• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Yet another Fusible link question.

MS03 2500

PM 2017
PM 2015
SM 2014
PM 2013
PM 2012
SM 2011
SM 2010
SM 2009
SM 2008
SM 2007
SM 2006
Full Member
Joined
Oct 17, 2005
Messages
39,235
Location
Lexington KY
While I have the AV apart putting in new electrical veins (AKA) Wiring upgrade. I'm debating about what to do about the Fusible link. I'm going with a 250 amp alternator and I really want a fuse between the alternator and the accessory box.  Would using 2 fusible links work OK.

I am also putting in 2 500 watt fan motors 
 

Attachments

  • wat.GIF
    wat.GIF
    41.1 KB · Views: 79
I just bouncing it off everyone I really don't want to leave it unfused for fear of fire.

Yeah Sperry would have said you need more batteries >:D
 
OEM uses fusible links because they are cheap and simplistic. Realistically all they are is a wire of a lesser gauge designed to blow like a fuse would. Personally since you are likely going to upgrade your wiring to carry the extra juice I would just install a fuse at the battery and maybe one at the alternator. You can pick up decent inline fuses that won't affect your power carrying capacity.

Otherwise no reason why you couldn't use multiple fusible links but just be aware they all must be the same size, length and should be the same manufacturer etc to insure the resistance across them all are the same to insure the shared load really is shared equally.  Would still be better to use just one but if your paying attention to what your doing it shouldn't be a major issue.

 
I would absolutely not wire them in parallel for additional amperage capacity.
 
enoniam said:
I would absolutely not wire them in parallel for additional amperage capacity.
Ditto... as more then likely you would not get your full ampacity of the system since one would blow before the other and then the other would blow instantly after
 
B, I'm assuming you are referring to an actual fusible link and not an inline fuse, as many people use them as synonyms and refer to in-lines and fusible links as well, but they are different. Using multiple fusible links can be a PIA, especially if you are trying to run them in parallel, or if one is consumed, because as Rod noted, that they all need to be identical to function properly. if you go this route, buy some spares at the onset of your project so you have them on hand if ever needed. There's a reason manufacturers use them, and Rod pointed it out, they're cheap. Using them would certainly work, but I personally am a fan of breakers as opposed to fusing and definitely over fusible links. To Comply with competition rules, I had to (would have anyway) have a circuit interrupter (fusible link, fuse or breaker) between each alternator and battery, and within 24" (this really should be more like 12') of any feed larger than 10 Ga. leaving any one of the batteries. For this reason, there are 5 Breakers in my system.
Some people like fuses so that they can run an oversize wire ga. but limit the amount of amperage through it to "protect" their equipment and will add larger and larger fuses as they add accessories, but the fuse or breakers primary function at this location should not be to protect your equipment, but to, exactly as you mentioned, protect the vehicle from damage or a fire in case of a dead short between the alt and battery, and battery and the rest of the vehicle.  Because of this, the breaker/fuse should be sized for the ga. and power handling of the wire, not of the accessories attached to it.
hope this helps.
 
ygmn said:
Ditto... as more then likely you would not get your full ampacity of the system since one would blow before the other and then the other would blow instantly after
enoniam said:
I would absolutely not wire them in parallel for additional amperage capacity.

you guys are sneaky, you both commented as I was typing
 
Yes I was referring to this one. So you guys don't think I should run 2 from the generator to the red box. I do understand if one blows the other will blow also that's what I would want it to do. I figured if I could push 145 amps through one I should be good to 290 with 2.

Calicak89 can you post a link to the circuit interrupter you have.

0603161522_zpsnrhlgbbf.jpg
 
It's highly unlikely that each leg of the parallel circuit, the fusible links plus each's associated wiring to the junctions, will have the same resistance and hence the same current.  Therefore you can't just double what each one is capable of.

Your goal will be to have minimal resistance through each leg.  Below 1 ohm through each leg a very minor absolute difference in resistance becomes huge in proportion.  You may well have twice or more current going through one leg over the other.  Hence two 145 amp fusible links may be barely able to support 200 amps.
 
I have a 225 amp alt and I'm running a single 250amp Mega Fuse with a 1/0 cable directly from the alt to the battery.  I got this from Wrangler way back when I upgrade the alternator.. You can get them on ebay or other electrical supply stores or marine.. Then ditch the factory fuse-able link..

With a 250 amp alternator you probably want to run a 300 amp fuse..

