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1 Amp Fuses

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mpetersen(at)repsol.com.a
Guest

Posted: Tue Sep 11, 2007 7:56 pm Post subject: 1 Amp Fuses

G’day Bob and List Members,  

   

I have come across a number of equipment manufacturers that specify a 1 amp fuse for their equipment (eg Ray Allen trim systems) and I am using a mini blade type fuse block in my aircraft. The smallest fuse I can find is 2 amps, which leads me towards the following alternatives;  

     Stick to the philosophy of      selecting the fuse to suit the wire (22awg in this case) and ignoring the      manufacturer’s requirement.  
Use the 2 amp blade fuse, being      the closest available.  
Incorporating some other type of 1      amp circuit protection, for example a small circuit board being supplied      via the main bus/fuse block that provides several 1 amp circuits protected      by a PTC type fuse.    

   

My question is, is there a recognized ‘correct’ way of dealing with this issue, or what is the preferred solution?  

   

Bob, I have read your critique of Greg Richter’s “Aircraft Wiring for Smart People”, in which you very briefly mention that PTC fuses are not suitable for use in aircraft. Could you please elaborate on your research and findings? By the way, I am half way through reading your book and would like to thank you for the effort you put into helping people like me understand these issues! Keep up the good work!  

   

Thanks,  

   

Michael  

   

      [quote][b]

jindoguy(at)GMAIL.COM
Guest

Posted: Wed Sep 12, 2007 5:20 am Post subject: 1 Amp Fuses

Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea. 



Rick



On 9/11/07, Michael Petersen <mpetersen(at)repsol.com.au  (mpetersen(at)repsol.com.au)> wrote:[quote]                     

G'day Bob and List Members,  

   

I have come across a number of equipment manufacturers that specify a 1 amp fuse for their equipment (eg Ray Allen trim systems) and I am using a mini blade type fuse block in my aircraft. The smallest fuse I can find is 2 amps, which leads me towards the following alternatives;  

     Stick to the philosophy of      selecting the fuse to suit the wire (22awg in this case) and ignoring the      manufacturer's requirement.  
Use the 2 amp blade fuse, being      the closest available.  
Incorporating some other type of 1      amp circuit protection, for example a small circuit board being supplied      via the main bus/fuse block that provides several 1 amp circuits protected      by a PTC type fuse.     

   

My question is, is there a recognized 'correct' way of dealing with this issue, or what is the preferred solution?  

   

Bob, I have read your critique of Greg Richter's "Aircraft Wiring for Smart People", in which you very briefly mention that PTC  fuses are not suitable for use in aircraft. Could you please elaborate on your research and findings? By the way, I am half way through reading your book and would like to thank you for the effort you put into helping people like me understand these issues! Keep up the good work!  

   

Thanks,  

   

Michael  

   

      [quote][b]  http://www.matronics.com/Navigator?AeroElectric-List http://forums.matronics.com 

when you live at the airport.  [quote][b]

aurbo(at)ak.net
Guest

Posted: Wed Sep 12, 2007 6:35 am Post subject: 1 Amp Fuses

Michael,

  

  

Tech-Tips 

PTC's vs. Fuses                   

PTC's act as a type of circuit breaker; the resistance increases as the        PTC threshold temperature is exceeded due to the load current passing        through the device. This causes high resistance which opens the circuit        protecting the device in the event of an over current condition. Unlike        fuses, ambient temperature plays a role in how long it will be before a        PTC reacts to over current. For this reason, careful consideration should        be given to when PTC's are used for equipment protection.       

A PTC is appropriate for battery protection as most battery shorts are        heavy shorts quickly tripping the PTC. The PTC is best for devices that        can tolerate high current for a substantial amount of time, such as        batteries.        

Because PTC's are slow acting and have a less accurate trip threshold,        the PTC may not protect the cameras as reliably as a fast acting fuse.        Because PTC's need to cool down to reset and will not do so if the over        current condition is not corrected, a service call will probably be needed        to address the failure.        

A one amp PTC may never blow at 2 amps and may require more than 30        seconds to blow at 5 amps. A one-amp fuse should blow at 1.25 amps in        about 1 second, regardless of conditions. It is much more economical for        the dealer/customer to replace a simple fuse rather than an expensive        piece of electronics.        

This came off of the:  www.pthree.com/techtips.aspx       

Doesn't seem like the PTC is a good        idea.       

