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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Nathan Riddle on March 30, 2018, 10:42:35 am

Title: No fuses? No problem!
Post by: Nathan Riddle on March 30, 2018, 10:42:35 am
ECM always has an interesting article or two. This one's a doozy :)

(http://www.ecmweb.com/sites/ecmweb.com/files/styles/gal_landscape_main_2_retina/public/Define%20Qualified_1_0.jpg)

http://www.ecmweb.com/ops-maintenance/12-reasons-why-electricians-should-always-be-looking-trouble/gallery?slide=11
Title: Re: No fuses? No problem!
Post by: John Daniluk (JD) on March 30, 2018, 11:25:23 am
While running a power issue in a club, found bolts replacing the 100a fuses....

jd
Title: Re: No fuses? No problem!
Post by: John Roberts {JR} on March 30, 2018, 11:59:46 am
Back in the '70s I was repairing a custom fixture and found a length of aluminum round stock cut to length and used in place of a standard fuse. I charged an extra "stupidity tax" for that repair.

JR
Title: Re: No fuses? No problem!
Post by: Keith Broughton on March 30, 2018, 05:40:59 pm
ECM always has an interesting article or two. This one's a doozy :)

(http://www.ecmweb.com/sites/ecmweb.com/files/styles/gal_landscape_main_2_retina/public/Define%20Qualified_1_0.jpg)

http://www.ecmweb.com/ops-maintenance/12-reasons-why-electricians-should-always-be-looking-trouble/gallery?slide=11
I suspect under heavy load or a short, those copper wires would vaporize :o
Title: Re: No fuses? No problem!
Post by: Mike Sokol on March 30, 2018, 07:24:03 pm
I suspect under heavy load or a short, those copper wires would vaporize :o

Yes, we call that a fuseable link... ;)
Title: Re: No fuses? No problem!
Post by: Stephen Swaffer on March 30, 2018, 07:57:34 pm
I have seen 1/2" copper pipe flattened on each end to fit in place of a 100 amp size fuse.  Seems like more work thatn it is worth.

That said, there is a situation where a non-fused disconnect would be acceptable-if the upstream over current protective device is sized appropriately, sometimes code requires a disconnect "within sight" of a load.  If that is the case here, the only real code violation is the fact that those fuse holders are certainly not listed to be used with pieces of solid wire!
Title: Re: No fuses? No problem!
Post by: John Roberts {JR} on March 31, 2018, 09:32:05 am
I suspect under heavy load or a short, those copper wires would vaporize :o
You might be surprised by how much current that takes... About a year ago I needed to DIY a small fuse to get an amp working until replacement fuses arrived. I macgyvered a single stand of the smallest wire I could find (30ga?) tacked across the blown fuse, but decided to look up it's fuse current and that was close to 10A IIRC.  :o

 (BTW kids don't do this at home).

JR
Title: Re: No fuses? No problem!
Post by: Kevin Graf on March 31, 2018, 03:17:23 pm
Yep, fusing current for copper wire:
30AWG  ::  10.2A
12AWG ::  235A
Title: Re: No fuses? No problem!
Post by: Scott Holtzman on April 01, 2018, 06:07:30 am
Yep, fusing current for copper wire:
30AWG  ::  10.2A
12AWG ::  235A
Those values are in free air, right? 

Sent from my VS995 using Tapatalk

Title: Re: No fuses? No problem!
Post by: Kevin Graf on April 01, 2018, 09:09:31 am
Those values are in free air, right?     
Based on Preece  and Onderdonk.
https://www.powerstream.com/wire-fusing-currents.htm
Title: Re: No fuses? No problem!
Post by: Nathan Riddle on April 01, 2018, 11:47:37 am
I suspect (and I have no way to prove this), but I'd bet whoever was there "needed" it to supply power and wanted something akin to a "fuse" and used the copper wire.

The bolts sound scary...

Based on Preece  and Onderdonk.
https://www.powerstream.com/wire-fusing-currents.htm

This is schweet :) thanks!
Title: Re: No fuses? No problem!
Post by: Ivan Beaver on April 01, 2018, 02:38:21 pm
You might be surprised by how much current that takes... About a year ago I needed to DIY a small fuse to get an amp working until replacement fuses arrived. I macgyvered a single stand of the smallest wire I could find (30ga?) tacked across the blown fuse, but decided to look up it's fuse current and that was close to 10A IIRC.  :o

 (BTW kids don't do this at home).

JR
Been there, done that, more times than I will admit.  But in controlled situations, NOT for a customer to take with them.

But NOT recommended.
Title: Re: No fuses? No problem!
Post by: Mike Sokol on April 01, 2018, 02:50:01 pm
Based on Preece  and Onderdonk.
https://www.powerstream.com/wire-fusing-currents.htm

That's great, but I don't see the fusing currents for a 1/4" nutdriver.  ;D
Title: Re: No fuses? No problem!
Post by: Ron Hebbard on April 01, 2018, 03:13:52 pm
That's great, but I don't see the fusing currents for a 1/4" nutdriver.  ;D
  Hollow shaft or solid? 
Toodleoo!
Ron Hebbard.
Title: Re: No fuses? No problem!
Post by: Mike Sokol on April 01, 2018, 03:45:16 pm
Based on Preece  and Onderdonk.
https://www.powerstream.com/wire-fusing-currents.htm

Can I print this out to show the AHJ why he should ignore my solid wire jumpers in place of fuses?
Title: Re: No fuses? No problem!
Post by: John Roberts {JR} on April 01, 2018, 03:58:43 pm
HMwire has a pretty comprehensive table with multiple equations

http://www.hmwire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire.pdf (http://www.hmwire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire.pdf)

JR
Title: Re: No fuses? No problem!
Post by: Tim McCulloch on April 01, 2018, 05:11:14 pm
Can I print this out to show the AHJ why he should ignore my solid wire jumpers in place of fuses?

How about an inline "wire/fuse" holder that is protected by an appropriate (for wiring size/terminals/etc) OCPD?  You could demonstrate how much current flows through (and with an infrared camera, show the heat) a conductor about to "fuse".
Title: Re: No fuses? No problem!
Post by: Mike Sokol on April 01, 2018, 05:22:52 pm
How about an inline "wire/fuse" holder that is protected by an appropriate (for wiring size/terminals/etc) OCPD?  You could demonstrate how much current flows through (and with an infrared camera, show the heat) a conductor about to "fuse".

Back in the day we called this a "smoke test".
Title: Re: No fuses? No problem!
Post by: Tim McCulloch on April 01, 2018, 05:47:50 pm
Back in the day we called this a "smoke test".

Smoking is on the downswing, Mike. ;)

Controlled destruction for instruction!
Title: Re: No fuses? No problem!
Post by: John Roberts {JR} on April 01, 2018, 08:22:01 pm
Releasing smoke is a way to keep students awake...

JR
Title: Re: No fuses? No problem!
Post by: Dave Garoutte on April 01, 2018, 09:52:38 pm
Not to mention that the melted/exploded copper could start a fire.
Title: Re: No fuses? No problem!
Post by: Mike Sokol on April 02, 2018, 10:28:36 am
Not to mention that the melted/exploded copper could start a fire.

Yeah, and with enough amperage behind it this becomes an arc-flash. And that's very serious, indeed...
Title: Re: No fuses? No problem!
Post by: TJ (Tom) Cornish on April 03, 2018, 10:07:00 am
I suspect under heavy load or a short, those copper wires would vaporize :o
Followed by an arc flash destroying the panel and anyone unlucky enough to be near it.