Fusible Links
02-10-2006, 10:00 AM
#1
Le Mans Master
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Fusible Links
Arn't fusible links nothing more than a wire that is approx. 4 steps smaller than the gauge wire in the circuit? Like a 10ga wire circuit would have a fusible link wire of 14ga?
Also, can any EE gurus answer how you determine the length of the fusible link??
Also, can any EE gurus answer how you determine the length of the fusible link??
02-10-2006, 10:35 AM
#2
Originally Posted by GRX
Arn't fusible links nothing more than a wire that is approx. 4 steps smaller than the gauge wire in the circuit? Like a 10ga wire circuit would have a fusible link wire of 14ga?
Also, can any EE gurus answer how you determine the length of the fusible link??
Also, can any EE gurus answer how you determine the length of the fusible link??
02-10-2006, 10:49 AM
#3
Le Mans Master
NAPA BELDEN Catalog 25524
The information notes that the jacket insulation of fusible link wire is
made out of cross-linked polyethylene (SXL grade). The idea being
that this kind of insulation stands a better chance of remaining intact
after the copper wire burns and separates - keeps the 'hot' end of the
wire from shorting out against nearby grounds.
It goes on to mention that SAE tests use a charged 500-600A battery
and a 6-inch piece of fusible link spliced into a 15-foot length of 4 gauge
sizes larger numerically/smaller physically primary wire. Both ends
are attached to the battery. All fusible links should short out in ten
seconds or less, regardless of the gauge. (They warn that because of
the dangers, don't try this in the field.)
The '89 Helms FSM says there are two kinds of fusible links: Silicon GXL
(GXL is thinner insulation than SXL, TXL is thinnest) and Hypalon. It
says to replace Hypalon with Hypalon. It also says never to make a
fusible link longer than 9" if cutting from a spool of material.
.
Fusible Link Wire FAQ (pg 29)
What's the CONDUCTOR made out of in a fusible link wire?
The conductor in a fusible link wire is the same as regular primary wire
(copper). IT IS NOT A LOW-MELTING-POINT COPPER CONDUCTOR.
It IS approximately four wire gauge sizes smaller than the circuit wire
leading up to it. Example: a 12 gauge circuit wire would normally require
a 16 gauge fusible link wire.
How do I know what GAUGE SIZE and LENGTH fusible link wire to use?
{First it says 'Use the same size/length as the OEM did'} Usually,
a fusible link wire will be approximately 9 inches or less and is four wire
gauge sizes smaller than the circuit wire leading to it.
Bold and caps emphasis shown above is as appears in the catalog.What's the CONDUCTOR made out of in a fusible link wire?
The conductor in a fusible link wire is the same as regular primary wire
(copper). IT IS NOT A LOW-MELTING-POINT COPPER CONDUCTOR.
It IS approximately four wire gauge sizes smaller than the circuit wire
leading up to it. Example: a 12 gauge circuit wire would normally require
a 16 gauge fusible link wire.
How do I know what GAUGE SIZE and LENGTH fusible link wire to use?
{First it says 'Use the same size/length as the OEM did'} Usually,
a fusible link wire will be approximately 9 inches or less and is four wire
gauge sizes smaller than the circuit wire leading to it.
The information notes that the jacket insulation of fusible link wire is
made out of cross-linked polyethylene (SXL grade). The idea being
that this kind of insulation stands a better chance of remaining intact
after the copper wire burns and separates - keeps the 'hot' end of the
wire from shorting out against nearby grounds.
It goes on to mention that SAE tests use a charged 500-600A battery
and a 6-inch piece of fusible link spliced into a 15-foot length of 4 gauge
sizes larger numerically/smaller physically primary wire. Both ends
are attached to the battery. All fusible links should short out in ten
seconds or less, regardless of the gauge. (They warn that because of
the dangers, don't try this in the field.)
The '89 Helms FSM says there are two kinds of fusible links: Silicon GXL
(GXL is thinner insulation than SXL, TXL is thinnest) and Hypalon. It
says to replace Hypalon with Hypalon. It also says never to make a
fusible link longer than 9" if cutting from a spool of material.
.
Last edited by Slalom4me; 02-10-2006 at 12:49 PM. Reason: Changed 21 gauge to read 12 gauge - thanks, kalister1
02-10-2006, 10:49 AM
#4
Burning Brakes
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You are correct with the sizing of the fusible link. They are typically 4 sizes smaller in gauge than the wire used on the circuit.
The fusible links are softer because the insulating material is softer and more pliable. I am not sure if the metal is a different type / alloy or not.
As for the length, I would suggest 5" - 6" maximum.
Good luck,
Dino
The fusible links are softer because the insulating material is softer and more pliable. I am not sure if the metal is a different type / alloy or not.
As for the length, I would suggest 5" - 6" maximum.
Good luck,
Dino
02-10-2006, 12:36 PM
#5
Drifting
Originally Posted by Slalom4me
] approximately four wire gauge sizes smaller than the circuit wire leading up to it. Example: a 21 gauge circuit wire would normally require a 16 gauge fusible link wire.
.
.
02-10-2006, 12:45 PM
#6
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Originally Posted by kalister1
You have that backwards, 16 gauge wire is larger than 20. I have not heard of odd gauge numbers either?
02-10-2006, 12:46 PM
#7
Le Mans Master
Originally Posted by kalister1
You have that backwards, 16 gauge wire is larger than 20.
I have not heard of odd gauge numbers either?
I have not heard of odd gauge numbers either?
.
02-10-2006, 01:38 PM
#8
Drifting
Yes that looks lot's better. I have worked in the defense electronics industry for close to 30 years and have never used an odd gauge wire. I will not disput that they exist, I have never seen them spec'd out for use.
02-11-2006, 02:52 PM
#10
Le Mans Master
The fusible link provides a 'slow blow'.
Some circuits might experience momentary levels of high current that
would pop a fuse but aren't harmful as long as the duration is short.
A circuit breaker might come to mind as an alternative. But these can
permit wide-spread harness damage in a case where there actually is
a short.
.
Some circuits might experience momentary levels of high current that
would pop a fuse but aren't harmful as long as the duration is short.
A circuit breaker might come to mind as an alternative. But these can
permit wide-spread harness damage in a case where there actually is
a short.
.
02-12-2006, 08:29 AM
#11
Le Mans Master
thanks for all the info-I think with that last explanation you have solved a problem for
me
I replaced a fusible link using a fuse (on my fans) ona few occasions I have blown the fuse- I know it's getting 12
volts-but just for short periods, now I can replace it with OEM fusible
links and I think that may solve my dilema.
