastrophic failure of the equipment. WHEN, not if, WHEN you're thinking of replacing a blown fuse with a higher rated fuse ask yourself if you know more than the engineer who designed the equipment. Don't get in a hurry when installing electronic equipment. Take the time to go get the right fuse. 50 cents for a fuse is better than $50 labor plus the cost of the replacement parts for a repair job.

 

Table 1:

 

Wire Gauge Recommended

-----------Maximum

-----------Fuse Size

----------------------

00 awg-----400 amps

-0 awg-----325 amps

-1 awg-----250 amps

-2 awg-----200 amps

-4 awg-----25 amps

-6 awg-----80 amps

-8 awg-----50 amps

10 awg-----30 amps

12 awg-----20 amps

14 awg-----15 amps

16 awg-----7.5 amps

 

These are the recommended maximum fuse ratings for the corresponding wire size.

Using a smaller fuse than what's recommended will be perfectly safe.

 

And Hyun to paritally answer ur query on does the fuse actually real blow:

 

Fuse Opening Time:

 

A fuse does not blow when the current reaches its rated current. It is designed to pass its rated current without opening. A fuse will take varying times to blow under different conditions. A fuse will pass significantly more than its rated current for a very short time. It may take 10 minutes or more to blow a fuse at 25% over its rated current. The table below is an example of the specifications for a slow blow fuse. You can see that a 20 amp fuse may pass 40 amps of current for as long as 5 minutes before blowing although it probably wouldn't take a full 5 minutes to blow. The times for other fuses will be slightly different.

 

Table 2:

 

%of amp rating Opening time

110%---------- 4 hours minimum

135%---------- 1 hour maximum

200%---------- 5 minutes maximum

 

and abt fire hazard in the vehical:

 

Wire "D" is a smaller wire. It's also supplied power by the dblock. Since this wire is smaller (let's say an 8g wire), the main fuse can not protect against a short circuit. If the 8g wire shorts to ground, it will burn (and possibly take the vehicle with it). This would be a very unsafe condition. (u might need to refer to the website for the diagram)

 

So i guess it is when these "unprotected" wires melt or burn that a fire hazard occurs. That is why they say that the wire from the batt to the fuse must be less than 8"...less wire is unprotected thus less combustible material i guess.

 

Poor Quality AGU fuses:

 

The biggest problem with the AGU fuse is the quality. I am NOT saying that there are no good quality AGU fuses but there are a large number of manufacturers that make fuses of questionable quality. The lower quality fuses have a problem with the solder that connects the end caps to the fusible element. There is too much resistance in the solder connection which (with current flow close to their rated current) creates enough heat to melt the solder connection which leads to a melted fuse holder or a fuse with higher than normal resistance. The higher resistance will cause more of a voltage drop than a new fuse. If you can find some BUSS or LITTELFUSE brand AGU fuses, you won't be as likely to have problems. All of these problems can be alleviated by using Maxi fuses in the first place.

 

Some observation / irony abt these info and commercial products

 

Observation / Irony 1: But a quick check with fellow ICE fanatics and few shops tells me that for example a 4 guage in 4 guage out anl fuse holder comes with a 150A fuse (the default one). Why not a <125A fuse based on table 1?

 

Observation / Irony 2: I notice most amps (atleast those i have) have their own maxi fuses. So am i correct to say that the additional fuses we add to the distribution block etc are to protect the wire bet the distribution block and the amp and not the amp itself?

 

Lastly: Are there and distribution fuse holders with maxi fuses instead of AGU fuses?

 

Thanks.

 

Once again i know this is rather trivial and perhaps even irrelevent to this thread but i just tot that newbies like myself are better off knowing such information since elecronics and its associated hazards are rather real esp so in a "self designed" system.