Fuse question....

[Bryanmc57]

If an Echomap Ultra 106 draws ~2.8 amps and a GLS10 draws ~1 amp, why do they both come with an 8 amp fuse in the power cable?

[BobKlindworth]

The fuse is designed to protect the internal electronics of the unit. The engineers that designed the units have determined that it can safely draw up to 8 amps, even though a typical draw is much less than that. Under-fusing a device can cause nuisance fuse failures that clients find annoying, so the practice is to fuse them for safety rather than for assumed typical draw.

[Titansfan2104]

If an Echomap Ultra 106 draws ~2.8 amps and a GLS10 draws ~1 amp, why do they both come with an 8 amp fuse in the power cable?

The fuse is to protect the wiring. You fuse according the the size wire , regardless what's on the other end. That's why you fuse as close to the power source as possible.

[majatk]

Also amps vary ,Garmin specs say GLS10 power usage is

21 W typical, 58 W max
Since watts = amps x volts , amps will depend on if your using a lead acid @ 12v or a lifepo4 @ 13.2 v ,or a NMC @ 14.8 v
watts divided by volts = amps

[bassfisher444]

Fuses protect the wiring not the equipment.

[BobKlindworth]

Ok, my mistake then. Does the equipment just shunt excessive current to ground then?

[billnorman1]

The equipment or load uses as much current as it is designed to. It does not draw more. The current on the fuse says what current it is supposed to carry before opening. It does not change the current used, the equipment or load does.

[BobKlindworth]

Understood. So why are there ever in-line fuses? If the unit will never draw more than its max current rating, the wire that supplies it would never exceed its safe operating current either. 14awg has a max safe operating current of 15 amps. Fusing for 8A in-line when the max current drawn by the load is 5A seems pointless.

[Titansfan2104]

Understood. So why are there ever in-line fuses? If the unit will never draw more than its max current rating, the wire that supplies it would never exceed its safe operating current either. 14awg has a max safe operating current of 15 amps. Fusing for 8A in-line when the max current drawn by the load is 5A seems pointless.

Because you have direct short to ground that causes resistance which increases amps which causes wires to melt which leads to fires. :) Not to say it wont protect the electronics but the main reason is to prevent wire failures and fires!!

[Bryanmc57]

Because you have direct short to ground that causes resistance which increases amps which causes wires to melt which leads to fires. :) Not to say it wont protect the electronics but the main reason is to prevent wire failures and fires!!

I understand the purpose of the fuse, My question was why fuse the line for 2 - 3 times the max load?

[Lowerider58]

I understand the purpose of the fuse, My question was why fuse the line for 2 - 3 times the max load?

If a component in the unit fails and shorts out current would increase. The fuse would blow to stop the current.

[BobKlindworth]

Because you have direct short to ground that causes resistance which increases amps which causes wires to melt which leads to fires. :) Not to say it wont protect the electronics but the main reason is to prevent wire failures and fires!!

So fusing is done in case of a wiring failure that shorts the power cord wire to ground. Ok. A sort of unlikely situation if the wiring is done by someone competent, but I suppose the Dunning-Kruger effect is real.

[billnorman1]

So fusing is done in case of a wiring failure that shorts the power cord wire to ground. Ok. A sort of unlikely situation if the wiring is done by someone competent, but I suppose the Dunning-Kruger effect is real.

That or the unit has an internal failure which causes it to draw excessive current such as a short. Hypothetically if a unit such as a motor, or electronic unit fails in such a way, it could burn up the wire with disasterous results. Ergo the fuse or circuit breaker device opens, effectively eliminating the path for electrical energy. Thus, although inconvenienced by the unavailability to use said feature, the wiring is saved for service with a functional replacement or repaired item after fuse replacement.

[majatk]

I understand the purpose of the fuse, My question was why fuse the line for 2 - 3 times the max load?

Not really 2-3 times
If on a 12v lead acid or agm and the battery is run down to 10 volts (garmin says 10-32 v) the amps would be 5.8 at max watts of 58
Unlikely to happen