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Questions on Z-16 Diagram

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txpilot

Joined: 26 Feb 2007
Posts: 87
Location: Houston, TX

Posted: Sat Nov 03, 2007 11:31 pm Post subject: Questions on Z-16 Diagram

Hello,

I'm currently building a Zenith CH-701 with a Rotax 912S.  I'm using the Z-16 revision M schematic as a guide for designing my electrical system.  I'm afraid I'm struggling a bit on understanding this diagram and have a few questions.



1.  The schematic shows the start switch connected to a starter contactor which I assume would be B&C part S702-1.  I'm using an ACS A-510-2 ignition switch.  Can this start switch be directly connected to the starter relay supplied by Rotax, or will I need to purchase S702-1 and run it in series with the supplied starter relay?  Do I need to worry about excessive wear on the start switch contacts if I directly connect the start switch to the Rotax starter relay?



2.  I'm trying to understand the overvoltage protection.  Correct me if I'm wrong, but I believe this is the sequence if the voltage regulator fails:



   A.  Crowbar Overvoltage Module senses the overvoltage condition.  Creates a 'short' from alternator master switch to ground.



   B.  Alt breaker responds to the short by tripping, thus de-energizing alternator OV disconnect relay.



   C.  Alternator OV relay opens circuit from alternator (yellow AC wires), thus removing the alternator from the system.



3.  Assuming I'm right on number 2, I'm confused on the N.C. and N.O. terminology.  I thought an energized relay circuit would be considered 'normally closed', but according to the diagram that would open the circuit and take the alternator off line.  I don't mean to get too wrapped up on the terminology, but I want to make sure I understand what I'm doing here.



Thanks in advance for any advice.



Best Regards,



Dan Ginty

Gilles.Thesee(at)ac-greno
Guest

Posted: Sun Nov 04, 2007 4:23 am Post subject: Questions on Z-16 Diagram

txpilot a écrit :



Dan,



I wired two airplanes using Fig Z16 with no problem.



 	  Quote: 	
		   1. Can this start switch be directly connected to the starter relay supplied by Rotax,

You can use the Rotax starter relay. Make sure to add a diode or else 
	


across the coil.



 	  Quote: 	
		   3.  Assuming I'm right on number 2, I'm confused on the N.C. and N.O. terminology.  I thought an energized relay circuit would be considered 'normally closed'

   

Most relays have 'normally open' and 'normally closed' contacts. That 
	


tells us which contacts are closed or open when *de-energized*. You 

chose which set of contact you want to use.

You may wish to look at the relay documentation to identify which 

contacts are which, otherwise you can use a multimeter.



Best regards,

-- 

Gilles

http://contrails.free.fr

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sun Nov 04, 2007 8:34 am Post subject: Questions on Z-16 Diagram

Dan;

  

 "Normal" with respect to switch or relay contacts  means just that, "normal", "most of the time", "as sitting on the shelf" ,  etc.  The opposite of "normal" is the activated or energised state  where power is applied to the relay coil, the switch is activated, etc and the  contacts transfer to the opposite position.

  

 Bob McC

  

  

 [b]---

_________________
Bob McC
Falco #908
(just starting)

txpilot

Joined: 26 Feb 2007
Posts: 87
Location: Houston, TX

Posted: Mon Nov 05, 2007 12:10 pm Post subject: Re: Questions on Z-16 Diagram

OK.  That makes sense.  Thanks for clarifying it.



Two other questions come to mind:  is the CB really necessary if there's also a fuse in series?  After reading the Aeroelectric Connection, Bob has me sold on fuses and I didn't plan on adding any breakers to my panel.



Second, regarding E-bus Alternate feed switch, is it a good idea to make that a guarded switch?  I would hate for that switch to be accidentally left on overnight and thus draining the battery.



Thanks,



Dan Ginty

nuckolls.bob(at)cox.net
Guest

Posted: Mon Nov 05, 2007 5:39 pm Post subject: Questions on Z-16 Diagram

At 12:10 PM 11/5/2007 -0800, you wrote:



 	  Quote: 	
		  



OK.  That makes sense.  Thanks for clarifying it.



Two other questions come to mind:  is the CB really necessary if there's 

also a fuse in series?  After reading the Aeroelectric Connection, Bob has 

me sold on fuses and I didn't plan on adding any breakers to my panel.


	


    I presume you're speaking of the alternator control

    feeder to a breaker that is upstream of a crowbar

    ov protection module. There's a fusible link which is

    not really a fuse but a concession to traditional

    notion in the T/C aircraft world for "protecting"

    longer than 6". If you use some other ov protection

    scheme, you could leave the breaker out and just

    run the alternator field from a standard fuse

    on the block. One choice would be using the AEC9011

    generator/alternator OV relay feature. This

    eliminates the need for a breaker.



    It's not practical to use a fuse upstream

    of a breaker . . . crow-barring a 5A breaker

    will pop a 20A fuse, hence the fusible link

    with a very robust I-squared*T fusing constant

    in comparison with the breaker.