Mike       

 

 [quote]   ---

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Wed Sep 12, 2007 8:56 am Post subject: 1 Amp Fuses

In a message dated 09/11/2007 10:58:26 PM Central Daylight Time, mpetersen(at)repsol.com.au writes:

  	  Quote: 	
		  Stick to the philosophy of selecting the fuse to suit the wire (22awg in this case) 	


 Yes.  2-amp fuse would be fine, IMHO.

  

 Mark do not archive



See whattarget="_blank">Make AOL Your Homepage.

  [quote][b]

_________________
From The PossumWorks...

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 12, 2007 1:45 pm Post subject: 1 Amp Fuses

At 08:18 AM 9/12/2007 -0500, you wrote:



 	  Quote: 	
		  Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.



Rick


	


   B&C stocks them too.



   If you do a google search on "ATC-1" and "fuse" you'll

   find lots of other folks have them too.



   Bob . . .

dgolden(at)golden-consult
Guest

Posted: Wed Sep 12, 2007 2:43 pm Post subject: 1 Amp Fuses

Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)cox.net>

 At 08:18 AM 9/12/2007 -0500, you wrote:

> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.

>

> Rick

   B&C stocks them too.

   If you do a google search on "ATC-1" and "fuse" you'll

   find lots of other folks have them too.

I thought the original post stated that the fuse box was for miniature

(i.e. ATM) fuses. I've had problems finding anything less that 2 amp also.

Dennis

-- 

Dennis Golden

Golden Consulting Services, Inc.

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 12, 2007 6:13 pm Post subject: 1 Amp Fuses

At 05:42 PM 9/12/2007 -0500, you wrote:



 	  Quote: 	
		  

<dgolden(at)golden-consulting.com>



Robert L. Nuckolls, III wrote:

 > 

 > <nuckolls.bob(at)cox.net>

 >

 > At 08:18 AM 9/12/2007 -0500, you wrote:

 >

 >> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.

 >>

 >> Rick

 >

 >   B&C stocks them too.

 >

 >   If you do a google search on "ATC-1" and "fuse" you'll

 >   find lots of other folks have them too.



I thought the original post stated that the fuse box was for miniature

(i.e. ATM) fuses. I've had problems finding anything less that 2 amp also.


	


   Opps. My bad. Yes, the ATM spec sheet



http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATM_Specs.pdf



   says 2A is as small as they go in that form-factor unlike

   the ATC sheet



http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATC_Specs.pdf



   which takes us down to 1A. I didn't go back to the original

   post. Sooooo . . .



G'day Bob and List Members,



I have come across a number of equipment manufacturers that specify

a 1 amp fuse for their equipment (eg Ray Allen trim systems) and

I am using a mini blade type fuse block in my aircraft. The smallest

fuse I can find is 2 amps, which leads me towards the following

alternatives;



Stick to the philosophy of selecting the fuse to suit the wire

(22awg in this case) and ignoring the manufacturer's requirement.

Use the 2 amp blade fuse, being the closest available.



    This would probably be just fine. I've always had a bit

    of heartburn about manufacturer's "suggestions" that

    their device would benefit from some degree of protection

    by installation . . . which the installer is expected to

    supply. Having said that - I HAVE designed systems using

    appliances with very light draw (under 1A) where

    their 22AWG feeders were protected with small fuses. This

    is pretty easy when the system is wired with the ATC

    fuseblocks. Harder as you've noted in alternative

    fuseblock products.



Incorporating some other type of 1 amp circuit protection, for

example a small circuit board being supplied via the main bus/fuse

block that provides several 1 amp circuits protected by a PTC type fuse.



    The 2A fuse will be fine. As you've already noted, the

    PTC is not easily integrated into a system. The small,

    solid wire lead components are designed to be integrated

    inside a device and demand some appliance design,

    fabrication and installation (i.e., super-whippy power

    distribution assembly boards).



My question is, is there a recognized 'correct' way of dealing with

this issue, or what is the preferred solution? Bob, I have read your

critique of Greg Richter's "Aircraft Wiring for Smart People",

in which you very briefly mention that PTC fuses are not suitable

for use in aircraft. Could you please elaborate on your research

and findings?

