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LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Sun Jan 14, 2007 6:36 pm Post subject: 8AWG Wire to Fast-On Connection

In order to keep the voltage drop down on a long 14 volt 30 amp run I 

want to use 8 AWG wire.  The final device has a male Fast-On terminal.  

The only terminals I can find for 8 AWG wire are ring terminals, how do 

I transition to a Fast-On?



Larry

RV-10

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Larry Rosen
#40356
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Posted: Sun Jan 14, 2007 10:24 pm Post subject: 8AWG Wire to Fast-On Connection

At 09:28 PM 1/14/2007 -0500, you wrote:



 	  Quote: 	
		  



In order to keep the voltage drop down on a long 14 volt 30 amp run I want 

to use 8 AWG wire.  The final device has a male Fast-On terminal.

The only terminals I can find for 8 AWG wire are ring terminals, how do I 

transition to a Fast-On?


	


   Splice a 6" 10AWG stub on the end of the 8AWG wire

   so that you can crimp a standard yellow (10-12AWG)

   PIDG on the end.



   30A is pushing a Fast-On pretty hard. What's your

   application?



   Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Tue Jan 16, 2007 7:32 pm Post subject: 8AWG Wire to Fast-On Connection

Bob,

The Fast-On connection is to a mosfet switch solid state relay sold by 

perihelion design <http://www.periheliondesign.com/powerlinkjr.htm> 

rated for 35 amps continuous.  But your statement "30A is pushing a 

Fast-On pretty hard" got me thinking, which generated more questions, so 

now I need some guidance.



I am using the a Z-13/20 architecture that is modified for a battery in 

the tail cone (RV-10)  The solid state relay is for the endurance bus 

feed.  The circuit goes from the battery to a 30 amp ANL limiter to the 

relay and then to the endurance bus, the run is 17 feet.  The continuous 

e-bus load is just under 10 amps, but the maximum possible load is 30 

amps (no diversity at all, everything running at once, flaps, auto pilot 

servos, com transmit, etc).  The drivers for the high load are pitot 

heat and landing light. [I know it could be debated whether or not these 

deserve to be on the e-bus, but IMHO this design is to allow me to fly 

safely in IMC and land]



So, if my calculations are correct for a 14 volt system:

a] 10 amps (at) 17 feet 10AWG has a voltage drop of 0.17 volts

b] 10 amps (at) 17 feet 8 AWG has a voltage drop of  0.11 volts

c] 30 amps (at) 17 feet 10 AWG has a voltage drop of 0.51 volts

d] 30 amps (at) 17 feet 8 AWG has a voltage drop of  0.32 volts



This is only the voltage drop to the e-bus fuse block and does not 

account for the voltage drop to the final device.



So, I believe I am justified in using a 30 amp fuse, but am I being way 

to conservative in using 8 AWG wire to account for a very unlikely full 

max load?



Larry

RV-10 N205EN (reserved)



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



 At 09:28 PM 1/14/2007 -0500, you wrote:



> 

> <LarryRosen(at)comcast.net>

>

> In order to keep the voltage drop down on a long 14 volt 30 amp run I 

> want to use 8 AWG wire.  The final device has a male Fast-On terminal.

> The only terminals I can find for 8 AWG wire are ring terminals, how 

> do I transition to a Fast-On?



   Splice a 6" 10AWG stub on the end of the 8AWG wire

   so that you can crimp a standard yellow (10-12AWG)

   PIDG on the end.



   30A is pushing a Fast-On pretty hard. What's your

   application?



   Bob . . .

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Larry Rosen
#40356
N205EN (reserved)
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Guest

Posted: Wed Jan 17, 2007 7:08 am Post subject: 8AWG Wire to Fast-On Connection

At 10:30 PM 1/16/2007 -0500, you wrote:



 	  Quote: 	
		  



Bob,

The Fast-On connection is to a mosfet switch solid state relay sold by 

perihelion design <http://www.periheliondesign.com/powerlinkjr.htm> rated 

for 35 amps continuous.  But your statement "30A is pushing a Fast-On 

pretty hard" got me thinking, which generated more questions, so now I 

need some guidance.