 	  Quote: 	
		  Second, regarding E-bus Alternate feed switch, is it a good idea to make 

that a guarded switch?  I would hate for that switch to be accidentally 

left on overnight and thus draining the battery.


	


    Have your low oil pressure warning light run

    from the e-bus . . . or buzzer. If the engine

    is not running and the e-bus is up, it notifies

    you. But then, one can use guards on any switch

    in the airplane. Are there not things on the

    e-bus that would stay lit-up as sufficient

    warning? My personal preference is making it

    a checklist item. Except for pre-flighting the

    e-bus alternate feed switch, there's no reason

    to turn it on except in case of alternator

    failure . . . hence probability of accidental

    failure to turn off at end of flight is

    considerably reduced.



    Bob . . .

vozzen

Joined: 25 Aug 2006
Posts: 12

Posted: Mon Nov 05, 2007 8:14 pm Post subject: Re: Questions on Z-16 Diagram

Along these same Z-16 lines (Jabiru/Rotax with 20 amp AC generator)...



Is it any problem for the regulator  if it's control ("sense") is fed from the same circuit breaker as the OV module ( and OV-relay coil)?   



In other words, if the OV relay trips (breaking the AC line between the alternator and regulator), the "sense" line to the regulator opens, dropping the control voltage into the regulator to zero.  Is this a problem?



Would there be any advantage (or disadvantage)  to feeding the regulator control directly from the bus?  



Thanks in advance.

Richard, 601XL/3300

txpilot

Joined: 26 Feb 2007
Posts: 87
Location: Houston, TX

Posted: Tue Nov 06, 2007 11:57 am Post subject: Re: Questions on Z-16 Diagram

 	  Quote: 	
		  If you use some other ov protection 

scheme, you could leave the breaker out and just 

run the alternator field from a standard fuse 

on the block. One choice would be using the AEC9011 

generator/alternator OV relay feature. This 

eliminates the need for a breaker. 	




Thanks, Bob.  I'll just stick with the crowbar OV protection in the Z-16 diagram.  I just ordered everything I need from B&C.  Now all I need is a good fire extinguisher.  



Dan

nuckolls.bob(at)cox.net
Guest

Posted: Tue Nov 06, 2007 7:55 pm Post subject: Questions on Z-16 Diagram

At 08:14 PM 11/5/2007 -0800, you wrote:



 	  Quote: 	
		  



Along these same Z-16 lines (Jabiru/Rotax with 20 amp AC generator)...



Is it any problem for the regulator  if it's control ("sense") is fed from 

the same circuit breaker as the OV module ( and OV-relay coil)?



In other words, if the OV relay trips (breaking the AC line between the 

alternator and regulator), the "sense" line to the regulator opens, 

dropping the control voltage into the regulator to zero.  Is this a problem?



Would there be any advantage (or disadvantage)  to feeding the regulator 

control directly from the bus?


	


    Depending on who's rectifier/regulator is being

    used, there may be manufacturer's prohibitions

    for connection of "C" to the bus independently

    of B and R. Having said that, and based on what

    I've seen of what's reputed to be an exemplar

    schematic of this genre' of rectifier/regulator,



(See: http://www.aeroelectric.com/Pictures/Regulators/regul_912.jpg)



    I can perceive no reason in the physics for

    this prohibition. But unless provided with

    a lucid schematic of the specific device

    in question, I cannot refute the prohibition

    with confidence. Hence the drawing you see

    in Z-16.



    What problems have you deduced for wiring

    as suggested?



    Bob . . .



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

        ( "Problems are the price of progress. )

        ( Don't bring me anything but trouble. )

        ( Good news weakens me."               )

        (              -Charles F. Kettering-  )

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

vozzen

Joined: 25 Aug 2006
Posts: 12

Posted: Wed Nov 07, 2007 1:15 pm Post subject: Re: Questions on Z-16 Diagram

>What problems have you deduced for wiring

as suggested?



None-- looks great.    I was using the outdated Rev.K, which showed C-lead coming thru the OV trip breaker circuit, instead of direct from battery (via Master Sw).



Thanks, Bob,  for your continuing attention.

nuckolls.bob(at)cox.net
Guest

Posted: Wed Nov 07, 2007 4:14 pm Post subject: Questions on Z-16 Diagram

At 01:15 PM 11/7/2007 -0800, you wrote:



 	  Quote: 	
		  



 >What problems have you deduced for wiring

as suggested?



None-- looks great.    I was using the outdated Rev.K, which showed C-lead 

coming thru the OV trip breaker circuit, instead of direct from battery 

(via Master Sw).



Thanks, Bob,  for your continuing attention.


	


   No problem . . . and I wasn't trying to challenge you

   on the 'modification' . . . I'm just trying to be

   sensitive to errors in my perceptions and

   evolution in new products.



   Bob . . .

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