Also make sure you run a new/additional ground as close to the alternator as possible or if the new alternator has a ground stud then attach it there and then to the battery negative.

http://www.ebay.com/itm/Littelfuse-02981001ZXT-Fuse-Block-Fuse-Holder-for-AMG-High-AMP-Fuses-MEGA-Fuse-/271841753768?hash=item3f4b07faa8:g:fBgAAOSwNSxVMWql
 

Attachments

  • Mega Fuse 1.jpg
    Mega Fuse 1.jpg
    85.8 KB · Views: 59
  • Mega Fuse 2.jpg
    Mega Fuse 2.jpg
    90.1 KB · Views: 61
Thanks Randy that looks simple enough.
 
Run the Fuse size based on your wire size.
Fuses are there to protect the wire.

Per my handy NEC cheat book (national Electric Code)
Allowable ampacity of 90C rated Single THHN 9other) wire in open wire
1/0 Awg = 205A
2/0 Awg = 235A
3/0 Awg = 275A
4/0 Awg = 315A
250 Kcmil = 355A
300 Kcmil = 395A

So for each rating above you need to fuse them @ or below the allowable ampacity to prevent the wire from ruining your day.

Note by code:
14 Awg wire is to be protected by 15A
12 Awg by 20A
10 Awg by 30A
Check your house wiring!

FYI
3 conductors together in open air are rated as:
1/0 Awg = 135A
2/0 Awg = 150A
3/0 Awg = 175A
4/0 Awg = 205A
250 Kcmil = 230A
300 Kcmil = 255A



 
This is where I go when I'm looking for wire sizing and wiring help..


http://www.the12volt.com/wiring/recwirsz.asp


http://www.the12volt.com/
 
Here are the breakers I run.
http://stingerelectronics.com/catalog/power/SGP90200
that links to their 200A, but they make them in various sizes from 50A upto 300A.
don't buy them direct, you can get them way cheaper from 3rd party vendors
set up just like randy, but used breakers instead of Megas like he did
 
Randy said:
This is where I go when I'm looking for wire sizing and wiring help..


http://www.the12volt.com/wiring/recwirsz.asp


http://www.the12volt.com/
but what is all that based on?

I mean it is crazy to put 60 amps thru 10awg wire

the National Electric code which is written by the NFPA (national Fire Protection Agency) limits 10 awg to 30A

I wonder what SAE says?

I know ABS and other ship building rules default to NEC or IEC rules.
So I cannot see cars be special.

Just my 2 cents to keep people safe
 
Actually most manufacturers say silly stuff like that what they do not state it's if not longer than 4 feet. I'm using the XS Flex 1/0 they state I can have 1345 AMP up to 5 feet even thou they supply a 350 amp fuse.

XS Flex is that 100% OFC cable the XP flex is a CCA cable
 

Attachments

  • xspowerchart.GIF
    xspowerchart.GIF
    53.2 KB · Views: 42
CRAZY.... and SCarry to me...

 
Absolutely, sometimes you have to use commons sense. I had too many bad experiences with melted wires.
 
ygmn said:
but what is all that based on?

I mean it is crazy to put 60 amps thru 10awg wire

the National Electric code which is written by the NFPA (national Fire Protection Agency) limits 10 awg to 30A

I wonder what SAE says?

I know ABS and other ship building rules default to NEC or IEC rules.
So I cannot see cars be special.

Just my 2 cents to keep people safe

Actually you have to pay attention to what NFPA is talking about... They generally are rating the wires for 120 volts not 12... When I looked up wire size capacities a few months back I had to go to a site like 12volt.com to get a reasonable wire/amperage design because the wiring at 12 volts is much different from 120.

So it is important to note the voltage to go along with that amperage to see what size breaker/fuse you need. Generally they are also rated for voltage and amperage.
 
redheadedrod said:
Actually you have to pay attention to what NFPA is talking about... They generally are rating the wires for 120 volts not 12... When I looked up wire size capacities a few months back I had to go to a site like 12volt.com to get a reasonable wire/amperage design because the wiring at 12 volts is much different from 120.

So it is important to note the voltage to go along with that amperage to see what size breaker/fuse you need. Generally they are also rated for voltage and amperage.

amps are amps...

NEC is COde for allowable ampacity I listed above is for 0-2000V single conductor in free air which is the highest rating they allow.

only way to get more is special wire and insulation that can handle more temps - like wires used in OVENS and RTDs.

I am just wondering who made that list and what Specification it is based on as I could not find anything in the foot note.

 
redheadedrod said:
Amps are amps, but volts are volts and volts*amps = wattage or power.

It DOES make a difference... 

....

All I can say is that volts do not effect ampacity of wires per NEC and other electric codes.

The voltage a wire can carry is based on the insulation so it does not shoot out insulation.

Read the NEC code as I have stated the ratings I gave are based on 0 to 2000V.
That covers your 12v and any higher volatge up to 2000V

so I ask what did that website base its ampacity on?

 
Back
Top