    I'm not sure I've ever used the words "not suitable" but

    there have been many a discussion between myself an individuals

    who were touting products that incorporated the PTC (aka polyswitch,

    and polyfuse). A few documents in addition to the Richter discussion

    include:



http://www.aeroelectric.com/FAQ/AeroElectric-List/AeroElectric-List_FAQ.pdf



http://www.aeroelectric.com/articles/expbusthd.html



http://www.aeroelectric.com/articles/expbusad.html



    The polyswitch was first presented to me about 1982 by my

    very good friend Jim West who at the time was a Raychem

    rep with Thunderbird aviation. I had the electrical/

    avionics group on the GP-180 and Jim thought perhaps

    this nifty device would find useful applications in

    the airframe arena.



    First, let me be quite clear that incorporation of

    the polyswitch NEVER raised questions with respect to

    safety. It was never pushed aside for failure to do the

    tasks that fuses, breakers and other FIRE PROTECTION devices

    have accomplished for over a century.



    The questions about PTC circuit protection have to

    do with (1) $value$ of the trade-off and (2) integration

    into the overall system design philosophy.



    PTC's are loose components intended to solder to an

    etched circuit board. This means that unlike a collection

    of fuses or breakers (which are easily integrated into

    a wide variety of designs as individual components)

    an array of PTC devices becomes an appliance - an

    assembly that in the TC aircraft world requires

    qualification. Those qualification test would most

    certainly include vibration and operation over temperature

    extremes.



    In the OBAM aircraft world, the appliance grows features

    like pre-assembled switch panels, avionics bus noise

    filters and power management, voltage regulators, etc.

    The more features that are added, the less adaptable

    becomes the appliance. What you see is what you get . . .

    take it or leave it. And whether or not you want or

    need all those features, the cost is not insignificant.



    In the TC world, I participated in three explorations

    with others. Once at Learjet and twice at Beech to

    see if the PTC offered any features attractive to

    our program managers and customers . . . and the FAA.

    Had more than one FAA type objecting to the "self re-setting

    feature of PTCs . . . when a hazardous fault operates

    the circuit protection, present conventions call for

    the system to open and stay open pending repairs.



    Many have read my writings about the various products

    that feature PTCs and have mis-interpreted the down-side

    observations to be an attack on PTCs as protective

    devices. Again, they do the job they were designed to

    do in the manner described in their sales literature.

    The BIG picture speaks to poor $value$ and loss of some

    operational and architecture control when appliances

    (perhaps combined with other components) are used to

    replace loose breakers or inexpensive fuseblocks.

By the way, I am half way through reading your book and would like

to thank you for the effort you put into helping people like me

understand these issues! Keep up the good work!



    You HAVE already thanked me by purchasing the work. I'm

    pleased that you're finding it useful.



    Bob . . .

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 12, 2007 6:15 pm Post subject: 1 Amp Fuses

At 09:06 PM 9/12/2007 -0400, you wrote:



 	  Quote: 	
		  

<terrence_miles(at)hotmail.com>



Just to toss a little more in the mix about fuses.  I bought a box of fuses

from Harbor Freight about a year ago and went back today for another box.

Their ATC (ATO?) sized (the middle size ones that most of us use) have been

recalled.  Nobody knew any of the circumstances around this decision.  I

thought everyone ought to know.

Terry


	


   A number of wanna-be's in the fuse business have attempted to

   clone the ATC and similar products only to find that the

   simple little fuse was more complex than molding some handy

   metal stamping inside a plastic housing. Folks like Cooper-

   Bussman and Littlefuse have been in this business for a

   very long time and have optimized the recipe for success

   in the creation of a product that performs as advertised.

   You're never treading at the edge by purchasing devices

   with these brands on them.



   Bob . . .

hooverra(at)verizon.net
Guest

Posted: Wed Sep 12, 2007 6:18 pm Post subject: 1 AMP Fuses

Littlefuse lists 1A minimum in the 257 series ATO fuses and 2A minimum 

in the 297 mini series.



-- 

Ralph C. Hoover

RV7A 

hooverra at verizon dot net

Littlefuse_297.pdf

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Littlefuse_257.pdf

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cjensen(at)dts9000.com
Guest

Posted: Thu Sep 13, 2007 6:09 am Post subject: 1 Amp Fuses

The Chinese are building the old style fuse boxes with the screw in

fuses.  They were having trouble making the screw in fuses that fit in

the fuse box.  Every resourceful, they decided to supply each fuse

socket with a penny on a string.  This is considered an upgrade since

the screw in fuse would only carry 5 amps but the penny...much more.

Distributed by Mattel.  



Chuck

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