Today's Message Index:
----------------------
1. 03:33 AM - A couple of questions about Fuses (Carlos Trigo)
2. 06:17 AM - Re: A couple of questions about Fuses (Art Zemon)
3. 06:29 AM - Re: A couple of questions about Fuses (Charlie England)
4. 06:37 AM - Re: A couple of questions about Fuses (user9253)
5. 08:09 AM - Re: Re: A couple of questions about Fuses (C&K)
6. 07:06 PM - Securing Split PVC Conduit (Art Zemon)
Message 1
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Subject: | A couple of questions about Fuses |
Good morning 'letric Bob and all 'letric experts.
I hope you had a Merry Christmas!
In my fused power busses I decided to use LED blade fuses, those whose LED
gets illuminated when the fuse trips.
It happens that I have a couple of circuits which require a 1A fuse, but
there are no 1A LED blade fuses. Therefore, in these circuits, either I use
a normal (non-illuminated) 1A fuse, or I go for a 2A illuminated fuse.
What happens if I decide for the latter? Do I get less protection? Is that
particular device more prone to be fried?
Now, for the second question, in a broader perspective: I have heard dozens
of times that a fuse (or other protection device) is there to protect the
wire and not the device at its end.
However, the size (in A) of the fuse is determined by the device in use (you
read in the installation manuals that "to protect this device, you should
use a 3A fuse or circuit breaker").
I know that this depends on the power (W) that is used by the device when
working, and that both the wire and the fuse must be sized accordingly. I
also know that if we use a thinner wire, it will get very hot and eventually
melt.
But what about using an higher A or a lesser A fuse? What are the physics
involved?
Thanks
Carlos
Message 2
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Subject: | Re: A couple of questions about Fuses |
Hi Carlos,
Take a look at chapter 10, circuit protection, in *The AeroElectric
Connection*. And here are a few articles:
http://www.aeroelectric.com/articles.html#Circuit Protection
In building my plane, I am following the advice to size the fuse for the
wire, except in a couple of cases where I only need a couple of amps and
did not feel like installing tiny wire. In those cases, I went ahead and
used an undersized fuse, even though the wire is capable of carrying more
current.
Cheers,
-- Art Z.
On Mon, Dec 26, 2016 at 5:31 AM, Carlos Trigo <trigo@mail.telepac.pt> wrote
:
> Good morning =98letric Bob and all =98letric experts.
>
> I hope you had a Merry Christmas!
>
>
> In my fused power busses I decided to use LED blade fuses, those whose LE
D
> gets illuminated when the fuse trips.
>
> It happens that I have a couple of circuits which require a 1A fuse, but
> there are no 1A LED blade fuses. Therefore, in these circuits, either I u
se
> a normal (non-illuminated) 1A fuse, or I go for a 2A illuminated fuse.
>
> What happens if I decide for the latter? Do I get less protection? Is tha
t
> particular device more prone to be fried?
>
>
> Now, for the second question, in a broader perspective: I have heard
> dozens of times that a fuse (or other protection device) is there to
> protect the wire and not the device at its end.
>
> However, the size (in A) of the fuse is determined by the device in use
> (you read in the installation manuals that =9Cto protect this devic
e, you
> should use a 3A fuse or circuit breaker=9D).
>
> I know that this depends on the power (W) that is used by the device when
> working, and that both the wire and the fuse must be sized accordingly. I
> also know that if we use a thinner wire, it will get very hot and
> eventually melt.
>
> But what about using an higher A or a lesser A fuse? What are the physics
> involved?
>
>
> Thanks
>
> Carlos
>
--
https://CheerfulCurmudgeon.com/
*"If I am not for myself, who is for me? And if I am only for myself, what
am I? And if not now, when?" Hillel*
Message 3
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Subject: | Re: A couple of questions about Fuses |
Charlie
On Dec 26, 2016, 6:40 AM, at 6:40 AM, Carlos Trigo <trigo@mail.telepac.pt> wrote:
>Good morning 'letric Bob and all 'letric experts.
>
>I hope you had a Merry Christmas!
>
>
>
>In my fused power busses I decided to use LED blade fuses, those whose
>LED
>gets illuminated when the fuse trips.
>
>It happens that I have a couple of circuits which require a 1A fuse,
>but
>there are no 1A LED blade fuses. Therefore, in these circuits, either I
>use
>a normal (non-illuminated) 1A fuse, or I go for a 2A illuminated fuse.