I am using the a Z-13/20 architecture that is modified for a battery in 

the tail cone (RV-10)  The solid state relay is for the endurance bus 

feed.  The circuit goes from the battery to a 30 amp ANL limiter to the 

relay and then to the endurance bus, the run is 17 feet.  The continuous 

e-bus load is just under 10 amps, but the maximum possible load is 30 amps 

(no diversity at all, everything running at once, flaps, auto pilot 

servos, com transmit, etc).  The drivers for the high load are pitot heat 

and landing light. [I know it could be debated whether or not these 

deserve to be on the e-bus, but IMHO this design is to allow me to fly 

safely in IMC and land]


	


  I'll suggest that nobody should plan to depend on a battery-feed

  e-bus to extract themselves from an IMC environment. In

  retrospect, I'm not too happy with the 13/20 configuration,

  it's pretty messy. I'm beginning to think that Z-12 is the

  best way to incorporate the SD-20 . . . this is how it's

  done on thousands of TC aircraft that used to fly routinely

  in IMC with NO second alternator and NO e-bus.



  Given that you have two engine driven power sources, I'll

  recommend that you pare the E-bus down to the minimum endurance loads

  suggested in chapter 17. Likelihood of EVER needing to

  recover from dual alternator failure using the e-bus all the

  way to the ground is exceedingly low and to PLAN for it

  is making your system get a bit messy.



  If you're down to battery only, then the original e-bus

  philosophy is critical to graceful recovery. You can always

  close master contactors during approach to landing

  for recovery. If you're looking at servicing a 30 amp

  load under these conditions, then adding one or two

  contactors at 1A each is insignificant.

 	  Quote: 	
		  So, if my calculations are correct for a 14 volt system:

a] 10 amps (at) 17 feet 10AWG has a voltage drop of 0.17 volts

b] 10 amps (at) 17 feet 8 AWG has a voltage drop of  0.11 volts

c] 30 amps (at) 17 feet 10 AWG has a voltage drop of 0.51 volts

d] 30 amps (at) 17 feet 8 AWG has a voltage drop of  0.32 volts



This is only the voltage drop to the e-bus fuse block and does not account 

for the voltage drop to the final device.



So, I believe I am justified in using a 30 amp fuse, but am I being way to 

conservative in using 8 AWG wire to account for a very unlikely full max load?


	


   Let's re-think this a bit and see if we can take

   some weight and operating complexity out of your proposed

   design. This is an excellent case where MORE is NOT BETTER.



   Bob . . .

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Wed Jan 17, 2007 7:12 am Post subject: Re: 8AWG Wire to Fast-On Connection

Larry,



Pushing hardware gets everybody into trouble. Please recalculate this based on my Super-4-CCA. Also, have you looked at the ground return? Pushing 30A makes me concerned with ground return currents through the control cables or structural parts...an insidious killer. 



As for the Fastons. I puzzled over this for years. Connectors are sold for 10 AWG wires but no larger, and that firmly sets the amp limit. Splicing larger wires to the connectors concerns me and I advise against it.



Email me offline and we can discuss some options.



(I will still send a sample of Super-2 and Super-4-CCA to interested parties...see my website).

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www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckollsr(at)cox.net
Guest

Posted: Wed Jan 17, 2007 8:37 am Post subject: 8AWG Wire to Fast-On Connection

At 07:12 AM 1/17/2007 -0800, you wrote:



 	  Quote: 	
		  



Larry,



Pushing hardware gets everybody into trouble. Please recalculate this 

based on my Super-4-CCA. Also, have you looked at the ground return? 

Pushing 30A makes me concerned with ground return currents through the 

control cables or structural parts...an insidious killer.


	


   Hmmmm . . . I'm not aware of any well considered

   design situation where local grounding was discouraged

   for the protection of control cables or structural

   parts. We ground things ALL OVER the airframes on

   everything from A36 to Hawker 850 and with return

   currents that run a lot more than 30A.



   I've heard a variety of stories but none were supported

   by any critical review of hard data. Until we're

   offered good data supported by simple-ideas, I'll

   suggest that the eroded cables, loose rivets and

   pitted skins are the result of some stresses OTHER

   than ground return currents.



   For example, a few years ago we identified a case where

   drive-end bearings on starter generators were being

   eroded by small voltage drops in structure (tens of

   millivolts) but at hundreds of amps. This was supported

   by good data, repeatable experiments and obvious

   mitigation of a recurring problem by electrically

   insulating one end of the quill shaft. It would have

   been much BETTER to re-arrange some wiring but the

   cost of modifying hundreds of airplanes was reduced by

   building a special drop-in replacement for the

   starter-generator.



 	  Quote: 	
		  As for the Fastons. I puzzled over this for years. Connectors are

sold for 10 AWG wires but no larger, and that firmly sets the amp limit.


