blew a fuse

[ManWonder]

so i added a 12v power outlet for my wife to plug her laptop into. the thing pulls 8 amps. all i did was tap into the wires that go to the propane leak monitor. little did i know the fuse at the fuse box was a 1 amp fuse. the wires i tapped into sure looked beefy enough to handle the load. so i reckon i will look for a better place to tap in. Or would it be safe to upgrade the fuse to a 10 amp?

[Bruceper]

No.

The fuse is 1 amp because that is the current threshold for your propane leak monitor. By changing that fuse to an 8 amp fuse (which probably doesn't exist, likely 10 amp) you would be permitting 800% of the maximum current into that circuit before the fuse would blow.

If there was a problem in this circuit, that would likely mean a fire before the fuse did it's job to prevent such a fire.

Find a new circuit, or make a new one if you are able to.

[BBQ]

Originally Posted by ManWonder

so i added a 12v power outlet for my wife to plug her laptop into. the thing pulls 8 amps. all i did was tap into the wires that go to the propane leak monitor. little did i know the fuse at the fuse box was a 1 amp fuse. the wires i tapped into sure looked beefy enough to handle the load. so i reckon i will look for a better place to tap in. Or would it be safe to upgrade the fuse to a 10 amp?

I would pull a wire directly from the fuse box.

Tapping a line will only create problems further down the road.

[Johnny R]

I get a little nervous when someone even considers replacing an electrical fuse with one allowing 10 times more current to pass through than intended, and wonders if there might be a problem.

[cruising7388]

Originally Posted by ManWonder

so i added a 12v power outlet for my wife to plug her laptop into. the thing pulls 8 amps. all i did was tap into the wires that go to the propane leak monitor. little did i know the fuse at the fuse box was a 1 amp fuse. the wires i tapped into sure looked beefy enough to handle the load. so i reckon i will look for a better place to tap in. Or would it be safe to upgrade the fuse to a 10 amp?

Her laptop is pulling 100 watts? How long does this laptop function on its own battery?

[ManWonder]

Originally Posted by Johnny R

I get a little nervous when someone even considers replacing an electrical fuse with one allowing 10 times more current to pass through than intended, and wonders if there might be a problem.

yeah i get that and generally speaking i am no dummy but... it just surprised me that with the thickness of the wiring i tapped into they fused it at 1 AMP - so I got to thinking this might be a dedicated fuse for the detector and no harm might be done if i added another load and changed out the fuse accordingly - i could have put an inline 1 amp fuse ahead of the detector to protect it from harm - anyways, i knew enough to ask the question -

i will likely try running a separate wire if i can find a place in the fuse box for another fuse -- thanks all

[avanti]

Originally Posted by ManWonder

it just surprised me that with the thickness of the wiring i tapped into they fused it at 1 AMP - so I got to thinking this might be a dedicated fuse for the detector and no harm might be done if i added another load and changed out the fuse accordingly - i could have put an inline 1 amp fuse ahead of the detector to protect it from harm

Although I agree that it is best to just run another wire, the reasoning you state above is not wrong, and some of the opinions offered on this thread are a bit overstated.

Fuses are not intended to protect devices, they protect WIRING. If in fact the wire in question has an ampacity rating of 10 amps, then it is perfectly safe to protect it with a 10 amp fuse. It really makes no difference that the propane monitor uses much less current--it will only take what it needs. BUT, you need to be absolutely sure that the ENTIRE CIRCUIT is rated for 10 amps. The design engineer may well have taken advantage of the protection of the 1 amp fuse in order to safely cut a corner somewhere. It is generally easier to run a new wire than it is to trace the circuit in order to ensure this.

It is not unusual to find a fuse that was spec'd to the load rather than the circuit. This provides an extra margin of protection and is generally considered best practice. If this is the ONLY reason why the fuse is small, it is perfectly OK to upsize it. But it is often no easy task to determine that with confidence.

[ManWonder]

Originally Posted by avanti

It is not unusual to find a fuse that was spec'd to the load rather than the circuit. This provides an extra margin of protection and is generally considered best practice. If this is the ONLY reason why the fuse is small, it is perfectly OK to upsize it. But it is often no easy task to determine that with confidence.

Also along this line I was wondering might there be a tool the pros use that can determine easily and quickly the rating of a given circuit.

[InterBlog]

What Avanti said was nicely stated, very coherent.

The other thing to keep in mind is to be careful about what laptops claim vs. what they do, because they are not all created equally. Hopefully what they claim will, if anything, be overstated relative to their actual demands, but it's iffy to rely on that right out of the box.

I have a large "mobile workstation" and my husband and I recently completed a lithium upgrade that was, in part, bracketed by the fact that the workstation might (per spec) draw up to 230 watts. In practice, it seems to want less than that, even when charging, but I haven't put it through all its paces yet.

[BBQ]

Originally Posted by ManWonder

yeah i get that and generally speaking i am no dummy but... it just surprised me that with the thickness of the wiring i tapped into they fused it at 1 AMP - so I got to thinking this might be a dedicated fuse for the detector and no harm might be done if i added another load and changed out the fuse accordingly - i could have put an inline 1 amp fuse ahead of the detector to protect it from harm - anyways, i knew enough to ask the question -

i will likely try running a separate wire if i can find a place in the fuse box for another fuse -- thanks all

No question is a dumb question.

We should all be glad that you asked.
The answers are not only for you, but for all the gawkers who read the forum anonymously.


ps. I would prefer not to use an inline fuse; because when it blows 5 yrs from now, you (or the new owner) will have a hard time tracing the problem.