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Z-11 Questions

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grjtucson

Joined: 07 Apr 2008
Posts: 7
Location: Tucson, AZ

Posted: Fri Dec 05, 2008 5:14 pm Post subject: Z-11 Questions

Hello Listers,



A few questions for my RV-7, Z-11 system, E-Mag/P-Mag.



1. Can I run the Main Bus feed from the Alternator side of the ANL60 Current Limiter? The wiring run would be slightly easier and there's a secondary reason...



2. If I can do #1, would that provide sufficient protection for the 8AWG feed line to the Main Bus? That feed has no protection in Z-11 and it seems like it should.  I foresee little risk of that line shorting to ground, but the consequences would be significant.



3. If I can't do #1, can I / should I use a 12AWG fusible link to protect the Main Bus feed line?



4. My Battery Bus feed line will exceed 6". It's roughly the same run length as the Main Bus feed, something like 24". Can I / should I protect it with a fusible link? Same rationale as the Main Bus feed. It would be a 14AWG run (Battery bus is source for the E-Bus Alt Feed) with an 18AWG fusible link.



5. This is more FYI and for comment, but I'm wiring my E-Mag and P-Mag each the same way:

- E-Bus to 2A panel breaker to mag for power

- SPST switch and shielded P-lead for each mag



My thinking is that they should be wired identically and treated much the same as mags. Powered up on the E-Bus 'cuz they're important, the individual breakers will allow me to power down the P-Mag to test it, and finally the shielded P-leads allow me to switch to traditional mags if ever needed. It is far less complicated than many schemes I've seen and uses cheaper switches (albeit two pricey panel breakers). Any holes in my plan?



6. Finally, is there any problem with feeding those panel breakers through a fuse on the E-Bus? My only other panel breaker, the Field, will be fed through a fusible link from the Main Bus screw terminal.



Thanks in advance,



George Jenson

Tucson, AZ

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_________________
George Jenson - http://www.georgejenson.com
Tucson, AZ - RV-7 Standard Build
Empennage Completed 1/06
Wings Completed 11/06
Fuselage in Progress

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 06, 2008 6:32 am Post subject: Z-11 Questions

At 07:14 PM 12/5/2008, you wrote:

 	  Quote: 	
		  



Hello Listers,



A few questions for my RV-7, Z-11 system, E-Mag/P-Mag.



1. Can I run the Main Bus feed from the Alternator side of the ANL60 

Current Limiter? The wiring run would be slightly easier and there's 

a secondary reason...


	




    How about the system side of the ANL? The reason

    the ANL would open is because of a fault in the

    alternator or its feeder. This is an exceedingly

    rare event but it would take down the whole system

    if you feed from the alternator side.



 	  Quote: 	
		  2. If I can do #1, would that provide sufficient protection for the 

8AWG feed line to the Main Bus? That feed has no protection in Z-11 

and it seems like it should.  I foresee little risk of that line 

shorting to ground, but the consequences would be significant.


	


    FAT wires in airplanes that feed large busses

    and connect starters and batteries together do not

    require protection. You won't find such protection

    in any certified light aircraft. Here's an excerpt

    from FAR23



http://www.aeroelectric.com/Reference_Docs/FAA/Part23_electrical_A.pdf



    Check out paragraph 23.1357 . . .

 	  Quote: 	
		  3. If I can't do #1, can I / should I use a 12AWG fusible link to 

protect the Main Bus feed line?


	


    Not useful . . .

 	  Quote: 	
		  4. My Battery Bus feed line will exceed 6". It's roughly the same 

run length as the Main Bus feed, something like 24". Can I / should 

I protect it with a fusible link? Same rationale as the Main Bus 

feed. It would be a 14AWG run (Battery bus is source for the E-Bus 

Alt Feed) with an 18AWG fusible link.


	


    No, that 6" thing is a design goal. The world does

    not spin down to a halt if it is longer. Treat this

    feeder with the same concerns for design, installation,

    and maintenance as your prop bolts. Satisfy yourself

    that there is NO way this wire's functionality can

    become compromised.

 	  Quote: 	
		  5. This is more FYI and for comment, but I'm wiring my E-Mag and 

P-Mag each the same way:

- E-Bus to 2A panel breaker to mag for power


	


 	  Quote: 	
		  - SPST switch and shielded P-lead for each mag



My thinking is that they should be wired identically and treated 

much the same as mags. E-Bus 'cuz their important, the individual 

breakers will allow me to power down the P-Mag to test it, and 

finally the shielded P-leads allow me to switch to traditional mags 

if ever needed. It is far less complicated than many schemes I've 

seen and uses cheaper switches (albeit two pricey panel breakers). 

Any holes in my plan?


	


    The switching arrangements shown in Z-11 for Emagair

    products are consistent with their recommendations

    and consideration of the effects of possible failure

    modes. This is your airplane . . . if you have comfort

    requirements that go beyond these recommendations, by

    all means, address them.



