Adding fuse block.

[kencombs]

3 hours ago, JerseyHarold said:

I don't think this was mentioned, but I think I'd use a fusible link wire at the feed wires coming from the relay.  They would protect the last few inches of wiring that would otherwise be unprotected.   Mopar and others had this arrangement in the sixties and seventies.

Excellent idea but can be improved by using a Maxi-Fuse instead of the fusible link.  I've seen a few fires caused by those.  And, sometimes a failed link isn't obvious as it is hidden under insulation.  Fuse is easier to tell that it's blown.   My old F150 (1997) has TWO! 175A next to the battery.

[Eneto-55]

6 hours ago, JerseyHarold said:

I don't think this was mentioned, but I think I'd use a fusible link wire at the feed wires coming from the relay.  They would protect the last few inches of wiring that would otherwise be unprotected.   Mopar and others had this arrangement in the sixties and seventies.

The 93 Chrysler T&C had one, if I know what you're talking about.  It was a section of wire that was different - & if I recall correctly, it was labeled as a fusible link.

[Sniper]

When I rewired my 51 all the supply wires had a fusible link at the battery end of the wire.

 

My 2 speed electric fan has a fusible link for each power line to the relay.

[JerseyHarold]

4 hours ago, Eneto-55 said:

The 93 Chrysler T&C had one, if I know what you're talking about.  It was a section of wire that was different - & if I recall correctly, it was labeled as a fusible link.

That's correct.  IIRC, the fusible link wire size has to be 4 gauge numbers smaller than the wire it protects.

[D35 Torpedo]

I've old found fuseable link wire up to 10 Gauge. It is rated by gauge not amps, no idea why. 

[Sniper]

Wire is rated by gauge size not ampacity, though  there is a minimum gauge size needed to carry a certain amperage.

 

Had to replace the wire for my stove, 50A circuit.   6 gauge wire is rated at 55A max capacity and that will drop off depending on how long the run is.

 

Wire construction and composition also plays a part in it's ability to carry current.

 

Lot's of things go into rating a wire's current carrying capacity and gauge is just one factor.

 

 

[D35 Torpedo]

1 hour ago, Sniper said:

Wire is rated by gauge size not ampacity, though  there is a minimum gauge size needed to carry a certain amperage.

 

Had to replace the wire for my stove, 50A circuit.   6 gauge wire is rated at 55A max capacity and that will drop off depending on how long the run is.

 

Wire construction and composition also plays a part in it's ability to carry current.

 

Lot's of things go into rating a wire's current carrying capacity and gauge is just one factor.

 

 

I understand that. But when the wire is the fuse, I don't know why it isn't rated as such. But as long as you don't put smaller wire after the fuseable link, you'll be ok. It literally protect the feeder wire only, and shouldn't be used to protect a device. An actual fuse should be used before the device. 

[Sniper]

1 hour ago, D35 Torpedo said:

I understand that. But when the wire is the fuse, I don't know why it isn't rated as such. But as long as you don't put smaller wire after the fuseable link, you'll be ok. It literally protect the feeder wire only, and shouldn't be used to protect a device. An actual fuse should be used before the device. 

 

It would confuse the electricians, lol

 

This FAQ explains why

 

https://www.wiringdepot.com/jt-t-tech-articles/Fusible-Link-Wire-FAQs

[Bob Ritter]

I think using the fusible link as the power source is a great idea. I think most parts stores carry them, I will be adding one to my fuse box as the power source. Thanks for the idea...

 

[Eneto-55]

3 hours ago, Sniper said:

 

It would confuse the electricians, lol

 

This FAQ explains why

 

https://www.wiringdepot.com/jt-t-tech-articles/Fusible-Link-Wire-FAQs

 

Read through the article.  Other than what you all already mentioned (4 gauges smaller), they don't give any specific direction in terms of how to implement this in our setting.  (No OEM fusable link to replace).   I was wondering already before whether the sheath on these things didn't have non-flammable characteristics.  (Had wondered about covering a normal wire with non-flammable sheathing, like what is often used in industrial and household lighting sockets that are rated to accommodate high wattage bulbs, so a lot of heat.) 

 

QUOTE:

What size fusible link should be used in a new installation?
The suitability of a fusible link in a new application can be determined only by a qualified harness engineer with full knowledge of the circuit protection requirements, the installation and operating conditions, and the safety and liability aspects. We cannot make specific recommendations.

 

So which one of you all is the engineer who will figure this all out?  

 

They also mentioned use of breakers.  (I only heard of those recently, when researching what all I needed to do to wire in a 7-pin trailer connector on a vehicle that didn't have the harness already, so wondered about that as well.)