	


   My design philosophy for the use of Fastons has more

   to do with longevity than for "ratings". Yes, one might

   safely assume that 'cause AMP supplies a Faston to fit

   a 10AWG wire, that the same Faston and it's mating

   tab are capable of carrying the same current as the

   wire.



   But keep in mind that wire current "ratings" are based

   on temperature rise . . . a 10AWG wire is not in danger

   in a room temperature environment at 50 amps. Should we

   out-of-hand assume that it's okay to load the 10AWG

   Faston to 50A in the same environment?



   Probably okay when new but consider the case of the

   bouncing ammeters in many Cessna and Piper singles.

   This is a case where multitudinous connections in

   the voltage-sense/field-supply lead have increased

   loop resistance by perhaps 100 milliohms. Not enough

   voltage drop to case the system to fail . . . but enough

   to upset the voltage regulator's servo loop stability.



   This takes perhaps 20-30 years in the field. EXCEEDINGLY

   difficult to diagnose if you don't understand the simple-

   ideas behind system functionality.



   This is why I de-rate the fuse blocks to 15A per slot

   while the manufacturer rates them for 30A per slot.

   Recall that heating effects are an I-squared effect.

   Limiting the design loads on any one fuse by 50%

   reduces heating stresses on the fuses connections by

   75%.  This is a element of an overall design philosophy

   that has nothing to do with things you read in the

   manufacturer's data sheets.



   As I write these words, I'm in conversation with some

   poor tech in Europe trying to fix a paralleling stability

   problem on a 30 year old Hawker. This beast uses

   MAGNETIC AMPLIFIERS in the generator control units.

   The paralleling system has 30-50 joints in the loop . . .

   ANY or ALL of which can be contributing to the malfunction.

   The sad part is that we may find that LOTS of joints need

   to be renewed to bring this airplane back to designed

   performance. This is a case were the joints are carrying

   perhaps less than 3A.



   Just one of many examples of a situation where loading

   decisions and architectures are fine-tuned NOT to

   accommodate out-of-the-box ratings but to reduce

   probability of disappointing performance 10-20 years from now.



   The question that started this thread had to do with

   running an 30A e-bus feeder through a Faston . . .

   all the bells went off and red flags went up. Assume

   this system checks out just fine for first flight

   and then sits quietly waiting for the a some years

   hence when its called upon to perform its intended

   purpose. How much are we willing to bet that it's

   going to take this 30A load for long enough to get

   down? If you're betting your life on it, would

   it not be more prudent to design this potential weakness

   out from square one? This seems especially smart when

   that one joint becomes single point of failure for

   the e-bus alternate feed.

 	  Quote: 	
		    Splicing larger wires to the connectors concerns me and I advise against it.


	


   Keep in mind that the wire was up-sized to meet a voltage

   drop requirement, not to increase max current in the

   line. Splicing "too-big" wires in for the purpose

   of mitigating voltage drop is a sound principal (See

   chapter 8 in 'Connection) but maybe not practical after

   we consider the big picture for system architecture and

   the failure modes we're proposing to handle.



   I'm about 80% convinced that Z-13/20 is going to come out

   of Rev 12 in favor of recommending Z-12 as the most

   practical way to incorporate the SD-20 into a light

   aircraft.



   Bob . . .

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LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Wed Jan 17, 2007 9:55 am Post subject: 8AWG Wire to Fast-On Connection

Thanks Bob and Eric for your guidance.    I will need to rethink my load analysis once again.



Bob,

You said " I'm about 80% convinced that Z-13/20 is going to come out

   of Rev 12 in favor of recommending Z-12 as the most

   practical way to incorporate the SD-20 into a light

   aircraft."



But, doesn't this defeat the elegance of the e-bus concept.  The main alternator fails and with 3 switches (Aux Alternator on, e-bus feed on and master off) you would have an electrical design that would out last the fuel on board.  With Z-12 you would have to manually shed the load.



Larry

 -------------- Original message ----------------------

From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>

 	  Quote: 	
		   

 <nuckollsr(at)cox.net>

 

 At 10:30 PM 1/16/2007 -0500, you wrote:

 

 >

 >

 >Bob,

 >The Fast-On connection is to a mosfet switch solid state relay sold by 

 >perihelion design <http://www.periheliondesign.com/powerlinkjr.htm> rated 

 >for 35 amps continuous.  But your statement "30A is pushing a Fast-On 

 >pretty hard" got me thinking, which generated more questions, so now I 

 >need some guidance.

