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Fuse rating question

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Posted on July 12, 2021 at 12:51:14
tweaker456
Audiophile

Posts: 7743
Location: SF Bay Area
Joined: June 20, 2020
 If the designer of a low current devise like a pre-amp calculates for a fuse of 200ma would it then be ok, safe, kosher to ignore that number and put in a 500ma fuse which is 2.5 times the current rating the one the designer of the amp thought appropriate? Thanks, Tweaker456


So let us stop talkin' falsely now, the hour's getting late --
Robert Allen Zimmerman

 

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RE: Fuse rating question, posted on July 13, 2021 at 21:21:17
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 No, you shouldn't exceed the current rating recommended by the manufacturer. Otherwise, you run the risk of doing serious damage to the component if a fault occurs in the component and the fuse doesn't blow at 200-ma to provide the required protection.

Good luck,
John Elison

 

RE: Fuse rating question, posted on July 13, 2021 at 22:41:54
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 fuses are NOT brick walls. A 1 amp fuse doens't pop at 1.01 amps instandtly.
You'll have to look at the time / current charts on the LITTLEFUSE website.

Also? As near as I can figure, you have 3 types of fuse.
Standard.....in MOST equipement regardles of current
Slo-Blow....Maybe the next most common, and will withstand higher current / time before fusing
And
FAST blo, used in some delicate electronics. Thsese pop as nearly instantly as they can engineer.

NEVER over curren the fuse. A POSSIBLE but not recommended exception? Gear requries a 2 amp slo-blo. I dont' know, but you MAY get away with a slightly larger, standard type-fuse.....But I have never heard of anyone actually DOING SO......You may want to write to an applications guy at one of the big fuse companies.
Too much is never enough

 

RE: Fuse rating question, posted on July 14, 2021 at 10:05:05
tweaker456
Audiophile

Posts: 7743
Location: SF Bay Area
Joined: June 20, 2020
 Hum, that funny. Over at Tweaker's Asylum duster is recommending a 500ma fuse in a pre-amp that came with a 200ma fuse.


So let us stop talkin' falsely now, the hour's getting late --
Robert Allen Zimmerman

 

RE: Fuse rating question, posted on July 14, 2021 at 10:41:17
Davey
 Well, if you have a legitimate failure you'd probably pop either fuse.

Sizing fuses on equipment can be more tricky than it might seem. You want to provide protection, but you also don't want nuisance openings during turn-on either. It's an iterative process, somewhat.

Cross-posting into another area so you could needle Duster is funny.

Dave.

 

RE: Fuse rating question, posted on July 14, 2021 at 10:43:03
tweaker456
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Posts: 7743
Location: SF Bay Area
Joined: June 20, 2020
 Probably maybe but not definitely.


So let us stop talkin' falsely now, the hour's getting late --
Robert Allen Zimmerman

 

Good point!, posted on July 14, 2021 at 12:44:12
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Since you're the owner, you can actually use any size fuse you want that's equal to or greater than 200-mA. So long as no circuit faults occur, you'll be just fine. But, if anything should happen to go wrong, there's greater risk of serious damage when using a fuse larger than 200-mA.

Best regards,
John Elison

 

RE: Fuse rating question, posted on July 14, 2021 at 14:07:14
tweaker456
Audiophile

Posts: 7743
Location: SF Bay Area
Joined: June 20, 2020
 If I recommended a fuse 2.5 times what the designer calculated for I would have been nail to a cross. I can tell you that!




So let us stop talkin' falsely now, the hour's getting late --
Robert Allen Zimmerman

 

RE: Fuse rating question, posted on July 14, 2021 at 14:46:37
Davey
 No, but you probably would have been questioned about it. :)
I'm not sure why you're twisted up about this. I quit taking Duster seriously years ago.

Dave.

 

RE: Fuse rating question, posted on July 14, 2021 at 17:32:04
tweaker456
Audiophile

Posts: 7743
Location: SF Bay Area
Joined: June 20, 2020
 +1


So let us stop talkin' falsely now, the hour's getting late --
Robert Allen Zimmerman

 

RE: Fuse rating question, posted on July 15, 2021 at 07:25:40
sony6060
Audiophile

Posts: 1465
Location: USA
Joined: August 8, 2014
 Fast Blow fuse, use 2x current draw. Slow Blow fuse, use 1.25 times the current draw. Fuses can operate up to 1.5x the fuse current rating for up to 20 minutes.
Personally, I use Slow blow at as close to current draw as possible with capacitor input power supplies. Choke input power supplies not having a high input charging surge, I use Fast Blow at as close to current rating as possible. Never had a fuse fail.

 

Try this view, posted on July 20, 2021 at 08:47:56
mlsstl
Audiophile

Posts: 1079
Location: Midwest
Joined: September 1, 2015
 Most circuits have multiple components. Consider that, with a 200 mA fuse, for example, you may lose one component before the fuse pops, but still protect other components in the circuit. With a 500 mA fuse, you may still be protected from starting a fire, but end up losing multiple components in the circuit before it pops.

 

Since they're cheap, posted on July 27, 2021 at 14:33:49
E-Stat
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Posts: 37666
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 just get a small supply of the correct value.

 

RE: Fuse rating question, posted on August 30, 2021 at 13:46:17
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 If circuit stayed perfect forever, you would NOT need a fuse.

I'd personally try to get the fuse recommended by the designer / builder.....but that's just me.


Too much is never enough

 

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