Edited August 17, 2023 by Eneto-55

[D35 Torpedo]

Man...I am an electrician lol. I didn't know about the 4 gauge less thing. Think I need to do some short circuit tests.

[Sniper]

lol, there is a reason they won't tell you, liability.

 

But seriously you already have the answer for what size to use.  The hard part is sorting out what sized wire you need, not what size fusible link.  When I converted to 12v I used an alternator rated at 78A max output.  To handle that safely I need a 6 AWG wire, which should be protected by an 10 AWG fusible link.  So what you need is a chart showing the carrying capacity of wire.

 

[D35 Torpedo]

But how is a 10g wire suppose to take 80 amps. No wonder they pop first. The only thing that makes it fuseable is the jacket.

[D35 Torpedo]

I was thinking there was something about the wire that made it melt long before the copper.

[Sniper]

Unlike a regular fuse, a fusible link doesn't pop immediately.  It can handle momentary high current spikes.  Think of it as a really slo blo fuse.

 

If you want to know more you are going to have to join SAE and read up on the white papers.

[D35 Torpedo]

So I did a test today. I took 10 gauge wire and spliced it to 10 gauge fuseable link, then I shorted it across a battery. In less than a second, the regular wire jack was erupting in smoke and fire. The fuseable link looked fine. If only all wire was jacketed in the same stuff. I'm glad this topic came up. This was something I needed to know!

[JerseyHarold]

12 minutes ago, D35 Torpedo said:

So I did a test today. I took 10 gauge wire and spliced it to 10 gauge fuseable link, then I shorted it across a battery. In less than a second, the regular wire jack was erupting in smoke and fire. The fuseable link looked fine. If only all wire was jacketed in the same stuff. I'm glad this topic came up. This was something I needed to know!

When a fusible link opens, the insulation stays intact and the wire within melts.   You need to feel along the length of the fusible link and check for any internal gaps or weak areas.

[Sniper]

Or just pull the ends of the link, the insulation will stretch if the link is gone.  Of course a meter will tell the tale too, lot's of options.

[Sam Buchanan]

My RV-6 aircraft still has the fusible link in the avionics bus feed I fabricated 25 years ago when it was wired. Fusible links were a new thing in aviation back then and there was a lot of misunderstanding about them. We used a 4"  length of wire a few gauges smaller than the primary wire (don't recall the formula, may have been four gauges smaller) and covered it with fiberglass non-flammable insulation. The rationale was the link eliminated the need to carry a fat wire to the panel to a circuit breaker with the RFI it could cause and the unprotected wire behind the panel. If a breaker pops in flight it usually isn't a good idea to try a reset so the link is a good option.

 

Just another datapoint.

[kencombs]

Overcurrent protection is a good thing.  But, as I mentioned earlier, IMO a maxi fuse (or breaker) makes much more sense than a fusible link.   More than on car fire has started due to those.   Some have been know to heat nearby insulation above the kindling point.   Fuses don't do that and are much easier to replace when and if needed.  Just like the 10/15/30s we carry in the spares kit, just add a big one and you can be back in action in minutes.  Most newer cars incorporate them.

 

My old ('97) F150 has a couple inches from the battery.  One for the fused circuits and one for unfused. 

Edited August 18, 2023 by kencombs

[Dartgame]

For anyone interested, I used a highway 22 wiring kit from american autowire. Expensive but really nice to work with and it has more circuits than I will ever need, my car is 12 volt negative ground. It has a big main breaker mounted close the battery from which everything is fed. I mounted the fuse panel inside above the foot pedals on the drivers side. The fuse panel is really easy to work with, it has screw terminals you attach the wires to as you go, and all the wires included in the kit are labelled and color coded. It has a big wiring diagram included that makes figuring out the circuits etc super easy, and step by step instruction sheets. A very complete kit.

[D35 Torpedo]

On 8/17/2023 at 6:56 PM, JerseyHarold said:

When a fusible link opens, the insulation stays intact and the wire within melts.   You need to feel along the length of the fusible link and check for any internal gaps or weak areas.

The test was to prove that the only difference between 10g fuseable link and 10g wire was the jacket. The link didn't fail. The regular jacket did. Doing this verified to me than the link needs to be made small enough that it fails before the main wires jacket.

[Bob Ritter]

My first choice was the left kick panel, but I did not want to remove the side panel cover every time I wanted to check a fuse or add a wire. And my fuse box was large and with the signal flaster it  take up a lot of room. My second choice was putting it under the seat on the drivers side, you may laugh but you have to remember that on the convertibles the wiring runs through the floor, then I would have to remove the seat every time I wanted to check a fuse. My final choice was the fire wall. I'm not trying to second guess anybody on their choices, what saying is take your time and plan it, it's a lot hard work and it something you can be proud of.