 >

 >I am using the a Z-13/20 architecture that is modified for a battery in 

 >the tail cone (RV-10)  The solid state relay is for the endurance bus 

 >feed.  The circuit goes from the battery to a 30 amp ANL limiter to the 

 >relay and then to the endurance bus, the run is 17 feet.  The continuous 

 >e-bus load is just under 10 amps, but the maximum possible load is 30 amps 

 >(no diversity at all, everything running at once, flaps, auto pilot 

 >servos, com transmit, etc).  The drivers for the high load are pitot heat 

 >and landing light. [I know it could be debated whether or not these 

 >deserve to be on the e-bus, but IMHO this design is to allow me to fly 

 >safely in IMC and land]

 

   I'll suggest that nobody should plan to depend on a battery-feed

   e-bus to extract themselves from an IMC environment. In

   retrospect, I'm not too happy with the 13/20 configuration,

   it's pretty messy. I'm beginning to think that Z-12 is the

   best way to incorporate the SD-20 . . . this is how it's

   done on thousands of TC aircraft that used to fly routinely

   in IMC with NO second alternator and NO e-bus.

 

   Given that you have two engine driven power sources, I'll

   recommend that you pare the E-bus down to the minimum endurance loads

   suggested in chapter 17. Likelihood of EVER needing to

   recover from dual alternator failure using the e-bus all the

   way to the ground is exceedingly low and to PLAN for it

   is making your system get a bit messy.

 

   If you're down to battery only, then the original e-bus

   philosophy is critical to graceful recovery. You can always

   close master contactors during approach to landing

   for recovery. If you're looking at servicing a 30 amp

   load under these conditions, then adding one or two

   contactors at 1A each is insignificant.

 

 

 >So, if my calculations are correct for a 14 volt system:

 >a] 10 amps (at) 17 feet 10AWG has a voltage drop of 0.17 volts

 >b] 10 amps (at) 17 feet 8 AWG has a voltage drop of  0.11 volts

 >c] 30 amps (at) 17 feet 10 AWG has a voltage drop of 0.51 volts

 >d] 30 amps (at) 17 feet 8 AWG has a voltage drop of  0.32 volts

 >

 >This is only the voltage drop to the e-bus fuse block and does not account 

 >for the voltage drop to the final device.

 >

 >So, I believe I am justified in using a 30 amp fuse, but am I being way to 

 >conservative in using 8 AWG wire to account for a very unlikely full max load?

 

    Let's re-think this a bit and see if we can take

    some weight and operating complexity out of your proposed

    design. This is an excellent case where MORE is NOT BETTER.

 

    Bob . . .

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_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

nuckollsr(at)cox.net
Guest

Posted: Wed Jan 17, 2007 11:27 am Post subject: 8AWG Wire to Fast-On Connection

At 05:53 PM 1/17/2007 +0000, you wrote:



 	  Quote: 	
		  



Thanks Bob and Eric for your guidance.    I will need to rethink my load 

analysis once again.



Bob,

You said " I'm about 80% convinced that Z-13/20 is going to come out

    of Rev 12 in favor of recommending Z-12 as the most

    practical way to incorporate the SD-20 into a light

    aircraft."



But, doesn't this defeat the elegance of the e-bus concept.  The main 

alternator fails and with 3 switches (Aux Alternator on, e-bus feed on and 

master off) you would have an electrical design that would out last the 

fuel on board.


	


   Absolutely . . .



 	  Quote: 	
		     With Z-12 you would have to manually shed the load.


	


   . . . and there are features in the SB-1 regulator that assists

   the pilot in the load reduction task.



   I'm going to catch a lot of flack when I pull the drawing. No doubt

   many folks have installed it . . . and I'll have to explain that

   there's nothing functionally BAD about Z-13/20. Nonetheless, after

   working with builders over the time the drawing has been published,

   I've determined that it doesn't conform to my personal standards

   of "the best we know how to do."  It's simply too complex.



   Bob . . .

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ryan42

Joined: 06 Jul 2006
Posts: 14

Posted: Fri Mar 16, 2007 4:10 pm Post subject: Re: 8AWG Wire to Fast-On Connection

Out of curiosity Bob, would you then mainly advocate z-14 for new designs with a 20A alternator.  In the past it seems you have suggested z-14 over z-12 for people in the planning stages (correct me if I'm wrong).  Maybe a z-14 that uses the second bus as a smaller main alt. out e-bus, not used for starting...smaller battery...



In what instance would you use z-12 over z-14 with a 20A alternator? Save a little $ and #?



-Ryan (In the pondering stage)

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