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Z 16 OVP fuselink question

 
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wdaniell.longport(at)gmai
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PostPosted: Thu May 03, 2018 6:25 am    Post subject: Z 16 OVP fuselink question Reply with quote

The positive wire from the buss to master (and OVP module) to ALT relay is protected by 22AWG fuselink.

Can I use an ATC fuse instead?

I have reformed and simplified my electrical system based on AEC.  I now have a fuse buss instead of breakers etc.  I have a slot spare and to use an ATC fuse would be simpler.
Many thanks

Will


William Daniell

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user9253



Joined: 28 Mar 2008
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PostPosted: Thu May 03, 2018 10:34 am    Post subject: Re: Z 16 OVP fuselink question Reply with quote

If you have the 5 amp alternator circuit breaker, then I think it would be OK to replace the fuselink with a 30 amp fuse (or 35 if it will fit). A 22 awg fuselink can carry up to 40 amps before melting. Keep in mind that if the fuse blows, the alternator will be disconnected. It is not safe to replace a fuse while flying.

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PostPosted: Thu May 03, 2018 2:26 pm    Post subject: Z 16 OVP fuselink question Reply with quote

Joe

Thanks 
Let me refine my question...(forgive me if in being dumb)
"Is a 22awg fuselink electrically different from a 5amp ATC fuse or are they equivalent?"
Will
On Thu, May 3, 2018, 13:39 user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

If you have the 5 amp alternator circuit breaker, then I think it would be OK to replace the fuselink with a 30 amp fuse (or 35 if it will fit).  A 22 awg fuselink can carry up to 40 amps before melting.  Keep in mind that if the fuse blows, the alternator will be disconnected.  It is not safe to replace a fuse while flying.

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PostPosted: Thu May 03, 2018 5:24 pm    Post subject: Z 16 OVP fuselink question Reply with quote

At 06:51 AM 5/3/2018, you wrote:
Quote:
The positive wire from the buss to master (and OVP module) to ALT relay is protected by 22AWG fuselink.

Can I use an ATC fuse instead?

I have reformed and simplified my electrical system based on AEC. I now have a fuse buss instead of breakers etc. I have a slot spare and to use an ATC fuse would be simpler.

A piece of 22AWG wire has a hard fault
fusing characteristic on a par with a
40-50 at MaxiFuse. You could use a
MaxiFuse but it's bulkier than the
fusible link.



Bob . . .


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wdaniell.longport(at)gmai
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PostPosted: Thu May 03, 2018 5:59 pm    Post subject: Z 16 OVP fuselink question Reply with quote

Ok thanks appreciate the answer

22awg fuse link it is then.

Will

William Daniell
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On Thu, May 3, 2018, 20:28 Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

Quote:
At 06:51 AM 5/3/2018, you wrote:
Quote:
The positive wire from the buss to master (and OVP module) to ALT relay is protected by 22AWG fuselink.

Can I use an ATC fuse instead?

I have reformed and simplified my electrical system based on AEC.  I now have a fuse buss instead of breakers etc.  I have a slot spare and to use an ATC fuse would be simpler.

  A piece of 22AWG wire has a hard fault
  fusing characteristic on a par with a
  40-50 at MaxiFuse. You could use a
  MaxiFuse but it's bulkier than the
  fusible link.



  Bob . . .


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PostPosted: Fri May 04, 2018 9:02 am    Post subject: Z 16 OVP fuselink question Reply with quote

Joe and Bob,
Thanks so much...as usual a real education.   I had no idea that a 22 AWG fuselink is equivalent to a 30-40AMP fuse.   Intuitively I thought it was much less.   Much appreciated.
So if a 22AWG wire is normally "rated" to 5A which means 10degC (Ch8-Cool current rise presumably therefore needs 40A to get to melting point. 

By the same token the 16AWG fuselink at the starter contactor (from the alternator) and from the battery contactor to the buss performs in a similar way.   If this is correct the 16AWG fuselink rated at 12.5A for 10 degC current rise will melt at something like 100A.  Whereas the 12AWG wire it's protecting will melt at something like 150 .
Is this correct?   

Will

William Daniell

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+57 310 295 0744


On Thu, May 3, 2018 at 8:24 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
At 06:51 AM 5/3/2018, you wrote:
Quote:
The positive wire from the buss to master (and OVP module) to ALT relay is protected by 22AWG fuselink.

Can I use an ATC fuse instead?

I have reformed and simplified my electrical system based on AEC.  I now have a fuse buss instead of breakers etc.  I have a slot spare and to use an ATC fuse would be simpler.

  A piece of 22AWG wire has a hard fault
  fusing characteristic on a par with a
  40-50 at MaxiFuse. You could use a
  MaxiFuse but it's bulkier than the
  fusible link.



  Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1291
Location: Riley TWP Michigan

PostPosted: Fri May 04, 2018 1:08 pm    Post subject: Re: Z 16 OVP fuselink question Reply with quote

See the website below for a pdf listing the fusing (melting) current of wires. It is a lot higher than one might expect. The choice of wire size has more to do with voltage drop and insulation properties than the ampacity of the wire.
http://www.hsmwire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire.pdf


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PostPosted: Fri May 04, 2018 1:19 pm    Post subject: Z 16 OVP fuselink question Reply with quote

At 12:01 PM 5/4/2018, you wrote:
Quote:
Joe and Bob,

Thanks so much...as usual a real education. I had no idea that a 22 AWG fuselink is equivalent to a 30-40AMP fuse. Intuitively I thought it was much less. Much appreciated.

So if a 22AWG wire is normally "rated" to 5A which means 10degC (Ch8-Cool current rise presumably therefore needs 40A to get to melting point.

Exactly . . . see https://goo.gl/zye61w

Circuit protection is about keeping insulation
temperatures comfortably below maximum rated
operating vales. Wire size is all about maintaining
distribution voltage drops below acceptable levels
based on system design goals. 5% is the max-drop
rule of thumb although other values may be adopted
by program managers.

Wire sizing tends to be very conservative . . . unless
you are as weight-sensitive as a moon mission or
Voyager flight, the design rules will keep wires
pretty cool.

Quote:
By the same token the 16AWG fuselink at the starter contactor (from the alternator) and from the battery contactor to the buss performs in a similar way. If this is correct the 16AWG fuselink rated at 12.5A for 10 degC current rise will melt at something like 100A. Whereas the 12AWG wire it's protecting will melt at something like 150.

Fusible links in vehicles are expected to protect
major feeders of a distribution system against
hard faults . . . generally experienced only during
major disassembly of the vehicle. By hard fault,
were talking many times hundreds to thousands of
amps supplied by a battery . . . not the soft
fault precipitated by a failing appliance.

https://goo.gl/QEBeZs

Quote:
Is this correct?

Generally . . . When we use plain-vanilla wire
as a fusible link in the OBAM aircraft world, it's
a good idea to use the silicone/fiberglas sleeving
over it to limit the propagation of heat damage
during a fusing event. In the ground transportation
industries, fusible links are fabricated from wire
having friendlier outcomes during the fusing event.
Hypalon insulation (A Dupont product that targeted
electric locomotives in mines) is used on many
fusible link replacement assemblies available at your
local car parts stores . . . or in bulk wire on
places like eBay.

https://goo.gl/RH2eEY

The material selected for a fusible link has
little to do the loads presented by downstream
appliances. The wire in fusible link is EXPECTED
to burn . . . at many degrees above the insulation
rating. Selection of material is about reduction
of risk in the rare but catastrophic event.




Bob . . .


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