 	  Quote: 	
		  6. Finally, is there any problem with feeding those panel breakers 

through a fuse on the E-Bus? My only other panel breaker, the Field, 

will be fed through a fusible link from the Main Bus screw terminal.


	


    Breakers fed with like sized fuses will never operate.

    The fuses are 10x or more faster than breakers. You might

    as well use switches . . . which are already part of the

    suggested design. If you have a desire to incorporate

    breakers, then the battery bus fuses need to up-size to

    30A devices and the feeder wire from bus to breaker

    should up-size to 14AWG or so.



    It's my recommendation that you wire the airplane as

    suggested in Z-11. This architecture was developed

    over 15 or so years of considerations for the uniqueness

    of the OBAM aircraft community based on 40+ years

    of experience in the TC aircraft world. Changes can and

    should be made if you find the recommendations lacking in

    some way for (1) minimizing weight, parts count and/or cost,

    (2) operational convenience or (3) safety. In these

    cases proposed changes should be evaluated by everyone as

    a candidate for revising Z-11 as published.



    But it's your airplane . . . your safest operational

    mode requires that you need to fly it with comfort

    and understanding.

    Bob . . .

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grjtucson

Joined: 07 Apr 2008
Posts: 7
Location: Tucson, AZ

Posted: Sun Dec 07, 2008 9:42 am Post subject: Re: Z-11 Questions

Bob,



I'll wire per Z-11 on the bus feeds, thanks for the lesson and illumination.



I am, however, going to wire per E-Mag Air on the mags. For the power feeds, E-Mag calls for a breaker for the E-Mag and a switch and breaker for the P-Mag, optionally combining the switch and breaker. I'm just going to use breakers for both, pulling the P-Mag's when I test it's generator. I prefer the simplicity of a SPST switch consistently used for both, and should I ever switch to standard mags, I just delete my panel breakers.



I will feed the breakers from the terminal of the E-bus, not through a fuse.



BTW, the present revision M of Z-13/8 has the P-Mag generator unable to be tested (open P-Lead and no power) short of powering down the Main bus. I'd think having the P-Mag get a 3 pos. switch as you had on Rev L would be superior. The P-Mag would then be Off-On-Bat and the E-Mag would be Off-Bat-On, and you could feed both from the Battery Bus.



Also, for what it's worth, E-Mag Air does call for 18AWG feeders and grounds, contrary to the Z diagrams.



Thanks for doing what you do 



George

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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_________________
George Jenson - http://www.georgejenson.com
Tucson, AZ - RV-7 Standard Build
Empennage Completed 1/06
Wings Completed 11/06
Fuselage in Progress

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Dec 07, 2008 9:58 am Post subject: Z-11 Questions

At 11:42 AM 12/7/2008, you wrote:

 	  Quote: 	
		  



Bob,



I'll wire per Z-11 on the bus feeds, thanks for the lesson and illumination.



I am, however, going to wire per E-Mag Air on the mags. For the 

power feeds, E-Mag calls for a breaker for the E-Mag and a switch 

and breaker for the P-Mag, optionally combining the switch and 

breaker. I'm just going to use breakers for both, pulling the 

P-Mag's when I test it's generator. I prefer the simplicity of a 

SPST switch consistently used for both, and should I ever switch to 

standard mags, I just delete my panel breakers.



I will feed the breakers from the terminal of the E-bus, not through a fuse.



BTW, the present revision M of Z-13/8 has the P-Mag generator unable 

to be tested (open P-Lead and no power) short of powering down the 

Main bus. I'd think having the P-Mag get a 3 pos. switch as you had 

on Rev L would be superior. The P-Mag would then be Off-On-Bat and 

the E-Mag would be Off-Bat-On, and you could feed both from the Battery Bus.


	


    Given that there are two ignition systems with a high

    degree of reliability  . . . either one of which runs

    the engine just fine . . . Emagair told me that there

    was very little to be gained by frequent testing of

    the E-Mag's self supporting capabilities. They suggested

    a couple of times a year. This is easy to do at the same

    time you deliberately drop the main bus to do battery-only

    endurance verifications or what-ever. The point is that

    the system wired as shown CAN be tested by the pilot either

    in pre-flight or during flight with the controls configured

    as shown.



    As shown, one achieves automatic load-shedding of the

    E-mag during battery-only ops because IT IS fed from

    the main bus.

 	  Quote: 	
		  Also, for what it's worth, E-Mag Air does call for 18AWG feeders and 

grounds, contrary to the Z diagrams.


	


    Yeah, not necessary from the perspective of operating physics.

    It's a mechanical robustness thing.

 	  Quote: 	
		  Thanks for doing what you do 


	


    My pleasure sir. I'm pleased that you receive good

    value from the effort.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

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