>
>What happens if I decide for the latter? Do I get less protection? Is
>that
>particular device more prone to be fried?
>
>
>
>Now, for the second question, in a broader perspective: I have heard
>dozens
>of times that a fuse (or other protection device) is there to protect
>the
>wire and not the device at its end.
>
>However, the size (in A) of the fuse is determined by the device in use
>(you
>read in the installation manuals that "to protect this device, you
>should
>use a 3A fuse or circuit breaker").
>
>I know that this depends on the power (W) that is used by the device
>when
>working, and that both the wire and the fuse must be sized accordingly.
>I
>also know that if we use a thinner wire, it will get very hot and
>eventually
>melt.
>
>But what about using an higher A or a lesser A fuse? What are the
>physics
>involved?
>
>
>
>Thanks
>
>Carlos
Message 4
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Subject: | Re: A couple of questions about Fuses |
Fuses that glow when blown depend on the load to complete the circuit. If the
load circuit happens to open up as a result of the malfunction, the fuse will
not glow. While the above scenario is possible, it is not likely. If some electrical
device does not work, check the glow-type fuse with a meter to be sure
that it is not blown.
Yes, the larger the fuse, the less protection there is. By protection, I am
talking about protection against smoke in the cockpit. As far as protection for
the electrical device, it doesn't matter if the fuse is 1 amp or 2 amps or
5 amps. If the device shorts out, it will be fried regardless of the fuse size.
A lager fuse size will not make any electrical device more prone to fail.
Many devices have internal fuses to protect against internal short circuits.
22 AWG wire can be protected by a 3 amp fuse. But if a device only requires one
half amp, then a 1 amp fuse will offer more protection against smoke if the
device ever shorts out.
Bottom line is, you can use either a 1 amp or 2 amp fuse. A 1 amp will give
more peace of mind. A 2 amp will work too.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=464402#464402
Message 5
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Subject: | Re: A couple of questions about Fuses |
I would add that I have seen cases where the recommended small fuse
popped after many years. Replacing the fuse with a handy slightly larger
fuse also popped but this time it was accompanied by smoke from the
transponder. Neither fuse put the wire at any risk and likely the smoke
would have stopped by itself but I prefer to follow the manufacturers
fuse recommendation. OTOH I don't worry about going up to the
appropriate larger wire protection fuse in cases where it is convenient
to put multiple items on the same fuse.
Of larger concern to me are some of the very small gage cords that get
plugged into 15 amp circuits in houses.
Ken
On 26/12/2016 9:35 AM, user9253 wrote:
>
> Fuses that glow when blown depend on the load to complete the circuit. If the
load circuit happens to open up as a result of the malfunction, the fuse will
not glow. While the above scenario is possible, it is not likely. If some
electrical device does not work, check the glow-type fuse with a meter to be sure
that it is not blown.
> Yes, the larger the fuse, the less protection there is. By protection, I
am talking about protection against smoke in the cockpit. As far as protection
for the electrical device, it doesn't matter if the fuse is 1 amp or 2 amps
or 5 amps. If the device shorts out, it will be fried regardless of the fuse
size. A lager fuse size will not make any electrical device more prone to fail.
Many devices have internal fuses to protect against internal short circuits.
> 22 AWG wire can be protected by a 3 amp fuse. But if a device only requires
one half amp, then a 1 amp fuse will offer more protection against smoke if
the device ever shorts out.
> Bottom line is, you can use either a 1 amp or 2 amp fuse. A 1 amp will give
more peace of mind. A 2 amp will work too.
>
> --------
> Joe Gores
>
>
Message 6
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Subject: | Securing Split PVC Conduit |
Folks,
I am using some split PVC conduit
<http://www.hall-fast.com/consumables/electrical/cable-accessories/conduit-and-warning-tapes/pvc-split-conduit/>
in my plane and two of the runs are pretty close to vertical, about 4 feet
long. Sitting in my garage, with the wires not yet secured at the bottom,
the conduit keeps trying to slide downward in the 2 inch square channels
through which it runs. I think that I ought to secure it somehow and wonder
if you have any ideas that will keep it in place.
Maybe I can wrap a thin cable tie around it and get it to slip into a
groove?
Or maybe wrap it with silicone self-sealing tape and the put an AN742 clamp
around it?
Thanks,
-- Art Z.
--
https://CheerfulCurmudgeon.com/
*"If I am not for myself, who is for me? And if I am only for myself, what
am I? And if not now, when?" Hillel*
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