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B-lead protection

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aaaron(at)tvp.com.au
Guest

Posted: Wed Jul 31, 2013 5:43 am Post subject: B-lead protection

I'm finishing the wiring in my safari helicopter and need some advice re B-lead ANL or fuse.  I'm using the skytec starter with built in solenoid with about 3 feet of number 2 wire going from the starter to the master contactor.  I'm using a tractor style push-button starter switch and an externally regulated 40a alternator. Since I have no external starter contactor, do I need to run the B-lead from the alternator via a fuse to the master contactor or can I run it the much shorter length between the alternator and starter? If the former, I could mount the ANL holder on the firewall but I would have three fat wires (starter, B-lead and main bus) bolted to the master contactor.  If I can just connect the alternator to the starter lead I can use an inline fuse holder. My questions are:

1. Where do I put the B-lead and fuse/ANL?

2. What size wire for the B-lead?

3. What size fuse/ANL?

4. Do I need to put a diode across the starter button and if so, which one and in what direction?

Thanks!

Allan

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jul 31, 2013 6:49 am Post subject: B-lead protection

At 08:42 AM 7/31/2013, you wrote:

 	  Quote: 	
		  

I'm finishing the wiring in my safari helicopter and need some 

advice re B-lead ANL or fuse.  I'm using the skytec starter with 

built in solenoid with about 3 feet of number 2 wire going from the 

starter to the master contactor.


	


   #2 is possibly overkill, #4 would certainly suffice

   for your battery/starter wiring.



 	  Quote: 	
		  Since I have no external starter contactor, do I need to run the B-lead

from the alternator via a fuse to the master contactor or can I run it

the much shorter length between the alternator and starter?


	


   Take it to the starter.



 	  Quote: 	
		  1. Where do I put the B-lead and fuse/ANL?


	


   As close as practical to the starter but if

   the fuse ends up in the middle of the wire run,

   it's no big deal.



 	  Quote: 	
		  2. What size wire for the B-lead?


	


   8AWG is fine for 40A alternator.



 	  Quote: 	
		  3. What size fuse/ANL?


	


   I see Walmart is offering this fuse

   in a 30A, which is plenty robust for

   your alternator.



http://tinyurl.com/l6qbxsc



    This is a miniature fuse for which you

    can fabricate your own holder from a piece

    of phenolic and some screws, nuts and washers

    from the hardware store.



 	  Quote: 	
		  4. Do I need to put a diode across the starter button

and if so, which one and in what direction?


	




    Not ACROSS the button but from contactor side

    of button to ground. Cathode connected to pushbutton,

    anode to ground. Any of the 1N5400 series diodes

    from Radio Shack are find. See:



    http://tinyurl.com/l65nqnw



    There was an AD issued against the ACS key-switch

    some years back that put a diode across the switch . . .

    completely ineffective.



    http://tinyurl.com/l6qbxsc



   Diode needs to wire across

    the solenoid coil either at the switch as described

    or on the contactor (probably not as convenient but

    if you can put it there, that's good too.)



   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jul 31, 2013 12:11 pm Post subject: B-lead protection

 	  Quote: 	
		  

 2. What size wire for the B-lead?

 3. What size fuse/ANL? 	




 Here's a 40A MIDI style stocked by Digikey



  http://tinyurl.com/mpudgxu



 and a holder like this



 [img]cid:7.1.0.9.0.20130731150249.020c51e0(at)aeroelectric.com.0[/img] 



 To mount it can be found here . . .



  http://tinyurl.com/kcbyc79



 

 

   Bob . . .

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donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Thu Aug 01, 2013 5:26 am Post subject: Re: B-lead protection

 	  Quote: 	
		   Here's a 40A MIDI style stocked by Digikey



  http://tinyurl.com/mpudgxu



 and a holder like this



 [img]cid:7.1.0.9.0.20130731150249.020c51e0(at)aeroelectric.com.0[/img] 



 To mount it can be found here . . .



  http://tinyurl.com/kcbyc79

	




How do these compare with the ANLs that B&C sells? Other than being a LOT less money?   



Do they have a greater tolerance? Slower speed (of reaction)? Don't last in a harsh enviroment?

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 01, 2013 6:01 am Post subject: B-lead protection

 	  Quote: 	
		  

How do these compare with the ANLs that B&C sells? Other than being 

a LOT less money?  


	


   Here's the data sheet on MIDI fuses



http://tinyurl.com/l985dtj



   Here's the data on ANL . .



http://tinyurl.com/k7o3l3q

 	  Quote: 	
		  Do they have a greater tolerance? Slower speed (of reaction)? Don't 

last in a harsh enviroment?


	


   The ANL has been around for about 80 years

   and is still used in new design. Premier

   was the last airplane we designed with a

   majority DC power system in it. The distribution

   panel contains a goodly number of the ANL style

   limiters.



   The MIDI's have roots in the automotive industries

   where we have witnessed a continuous evolution of

   designs. For example, cartridge glass fusses

   got replaced by ATC plastics which in turn have

   been superceded by the ATR micro fuses. All three

   generations perform to their manufacturer's specs

   and have been found suited to task in billions of

   applications.



   The ANL and MIDI are not drop-in replacements

   for each other as you can deduce from their

   performance curves. But the differences are

   insignificant to our task. The advantage of

   the more modern design is that they are made

   in relatively large quantities on automated

   machines for markets much larger than the

   markets which nurtured the ANL devices.



   Until recently (last 10 years or so) the

   modern replacements for the ANL were not

   as convenient to acquire. You could find

   the fuses as after market service parts but

   holders were more of an OEM item. But now

   that Digikey has partnered with Bussmann

   and Littlefuse to distribute them, procurement

   is much easier.

   Bob . . .

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