Fuseable link size for 8ga. wire from solenoid?

[Jonk67]

I've installed my battery/solenoid in the trunk and plan to run my wires like the MadElectrical site diagram shows:

The 8ga. wire that carries the alt. charge has 12ga. fuesable links according to the diagram. I though fuseable links were supposed to be 1 step down from the wire size, ie - 8ga. wire + 10ga. fuesable link so it heats up and burns before the wire?
Thanks,
Jon

 

[SELLERSRODSHOP]

i would go with a resettable circuit breaker or inline fuse vs. the old fuse link wire. that stuff can be a fire hazard when it cooks off, depending on the location, which in your case will be near the gas tank in the trunk.

 

[Jonk67]

I was considering those also but thought the reason a fuseable link was used is that it can heat up somewhat, then cool down if it doesn't get to max level of overload whereas the fuse or circuit breaker would trip everytime it got warm? If that's the way to go I'll have to figure out what amp to use.

I plan to pretty well seal off the gastank at the trunk floor and the solenoid will be up in the fender area by the trunk hinge mount if that helps any.
Jon

 

[AzPete]

Look for a slow blow type fuse. It can handle the initial load without blowing from a short surge.

 

[Jonk67]

What amp slow blow would be appropriately matched?
This 8ga. cable carries the charge from the alt. to the battery. The alt. is a 100A 1G large case.
Is there a way to test to see what amperage it's actually putting out at ~2K RPM? I doubt my craftsman tester is set to handle 100A readings?
Thanks, Jon

 

[buening]

8ga will hold up to 150a, so anywhere between 100a and 150a I would say. I have an ANL type fuse and fuse holder typically used for power wires for amplifier kits.

 

[Jonk67]

Ok, so you use something like this:

with a 100A fuse for the 100A alt. right? that way if the wire gets pinched and exceeds 100A it should blow the fuse? If I'm reading correctly it holds at 100A for a period of time before blowing so I don't expect it to be fed 100A very often as I don't have an electric fan, mostly just stereo stuff.

I searched for slow blow 12V fuses but didn't have any luck. I found circuit breakers but it seems a fuse would make more sense? I could carry spares which are only a few $.
Jon

 

[SELLERSRODSHOP]

if you can find a resetable slow blow circuit breaker, you wouldn't need to carry spares, only press a reset button. similar to the rollover switches ford used for the fuel pumps when everything went EFI years ago.

 

[buening]

Yeah thats like what I'm using. Mine is a 130a alternator and the wiring was 4ga. The kit I bought was for an amplifier and had the fuse sized for the wire, which I believe is 200a. If it were me I'd try to find one that is 125a or so, whether it be a circuit breaker or a fuse. Something a bit higher than the alternator output (so you don't blow them often), but something that is at or under the rated amperage for the 8ga wire you are using. You want it to protect the wire from melting/catching fire, so its not necessarily tied to the 100a alternator output.

 

[Jonk67]

Ok, so I need to figure out how much amperage my 8ga. wire will handle across ~15ft.
I found some 100 and 120A circuit breakers at Waytek which I've purchased from before and was impressed with quality. They have resettable and auto reset ones, the auto reset seems easier since it'll be tucked up in the trunk but the manual reset might be better for figuring out what's tripping it?
They're pretty reasonable at ~$22 compared to some I found that were $45:

Waytek manual reset circuit breaker

Waytek auto reset circuit breaker

I think I'm getting closer to a solution.
Jon

 

[apollard]

Waytek has great prices, but a min order of $35. But, you can order your other supplies from them, or stock up to make the $35.

 

[Jonk67]

Yes, being $22 it's more than half what's req. for a min. and i can always find electrical stuff I can use, heat shrink, wires, connectors...

Narrowed it down to:
http://order.waytekwire.com/productdeta ... 120%20AMP/
HI AMP MANUAL RESET 120 AMP
or
http://order.waytekwire.com/productdeta ... 120%20AMP/
SWITCHABLE WITH MANUAL TRIP PUSH BUTTON 120 AMP

I *think* the only difference from the paper catalog I can tell is that the switchable I can trip myself if I want which may be handy for working in the engine bay to cut power easily from the trunk. Does this sound right?

If so I guess i should get the 120A?
Thanks, Jon

 

[apollard]

The switchable would allow what you are thinking - if you wire it in the correct palce of course ;-).

120 amp should cover it IMO