Adding An Accessory Outlet

[MikeyT]

Originally Posted by toothy

I love this place.


On that sunday morning when I got the bug to do a little project I remembered I wanted to get power to the GPS on the dirtbike. So off to the Schuck's auto parts store. (why do auto parts stores have the chintzy-est products- everything there is low grade merch.) Anyway, I buy a rubber coated cig lighter outlet with 12ga pigtails and a mini fuse holder that's also rubber coated with a rubber cap and 12ga pigtails. The blister package says "30 AMP". So I get set to wire it up and think the better way is to ask the collective wisdom on here.

Needlesss to say the fuse holder had no fuses in it, so back to the store I went I enede up with a multi-pack.

so the answer is 12 gague wire.

12 ga. wire, 15 amp max. IMO

[xtphreak]

Originally Posted by greywolf

... and the equipment fuse protects the equipment. A GPS will typically have a vehicle adapter for power. The adapter will most likely drop the 12V to 5V and have a built in fuse of no more than 3A.

how?

if the GPS pulls more than 3A what then?

ok the fuse opens

now what?

put another fuse in and it pops.

what now?


the GPS is toast is what.

and the fuse did NOT protect it.

if a device draws more than it's designed to it's broke.

so how did the fuse protect it?

from letting excesive magic white smoke out?

right

out of the device and / or the wire feeding the device

it is NOT there to protect the device

[xtphreak]

Originally Posted by RatBob

12 ga. wire, 15 amp max. IMO

NFPA79



33CFR183




take yer pick

[greywolf]

http://www.powerstream.com/Wire_Size.htm indicates 14ga chassis wire can handle 32 amps. If the GPS pulls more than 3A, something went wrong and some part inside is fried or a wire is shorted. If shorted, there's a chance the short can be separated and the GPS function again. If fried, the fuse blows so more parts don't also die. Chances are it can be repaired. If a 10A line fuse was the only fuse in the circuit, the entire GPS is more likely to be toast. It's also possible for a regulator failure to feed too high a voltage into the GPS and blow the fuse before the GPS is damaged. Many pieces of equipment have their own fuse or circuit breaker. There is a reason for it.

[xtphreak]

Originally Posted by greywolf

http://www.powerstream.com/Wire_Size.htm indicates 14ga chassis wire can handle 32 amps. If the GPS pulls more than 3A, something went wrong and some part inside is fried or a wire is shorted. If shorted, there's a chance the short can be separated and the GPS function again. If fried, the fuse blows so more parts don't also die. Chances are it can be repaired. If a 10A line fuse was the only fuse in the circuit, the entire GPS is more likely to be toast. It's also possible for a regulator failure to feed too high a voltage into the GPS and blow the fuse before the GPS is damaged. Many pieces of equipment have their own fuse or circuit breaker. There is a reason for it.

Originally Posted by greywolf

http://www.powerstream.com/Wire_Size.htm indicates 14ga chassis wire can handle 32 amps...

SO look at 30A @ 12 vdc.
the line loss calculator shows 0.934 volts of line loss on a 14AWG wire 6 feet long.
call it a volt.
that's 30 watts of heat that the wire has to disperse.

what's the ambient temp where the wire is, say under the tank over the head?
what's the insulation's temp rating?

"...In careful engineering the insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account."
(http://www.powerstream.com/Wire_Size.htm)

use whatever wire you want, we've been here before.
what they're talking about is a bare conductor in free air, not a wire with insulation in a hot environment.

you quote a small company, I'll continue to quote NFPA and/or applicable Codes.

Originally Posted by greywolf

...If the GPS pulls more than 3A, something went wrong and some part inside is fried or shorted...

yep, it's broke

Originally Posted by greywolf

...If shorted, there's a chance the short can be repaired and the GPS function again. If fried, the fuse blows so more parts don't also die. Chances are it can be repaired. If a 10A line fuse was the only fuse in the circuit, the entire GPS is more likely to be toast ...

wishful thinking
do you think the manufacturers calculate the current if this or that shorts, or this fries?

Originally Posted by greywolf

...It's also possible for a regulator failure to feed too high a voltage into the GPS and blow the fuse before the GPS is damaged. Many pieces of equipment have their own fuse or circuit breaker. There is a reason for it.

it ain't voltage that's gonna open that fuse, it's current.

you can look at fuses all day and you'll see 120v rated fuses in 12 vdc applications and there's nothing wrong with that

fuses are time rated devices because they work on heat

you cannot expect a fuse to open fast enough to stop a voltage transient

why is the fuse located at the source end of the supplied cable rather than at the device itself?

to fuse the wire